Most of us know something about the heat treatment of metals; others know more; but the real experts also know what they don't know. Some terms at an extremely basic level: "ALLOY STEEL" -- a mixture made from molten steel and one or more other metals. If you are lucky, the metal was identified with a code number that tells you the content, and thus you can look up its properties and suitability for your task. If you are unlucky, an unidentified steel will be inappropriate for your use and you will waste a lot of time for nothing. "ANNEALING" -- a heat treatment that reduces the hardness or brittleness of metals and removes internal stresses that could lead to fractures. This process also pertains to metals other than steel. For example, shaping by hammering on a sheet of steel or copper or aluminium or brass or silver makes the metal work-hardened; periodic annealing (heating and then allowing slow cooling) allows the hammering to then continue without cracking until the final form is reached (car fender, silver teapot, whatever). "CASE HARDENING" -- low carbon steels (say under 0.6 %) may not be suitably hardened to the intended use by conventional heat treatment. Case hardening or carburizing is a process to increase the carbon and hardness of the outer skin of the steel part, thus resisting surface wear while retaining a softer, tougher, less brittle core. "HARDENING STEEL" -- a heat treatment process for high-carbon (tool) steel or alloy steel by heating to an appropriate temperature for the particular steel, followed by quenching (sudden cooling in water or dense salt solution or oil, or slow cooling in air) followed by reheating to a lower tempering temperature (where stresses are removed and toughness is increased) and finally recooled. HEAT TREATING ADDITIONAL SAFETY WARNING: While "home" heat treatment as described in some of the messages seems to be relatively simple in concept, the vagaries of alloys and heating equipment and temperature determination and timing make a successful outcome much less than certain. It is potentially a hazardous process to anyone present during the heat treating, and to anyone at risk from the use and/or failure of a critical component that was not properly heat treated. Any decision to engage in heat treating is totally your personal choice, and totally your personal responsibility for any negative consequences. Did you know that many professional metalworking businesses contract out their heat treating to professional heat treatment companies? You could too. If you got to this file directly from my HOME PAGE, return there by using your browser's back button. BUT if you came to this file as the result of a web search engine, see more than 70 additional files on my home page Machining and Metalworking at Home http://www.janellestudio.com/metal/ SAFETY WARNING BEWARE: DO NOT ASSUME that any subject matter or procedure or process is safe or correct or appropriate just because it was mentioned in a news/user group or was included in these files or on this site or on any other web site or was published in a magazine or book or video. Working with metals and machinery and chemicals and electrical equipment is inherently dangerous. Wear safety devices and clothing as appropriate. Remove watches, rings, and jewellery -- and secure or remove loose clothing -- before operating any machine. Read, understand and follow the latest operating procedures and safety instructions provided by the manufacturer of your machine or tool or product. If you do not have those most recent official instructions, acquire a copy through the manufacturer before operating or using their product. Where the company no longer exists, use the appropriate news or user group to locate an official copy. Be careful -- original instructions may not meet current safety standards. Updated safety information and operating instructions may also be available through a local club, a local professional in the trade, a local business, or an appropriate government agency. In every case, use your common sense before beginning or taking the next step; and do not proceed if you have any questions or doubts about any procedure, or the safety of any procedure. Follow all laws and codes, and employ certified or licenced professionals as required by those laws or codes. Hazardous tasks beyond your competence or expertise should also be contracted to professionals. Let's be really careful out there. (c) Copyright 2003 - 2008 Machining and Metalworking at Home The form of the collected work in this text file (including editing, additions, and notes) is copyrighted and this file is not to be reproduced by any means, including electronic, without written permission except for strictly personal use. ========================================================================= Date: Fri, 26 Jan 2001 09:43:37 -0500 From: Larry Richter Subject: Re: Simple heat-treating "Jeffrey C. Dege" wrote: > IRf I was starting from nothing, what would I need to get the > simplest and cheapest setup for heat-treating small parts? A propane torch, a vise grip pliers, some plain sheffield tool steel, a bag of jewelers pumice or a soft firebrick, and a a gallon of salt brine or engine oil. Read the directions on the packing envelope of the tool steel. Heat the steel to the 1450 red point using the pumice or brick to reflect heat and moving the torch a lot. Dip the steel in the quench using the pliers. When the steaming stops, polish the part, heat it until you get straw or light blue colored oxidation, quench it again. Use the tool, maybe break it, refine your ways, be impressed. Maybe get a magnet to test the temperature. ------- Date: Fri, 26 Jan 2001 11:10:45 -0800 From: "Nicholas Carter and Felice Luftschein" Subject: Re: Simple heat-treating I do it the half-assed way: Turn the reamer from drill rod. What type of drill rod? I don't know, I use some scrap that I got that just says "drill rod". Heat until bright red, then quench in oil. I save all the olive & canola oil I use when frying food. Then polish and temper, for one or two time use, it doesn't really matter what temper you draw. Mic the reamer afterwards to make sure it hasn't warped excessively. A 1/4" reamer, is a very useful and inexpensive tool, about $5-$10 depending on what quality you buy. I find I use the 1/4", 3/8" and 1/2" reamers all the time. ------- Date: Sat, 27 Jan 2001 05:58:03 -0800 From: "Delaney, John" Subject: RE: Heat Treat It been a pretty long time now, 1975, but my Jr. High metal shop teacher showed some of us how to heat treat on the cheap. He just used the gas fired forge we had and 30W oil as the quench. We were heat treating hammer faces so we didn't want them too hard, just a little more firm then the mild steel we were working with. We thought the bluing effect was really cool too as I recall. I later had the concept confirmed in a couple of physics classes. So this heat it up and dunk it in something liquid containing a lot of carbon (OIL) is about all there is to it. The one safety tip he did give us was to make sure there wasn't ANY water in the oil. If the hot tool of enough mass hits a water pocket you could get nasty hot oil shower. Something to think about. My Mom still has that hammer and uses it often I understand. Later - jd ------- Date: Sat, 27 Jan 2001 09:56:48 -0500 From: Larry Richter Subject: Re: RE: Heat Treat The process is to heat the steel above a transformation point, usually above 1450F, at which the steel becomes nonmagnetic. Then the steel to be hardened has to be cooled faster than it can transform back. It has to beat its transformation curve on the way down to normal temperature. This freezes the crystal structure in an altered state. Subsequent heating to points below the transformation point will further change the hardness of the steel and its usefulness. Carbon in the quenching medium doesn't change much, but avoiding steam generation in anything dangerous is good. If you are trying to case harden something, to make mild steel absorb an amount of carbon that will aid in hardening it, the presence of carbon in the heating environment is important. ------- Date: Sun, 28 Jan 2001 19:38:23 From: batwingsx~xxi-plus.net Subject: Re: RE: Heat Treat At 05:58 AM 1/27/01 -0800, you wrote: >so we didn't want them too hard, just a little more firm then the mild steel we were working with. We thought the bluing effect was really cool too as I recall. I later had the concept confirmed in a couple of physics classes. So this heat it up and dunk it in something liquid containing a lot of carbon (OIL) is about all there is to it. < That's pretty much a simplification. Mild steel won't harden much if any. The carbon must be donated to the steel by soaking it in a carbon-rich substance while hot, and bone meal is one such, or you would use an alloyed steel made for heat-treat. The oil serves as quench which, in materials which have sufficient carbon, is responsible for cooling the steel so fast it can't go thru the usual phase transforms, so it retains the hard allotropes. You can't get carbon into the steel with the quench, any carbon in it wouldn't possibly have time to permeate the metal. In fact, you can quench steels in oil or water, and some will harden with air cooling. And warping is dependant on the type of quench, worst to best in order given above. Finally, carburizing is only one way to harden steel; nitride case hardening for example forms an intensely hard surface with little dimensional change from the diffusion of nitride into steel, and it needs no quench. Regards, Hoyt ------- Date: Tue, 30 Jan 2001 06:24:13 From: batwingsx~xxi-plus.net Subject: Re: Heat Treat >used for a cutting tool. When you use something like bone meal >to harden the surface what do you do? The steel object is packed with the meal tightly around it. It's best to use commercial products like Casenite. Can be found or referenced from gun shops and machine shops. But for most machine shop purposes tool steels should be used instead of case hardening Any good supply house like MSC can sell you blanks of various steels. >process several times? Would something like charcoal work? Yes, charcoal and coke are excellent for producing a hard case. The procedure is much the same: pack, soak in red heat for a while depending on thickness, quench. You wouldn't repeat, just soak longer if needed. Often the hardness is so extreme you will need to temper back some, by cleaning surface and heating again to show a desired color. If you want to approach heat treat on a basis of avocation, try looking into knife making. I've seen my dad make some fantastic knives out of old files. Buck knives were originally supposed to be made from horse shoe rasps. First you anneal, shape outline, shape cross section. Then you heat, soak, quench and draw. He would use hand torch on back of blade, playing it to make the color advance toward the edge. Used sandpaper as he went to keep getting a fresh reading. When the back was blue and the edge breaking into light straw color, he would unclamp the vise and the blade fell into a bucket of water. This made a blade that was as hard as sin on cutting edge but resilient and supple along the entire length. Dad's knives would shave you! He also made leather laminated handles with stacked rings and hand fitted brass bolsters, scabbards and belts. Some of these were ordinary, but some of them were among the prettiest things you could imagine. ------- Date: Thu, 3 May 2001 20:35:15 -0700 From: "Marcus & Eva" Subject: Re: Re: Cutting tool steel with a sherline mill Hi Jack: Air hardening steels are supplied in the annealed condition (soft) just like oil or water hardening steels. They are hardened by heating and then quenching in an air blast. Heating tool steel alters its crystalline structure; when it is cooled slowly, it usually reverts back to its original crystalline form. If the crystal structure that it had while hot can be preserved, the steel becomes hard. That's what quenching does (there's a lot more to it than that, but this roughly describes what happens). Some alloys of steel rely also on precipitation of carbides in the crystal matrix to stabilize the altered structure. Some of these alloys become tolerant to relatively slow cooling without reverting back to the crystal structure they had when they were still soft. These are the air hardening grades of steel. The relatively slow quench in air results in fewer residual stresses in the steel, so it distorts less. In order to anneal such a steel it must be cooled extremely slowly, and even then, may not go all the way back to a fully softened condition. Cheers Marcus ------- Date: Thu, 3 May 2001 14:15:52 -0700 From: "Yasmiin Davis" Subject: RE: Re: Cutting tool steel with a sherline mill To add a bit more to this there are temperature sensitive markers and I think there is also tape now. Anyway you look up in the good old machinery hand book about how hot you need to get is for a given hardness ( Rockwell # ) and you buy a crayon for that temperature. They have information on the various alloys that are sold as ground stock. Also the vendor can give you a spec sheet on the material. Then you mark the work and heat it up -- when the crayon mark does its thing, then you quench it in the appropriate liquid. Then if you want to get real fancy you heat it up to a lower them for a given length of time to draw the hardness -- that is, make the piece have more strength, or other properties. This is one of the reasons those fancy Japanese tools are so expensive. The maker does all this by the color of the piece as he works it. Yasmiin ------- From: sleykinx~xxa... Date: Wed Jul 18, 2001 7:33 pm Subject: Re: [atlas_craftsman] Re: Sequence of work? (Wendall) 07/18/2001, HUNLEY31... writes: > Any experience taking the > temper out of a ball bearing then making it hard again? Next time you fire up the BBQ tos a few in the coals after you light em and leave em till they are cool again. They won't stay shiny but they will be soft. ------- From: sleykinx~xxa... Date: Wed Jul 18, 2001 8:23 pm Subject: Re: [atlas_craftsman] Quench? In a message dated 07/18/2001, rodumx~xxw... writes: > After grinding a tool I realize that the cutting tip should be heated > cherry red and then quenched to harden...But I have heard several > different quenching methods, involving regular water, salt water, or > motor oil. Thought I would ask the experts for an opinion on which is > best and save myself the frustration of wondering if I got it right... If you are talking about a Carbon Steel bit that is close. If you are talking about High Speed Steel or carbide like most metal lathe bits are made from, no quench. You grind the bit and keep it from getting red hot while you are grinding. Don't cool it in water. (Much discussion on RCM about this point.) Quenching a HSS bit will cause micro fractures and result in poor performance. Good rule of thumb is to hold the bit in your hand while grinding...if you can still hang onto it it isn't too hot. Check the RCM archives on Grinding HSS for a very lengthy discussion of this. Regards Glenn Neff medford, OR ------- From: "jerdal" Date: Thu Jul 19, 2001 12:04 am Subject: Re: [atlas_craftsman] Quench? > After grinding a tool I realize that the cutting tip should be heated > cherry red and then quenched to harden... This is news to me. Almost all cutter blanks are HSS, which as noted in other posts requires no hardening after grinding. Any heating will almost surely damage, not improve them If you are making a carbon steel tool from a piece of raw tool steel (not a blank), it may or may not need to be hardened. If already hardened, grinding as noted for HSS will not draw the temper if you are reasonably careful. If not hardened, it depends on the type of steel, Some are oil hardening, some air. Air hardening you cannot deal with adequately by hand methods. Oil hardening steel, or water hardening drill rod can be hardened if required by heating and quenching in the appropriate quench material. However, usually it is necessary to draw back the temper, especially water hardening material, to atttain the correct hardness allied with toughness. The initial water quench leaves it glass hard, and breakable. It can be drawn back by heating with torch or in an oven. For torch you will need to check the color, for an oven the correct temp will do. I forget the color vs hardness scale, but the colors are on a polished portion of the tool, varying from blue to brown and straw for different temperatures and resulting hardness. Jerry ------- From: dswrx~xxw... Date: Thu Jul 19, 2001 8:32 am Subject: Re: [atlas_craftsman] Quench? Most (if not all) lathe tool blanks are High Speed Tool Steel. They are supplied hardened and tempered to the correct hardness. You should shape them using a bench grinder with a 60 grit aluminum oxide wheel. (this is a somewhat dangerous operation and you should use proper precautions, tool rest up close to wheel and EYE PROTECTION) Since the tool blank is already hardened, you need to keep the temperature of the blank low. Cool the blank in water. Try to keep the tool bit blank from changing color from it's bright polished steel color. (a little change doesn't seem to make a difference) Carbide tools are supplied already ground to the correct shape and do not need to be shaped. Home shop hobby machining like most of us are interested in, is best done with HSS (high speed steel) tool bits, shaped to the particular job. A properly ground tool bit is joy to use and the satisfaction that you ground it your self is a real plus! Leo (grind only the tool, not your fingers) 8-) ----------------------- Date: Thu, 01 Nov 2001 18:43:38 -0800 From: S1 Subject: Re: Heat Treatment Original Message - From: "Randy" To: >> I have to heat treat O1 steel ..I have no viable means that I know of >> Somehow I didn't think a couple of propanetorches would be enough >> I'll take any ideas .. Thomas Stubblefield wrote: > Randy, >If a propane torch isn't enough you might swap out your propane for mapp >gas. It burns hotter and may be enough for what you're working on. As for >the procedure on O1, someone else will have to take it from here. Tom If you have access to an Oxy-acetalene torch kit, you can swap out the Acetelene with Propane (use the tank from your BBQ grill) and it will be hot enough. Put a Rose Bud tip on the handle and it will be all set. Steel all heat treats the same: Get the piece glowing orange, quench it in either oil or water (depending tempering medium of the steel). Basically you're causing the atoms to rearrange themselves in the steel (making them denser), and then locking them in place by cooling material down very rapidly. Without the quenching medium, you will just anneal the steel and it will get a result opposite of what is desired. A friend of mine does blacksmithing and he uses a coal/coke fired, refractory lined forge for his work. That is optimal because it insures a much more evenly heated workpiece, but in a pinch an oxy-fuel torch will work. Gabe ------- Date: Tue, 04 Jun 2002 17:45:30 -0000 From: "jdmichael2001" Subject: Re: Water or oil or air hardning. In atlas_craftsman, "Harvey Noel" wrote: >> I am looking for drill rod to use on my atlas for components on a small engine I am building. Water hardened is the cheapest, oil hardened nest and air hardened by far the most expensive. What's the difference. Is air hardened at 4 times the price worth it? Harvey << Harvey: It usually depends mostly on the shape of the part, that is, the liklihood that it will warp or crack in heat treat. The quenching severity goes in the same order from water being most severe to air being the least. Long thin blade sections which must stay flat, or parts which have unavoidably sharp inside corners might require air hardening steel. Stubby, non critical parts like pivot pins, might be fine with water hardening. Oil-hard lets you hedge your bets at a moderate cost increase unless either warpage or absolute lowest cost are driving factors. The alloying elements in air hardening steel which give it its qualities often have a side benefit of slightly more wear resistance. However, if high abrasion resistance, impact resistance, heat tolerance, or corrosion resistance are large factors you can choose an alloy that excels in that environment. You also have the case hardening option which would give you a high surface hardness with a tougher or cheaper core. For instance, an 8620 steel is often recommended for gears to give a strong core, with a case hardening for surface wear resistance. Jan ------- Date: Thu, 05 Sep 2002 05:54:16 -0000 From: "k7jpn" Subject: Annealing Bolts I need some help with a weekend project. I have to machine a 3/8-24 bolt by removing about a 1/8 inch off the shaft (the bolt head will be cut-off before I start, as it will no longer be needed). I assume that I have to anneal the bolt before I start, but I do not have a clue how to do this. I have a 6inch Atlas, so there is not a lot of power to just plow through the thing. 8-) I do have an acetylene torch, so heat should not be a problem. There will be minimal loads on the bolt after I am done, so I will probably not worry about tempering it again, but it would be nice to know how to do it for future projects. Thanks in advance! john ------- Date: Thu, 5 Sep 2002 02:36:19 -0400 From: "MERT BAKER" Subject: Re: Annealing Bolts Start with a category 1 bolt, & you won't have to anneal anything. Even Category 5s can be turned fairly easily. If you gotta anneal, heat it cherry red & stick in dry sand or ashes to cool. Mert ------- Date: Thu, 05 Sep 2002 02:43:36 -0400 From: Stan Stocker Subject: Re: Annealing Bolts Hi John: Most bolts aren't particularly hard, even grade 8 stuff cuts pretty well. Grade 2 (normal OK hardware store stuff in most cases) cuts like most 1040 or 1018 steels. If the bolt is too hard to machine, you can probably draw the temper down without needing a lot of heat, around 500F and allowing to cool in still air gets most steels down to fairly soft state. Not as good as a dull red cooking with a slow cool in ashes, but usually sufficient. Better yet, keep the good bolts for where you need them and go grab a length of allthread if you can find it in NF thread, or some cheap 3/8 bolts to use for this application. Cheers, Stan ------- Date: Thu, 05 Sep 2002 06:59:17 -0000 From: "srediske11" Subject: Annealing One of the best(slowest) ways that I know of to anneal, if you don't have or want to deal with ash is to use vermiculite... insulates really well, so be carefull, I annealed a short steel bar and placed it in my vermiculite bucket and the next morning it was still hot enough to burn me! Ouch!x~xx#$% Samuel ------- Date: Thu, 5 Sep 2002 07:42:53 -0500 From: "jerdal" Subject: Re: Annealing > One of the best(slowest) ways that I know of to anneal, if you dont > have or want to deal with ash is to use vermiculite... insulates > really well, so be carefull, I annealed a short steel bar and placed > it in my vermiculite bucket and the next morning it was still hot > enough to burn me! Ouch!x~xx#$% Just as a point of information, I would recommend getting rid of any vermiculite you still have. Much of it has the worst form of asbestos in it, due to the source. One session of insulating the attic with the vermiculite insulation has apparently resulted in incurable lung cancer years later. This is in persons with no other elevated risk factors. Jerry ------- Date: Thu, 5 Sep 2002 09:24:35 -0400 From: Chabannes Rene N Contr ASC/YCD Subject: RE: Annealing I just looked at the EPA site on vermiculite. They greatly play down what has been in numerous othe sources. Given the current administra- tion's focus on such issues, that may be expected. Unfortunately, all politicians seem to have a price. The bad stuff comes from out west - Libby,Montana, in particular. If it comes from Georgia or I think Florida, not nearly as bad. There was a big scandal over this some time back where false reports on asbestos were made for years. The most real danger comes from frequent exposure - breathing the dust. BTW Vermiculite is in lots of stuff - most notably potting soil. Rene N. Chabannes (Titan) ASC/YC - Productions Operations C-17 SPO, WPAFB, OH 937-255-1042 (DSN 785-1042) -------- Date: Fri, 16 Aug 2002 08:18:11 -0700 From: "Dave Hylands" Subject: RE: Oil hardening > From: Daniel Munoz [mailto:dmunozx~xxvideotron.ca] > Sent: Friday, August 16, 2002 7:06 AM > To: sherlinex~xxyahoogroups.com > I want to make some punch from oil hardening rod. The punch > are intended > to cut discs and hexagons in soft material (styrene, maybe very thin > aluminium sheet) in miniature sizes (0.2" and smaller) and > need to keep a sharp edge. > I have at hand some 1/8" and 1/4" oil hardening rods (0-1 quality ?), > and a small butane torch. but I have no idea of what I need to do for > hardening the tip after I machined it to suit my need. Never done that > before. Simply heat to red it and quench it in oil ? > Can anyone give me some advices, what kind of oil I need, if > I could use water instead, the procedure to follow for hardening the > tip, or some basic links on the web ? Thank you for your help, Daniel. Hi Daniel, I've only done this once myself, but I'll speak up and somebody who knows better can correct me. First step is hardening. You heat it until it's red hot and quench it. I use a welder's magnet and heat the part until it loses it's ability to be attracted to a magnet. At that point, you've gone beyond the "critical" temperature. I find this a bit easier than trying to guage the various shades of red. Second step is tempering. For a punch, I've read that you want to temper to a light straw color, which means that the steel needs to be heated to about 465 degrees F. In order to see the "color" you need to have a shiny portion of the punch. You can expose a shiny portion with a piece of sandpaper or emery cloth. I would expose a bit lengthwide down the punch. Now start to apply heat away from the business end of the punch and you will eventually see colors starting to move towards the tip. When you see the light straw color reach the tip. quench again. You could also use a BBQ, a hot plate, or a regular oven to get the temperature of the metal to 465. You don't need to quench in this case, since as long as the temperature doesn't go above 465 it will be tempered correctly. When quenching, don't just dunk the piece and leave it in one place. Move it up and down slowly. Otherwise gases build up around the piece and make the quench not work as well. Here's a web page called "The Woodworkers guide to Tool Steel and Heat Treatment": , which I found to be quite useful. I used motor oil for quenching. Apparently you can use vegetable oil. Some people don't like the smell of motor oil and have use peanut oil. You can also purchase quenching oil from any good store that sells machining supplies. Dave Hylands Vancouver, BC, Canada http://www.davehylands.com/ ------- Date: Fri, 16 Aug 2002 11:17:10 -0400 From: RichD Subject: Re: Oil hardening Daniel: You only need to heat the tip end of the punch to a bright red (in a lighted area). Do this as quickly as possible to avoid thick scale formation. Quench straight down in any oil. Motor oil will do fine. For small items a wide mouth quart container full will be ok. When cool, clean the scale off the surface to bright. Reheat from the shank end watching the color change travel toward the tip. Just as the tip begins to go from a dark straw color to a light blue, quench again. It's now ready to use. A small butane torch may not have enough heat output for open air heating. The heat loss is enormous in air. A blanket of ceramic wool can be folded to make a muffle. Lay the tool inside and blow the flame thru. A propane torch would do better. Richd ------- Date: Wed, 04 Sep 2002 11:31:35 -0000 From: "mileagemayvary" Subject: Re: Heat treating help In sherline..., "smittys8002000" wrote: > I need to do some heat treating to some 4340, for some shafts thatI > make for my hobby. It has been a long time since I have done anything > Smitty Here is what I do for drill rod/silver steel/tool steel. For the bed I use coke (not the drink or the white stuff). It is processed coal that is used in boilers, and you used to be able to find it around industrial places. It looks like porous charcoal. Also it adds some carbon. Only need few handfuls. Had mine for 40 years. If you make the pieces of coke about 10mm - 30mm these can be packed around the item. It heats up very fast and retains the heat, and does not really burn away. Put this in a metal container. Put the item in the bed of coke so it is a bit more than 50% covered and play the torch on the resulting gap. Depending on the size of that shaft, propane may not be hot enough. I prefer Mapp gas also called Turbogas (lpg & acetylene). It burns at 2500C and is readily available and so are the torches at reasonable prices. I have 2 torches, one is self igniting. However one burns much hotter and nicer than the other although the burners appear to be identical. Also good for silver brazing. For quenching use ordinary clean engine oil from the car place. Put some in a food tin with a press on lid so you can store it, and it can be knocked over (it will be). The can needs to be much bigger than your metal piece to stop the oil overheating. You need to do the heating inside, but ventilated (I use a small fan to disperse any gases), so you can watch the color. However you must have the can of oil OUTSIDE because quenching will cause a lot of choking smoke and may be a fire risk. I heat until the metal is just a bit less yellow than the surrounding coke which will be very hot and yellow. Some people suggest rubbing the metal with ordinary soap before heating. When that goes black it is correct temperature for most metal You can also get rub on pencils for different temp indicators. Have tongs/pliers standing by. Run the metal out to the oil can and lower it in. Stand back! Be careful of burning oil splashes. Take it out. Remove any oil. Test with a file for hardness. To temper you then put it back in the coke. Heat until it just shows the slightest color change "blush", then allow to cool slowly OR.. Put in the standard oven with the Sunday roast. Cook at 200c for just over an hour. Rob ------- Date: Tue, 10 Dec 2002 10:26:27 -0800 From: "Mark Beyer" Subject: Re: ISO: Metal crafter to make guitar bridge steel rollers [SHERLINE GROUP] Bruce: Thank you for the question. Cryogenic processing has been around since shortly before W.W.II. Unfortunately, due to control problems it largely disappeared until computers could take over the accurate control needed for the nitrogen feed. Cryo'ing is a process of material improvement used to remove latent stresses from metals and some limited other materials. Depending on the materials and wear inducing applications it increases total material structure and surface durability up to 800%. In music it removes the sour notes from the locked in metal stresses. On sporting goods like golf clubs and softball bats it increases "pop" for more power and distance. Firearms and high tech products also benefit through improved accuracy and tolerances. There is highly technical aspects of what part of the material changes due to the process involving carbides and grain structure. Uniformly, stress reduction is the universal benefit in all materials which we currently process. There are good things and bad things about cryo'ing. The good thing is it's cheap. Nitrogen constitutes 73% of the air we breath and when they liquefy gases Nitrogen is the cheapest and most abundant gas to liquefy. Using it as a refrigerant is cheap and accurate now. The bad thing is, it's almost impossible to tell if a cryo process has been accomplished on a material since there is no residue or obvious and observable change. So, unscrupulous processors will either squirt or dip and ship, meaning the material is processed too fast and is actually harmed instead of improved or they don't even process at all but still charge for it. So, those of us with scruples in the business suffer from the inconsistency of others. The process is a timed cooling from room temperature to -300 degrees F at no more than a single degree per minute rate. A 24 hour or greater soak at -300 degrees F and then a warming back to room temperature again at one degree per minute. It really is the logical conclusion to the forging process as the benefits of tempering don't end until the material reaches absolute zero. Liquid Nitrogen temperatures being the closest economical to absolute zero we can now reach. I hope I answered your question fully enough. If you want I can answer further some specifics on the effects and benefits. If you chose a company to have your processing done by, get to know them enough to trust they won't cheat you on it. I would rather see a satisfied customer for any good cryogenic company out there than hear perpetually about how the process didn't work for someone due to poor processing methods the few bad apples out there use. The hobbyist probably won't see too much in the way of cryo treated materials and tools for now. Softball bats, golf clubs, and circular saw blades being the exceptions. My goal is for everything to be treated which will benefit from this process so it becomes transparent to society. That's why I always look for converts to my belief. Mark Beyer ONECRYO ------- Date: Sun, 26 Jan 2003 23:29:25 EST From: LouD31M066x~xxaol.com Subject: Re: source for mt1 & mt2... [THAT ARE "HEAT TREATED"] Heat treated means that a steel with a suitable carbon content was heated to a temperature high enough and long enough to create form a form of carbon crystal ( little hazy on names or exact science but bear with me) and then cooled quickly below the transition temperature so these high temperature forms would exist in the steel at normal temperatures. This is full hard in shop I worked in above 500 Brinnell (measure of hardness) and also brittle (not exactly like glass) Now understand the heat treating process was used in the place I worked to not only harden but also to increase yield strength from about 30,000 # sq inch to around 100,000 # sq inch. To make suitable balance between strength and brittleness steel is then put in a lower temperature furnace to reduce hardness by allowing some transformation of high temperature form of carbon to return to a normal temperature form of carbon crystal. Parts then would measure desired level of hardness and not be so brittle. Major customers was Cat, P & H Crane, so product had to be strong but not subject to brittle fracture. Case hardening is a different process where a steel with a low carbon content is given a hard case or shell by heating in presence of a carbon or carbon compound so that steel at surface accepts carbon and when cooled has a hard surface and a soft core. The element iron with little or no carbon is called iron. The element iron with a great deal of carbon is called iron. The element iron with an intermediate content of carbon is called steel. The level of carbon in iron and the form in which it exists (along with larger or smaller amounts of alloy or impurity) vary the qualities and usefullness of steel and account for why some steel is better or worse for a particular purpose. People who understand the whys and hows of all this are usually graduate metalurgists and or chemists. Back to your question sticking a piece of steel in a fire and then a bucket of water is heat treating,but, there is a whole science behind it. Louis ------- Date: Mon, 31 Mar 2003 23:57:18 -0000 From: "Thomas " Subject: Kasenit? I'm in the middle of making a toolpost mounted knurler out of low- carbon ground flat stock, and am wondering if I should harden it with something like Kasenit (especially in the holes that the pivot bolts will pass through). Do you think hardening something like this would be overkill? Thomas ------- Date: Tue, 01 Apr 2003 04:05:52 -0000 From: "Robin S." Subject: Re: Kasenit? I think it would be fairly useless. You want toughness, not hardness. Making them out of a medium/high carbon steel would have been a smarter idea. 4140 is a good choice. Heat to 1600º (red hot) and quench in oil. Put it in your oven as hot as it will get for an hour or two and you've got some tough stuff. Mind you, I don think it would hurt to case-harden the part, but I think it would be a lot of work compared to the benefit. Regards, Robin ------- Date: Tue, 1 Apr 2003 09:40:20 -0800 From: "Nicholas Carter and Felice Luftschein" Subject: Re: Kasenit? I made mine out of CRS, I haven't noticed a need to harden. I think that it wouldn't hurt though. See our web pages http://www.cartertools.com/nfhome.html ------- Date: Tue, 01 Apr 2003 17:06:58 -0500 From: Tom Wightman Subject: Re: Kasenit? Thomas The knurling tool I made, the body was from 1020 cold rolled. The pins on which the knurls ran (they are fixed in the body but the knurls rotate on the pins) were unhardened drill rod. The pins wore quite quickly, but everything else has been fine. I replaced the pins with an identical set, but hardened them and tempered at about 500F (domestic oven) - no more problems so far. Regards Tom W. ------- Date: Tue, 01 Apr 2003 23:42:03 -0000 From: "Thomas " Subject: Re: Kasenit? Thanks all for the good advice. I think I'll skip the hardening part, and if it wears out, I'll just have to make another one even better ;) Thomas ------- Date: Sun, 13 Apr 2003 18:40:36 -0400 From: "Thomas R. Bank" Subject: Heat Treating Tools I was watching The Woodwright's Shop on PBS last night. They were visiting the guys at Williamsburg VA, who had a demonstration of old fashioned technique that was quite interesting. They made a chisel and then heat treated it. Standard practice, except that they welded a piece of steel to an iron blank to get a good cutting edge while using cheaper iron for the bulk of the tool, then heat it in the forge (my grandpa had one of them in his garage - boy would I ever like to have one like it) and quench it, followed by the tempering process, -- but that's where the process got neat. Instead of sticking the cleaned-off metal (he cleaned it with a brick instead of a file or grinding wheel) back in the fire to warm it up, the smith's helper brought over a piece of iron about 4" X 12" X 1" thick that was close to white hot and laid it on the bricks. The smith then stroked the chisel back and forth on the hot bar, heating it evenly until the color he wanted - the purple after the straw and orange in this case - started to show. Surprisingly, the color was very evident even on television. Using a torch, I have had hard times at time catching the color when tempering drill rod, and in the little gas forges we had back in Junior High it was really difficult. Those guys with their 200 year old techniques made it a piece of cake. Regards, Tom Bank ------- Subject: Re:making a scratch awl oldtools digest From: "John Sawchak" Date: Sat, 13 Dec 2003 23:53:59 -0600 I made an extended point for my spring-powered centerpunch once. I used a solid steel pushrod from a high winding (gear-driven timing chain) v-6 ford motor. Actually being as the motor went shot I turned a great number of these pushrods into useful little tools. Some are pin punches, some hole cutters, basically a little bit of everything. I annealed the steel first (heating til it glows and then cooling it slowly in whatever insulating material you have handy) so I could work it easily. Then I ground it to whatever I wanted. In this case I ground it by chucking it in a drill and turning it on my grinding wheel until it was what I had in mind. I then heated the end cherry red and plunged it into tranny fluid. This hardened it. I didn't bother tempering it. It has held up just great. I used the same technique using an old file to make a marking knife. ------- Subject: Re: Making tools, files, scrapers and stuff oldtools digest From: "Todd Hughes" Date: Sun, 21 Dec 2003 22:28:39 -0500 Bruce asked....,>, I saw a pretty nifty "user made" > wooden router plane that used a file for the blade.... > My question has to do with using an old > file for something like this. In this case the end of the file had been > bent a little bit and then was ground and sharpened. I am basically > metalurgically indept, so if one were to attempt to do something like > this, would one have to do anything special to the file? Does it > need to be tempered on anything? Seems like a file should be hard > enough (at least for a router plane). What about bending it? Could > that be done cold? A File can not be bent cold as it is very hard and brittle, will snap right away, this is because of the way it is tempered .The File has to be heated up to at least a red heat and bent hot then annealed by letting it cool slowly in some wood ash.After cool it should be soft and then you can file or grind it.After shaped heat it up to a red heat and harden in some oil and then temper it at about 350 deg. ...I have made many hundreds of Knives out of Files as well as using them for the bits in Axes and making Springs etc., really ain't much to it... Todd ------- Subject: Re: Oil vs water hardening oldtools digest From: "Phil and Debbie Koontz" Date: Mon, 22 Dec 2003 09:59:46 -0900 Hi Galoots-- This is one of those situations where simple answers almost always lead to problems. I'm reminded of a few years ago, when I took a couple forges along on a Boy Scout campout, and we did some smithing. It seems to be a natural law that when the boys get to a certain age, the only thing they want to make is knives, or even better, swords. And I always tell them to forget it. It's easy to do a bad job of making knives, not so easy to do even a bad job of making a sword, but doing a good job of knifemaking is something that you have to work at. Care about. Study. Spend some time on the subject. To tell you the truth, it's not something I'm real good at anyway. I know just enough to really appreciate my ignorance. So, where to start. Quenching hot carbon steel. Rapid cooling forms crystals. Iron crystals are cubic. Carbon impurities get trapped in the cubic structure and put it under stress. Think of a wooden box with an inflatable ball inside. When the crystals suddenly form and shrink, they trap the carbon inside, like a ball that's too big for the box. That stress gives the steel its hardness, but it can be too much stress, which is the reason the steel tends to warp, crack, or simply to be too hard. Tempering lets the crystals relax just a little bit, so some of the carbon can migrate to a little lower stress position. The main benefit of tempering is to increase toughness, or reduce brittleness. The reduced hardness is the result of more toughness. (I'm simplifying this subject radically, partly because I don't understand it very well. There are actually at least four or five crystal species involved, not just one or two...) Water hardening steel (and there aren't many of them left anymore W1, W2, and 1095 are about it--and they are hard to find) needs to cool very quickly to develop it's full hardness. This rapid cooling works best on thin parts, like knife edges and springs. For thick parts, the hardness doesn't penetrate, because the steel holds heat too long. Old time smiths tended to use saturated salt water as a quench to get around this problem, because it raises the boiling point and increases the cooling rate. We're talking about fractions of a second here... The benefit of oil and air hardening steel is that you can get more penetration and harden thicker pieces of steel. Rev Ron has mentioned this IIRC--W1 plane irons tend to have a soft core that eventually emerges as they wear down. It turns out that a couple of additives make the steel gain its full hardness even if it cools slowly. I think that they are mainly molybdenum and, to a lesser extent, chromium. Look it up, if you really want to know. Oil hardening steel (O1 and others) harden at a moderate cooling rate, so that the core of the part gets hardened as much as the outside. Air hardening steel allows an even slower quench. That said, there is some cross over. See this web page for examples. http://www.dfoggknives.com/waterhardening.htm And here's a good source for steel properties and buying tool steel http://www.crucibleservice.com/eselector/selectorindex/selec torindextitle.html The general rule for an amateur shop is try oil quenching first. It probably won't hurt the steel. If that doesn't do it, then try a water quench. If that still doesn't do it, maybe try saltwater or superquench. (What's superquench? A home recipe for hardening low carbon steel; it's on the net somewhere--) One of the problems with this rule is that people tend to go from the hardening step right back to another hardening step. There is a big problem with that too. Crystal growth. I really don't want to get into this subject too much, but high temperatures make the steel crystals grow, and that's bad. The smaller they are, the better. Another good rule is to find one kind of steel that you can handle predictably, and stick with it. I don'tknow anyone that actually follows that one, though. There are two ways to make the crystals smaller; forging and annealing. Forging means that you have to actually work the steel, and knead those crystals out--break them down with your hammer. Some knifemakers will tell you that you have to put the same number of hammer blows on both sides of a knife blade, in a symmetrical pattern, or the steel will warp. Crystal growth is the reason. Annealing is slow cooling from the critical temp of the steel. The slower the better. Burying the red hot steel in ashes overnight is the traditional technique. It removes the crystal structure altogether. So the rule is--anneal, then harden, then temper. If you don't like the result, repeat the process from step 1. And there's a problem with that. Every time you heat the steel, you are potentially burning off some of the carbon, which means that the surface of the steel won't gain its full hardness. And of course, there is always the surface scale loss and the possibility that you will burn the stuff up altogether... So there you go. All I know about the subject. Phil Koontz Galena, AK ------- Subject: Re: Tempering [Oldtools group] From: Jim Wallbridge Date: Tue, 02 Mar 2004 10:07:15 -0700 On Tuesday, March 2, 2004, at 09:08 AM, Mike Duchaj wrote: > Question for the tool makers and metal heads, > I am making marking knives. I used file stock for blades. It was > annealed and shaped, then rehardened. Now I have to temper it. I will > use the oven method. > Phil said to temper to 425 for plane blades. Is that OK for marking > knives too? Since temperature is controlled in the oven, do I need to > quench after heating, or just let it cool slowly? I know I would need > to quench if I used my forge to heat the tang, to prevent over-heating. Mike & Galoots Yes 425 F would be Ok. I realize that the following may be controversial. In general for high carbon (~1.3%) tool steel, which good files are made from, the temperature to be used for tempering depends on the hardness desires of the user. For the highest hardness (which I use for chisel and planes used for finishing) tempering at 275 - 300 F for one hour is about the lowest that should be considered. These is data to indicate that torsional toughness is at a maximum in this temperature range but it is still relatively brittle but does yield a beautiful long last cutting edge but it must be handled with care. I would consider this too hard for a knife except for one with only a very specialized use. Hardness goes down from there as the temperature goes up but I would suggest not using temperatures between about 425 and 525 because of potential brittleness in this range. At temperatures above this consideration should be given to using a lower carbon steel as it will provide a better mix of properties I would suggest that one hour be used for tempering but there is no harm in longer times within reason. Very short times as used in running the temper methods are not as effective and somewhat higher temperatures (+25 F) result in similar hardness As to quenching after tempering: certain alloys, particularly those containing Cr, P, As and others, can be brittle if not quenched but for most alloys it does not matter. I tend to quench if convent. jim (James ME Wallbridge P. Eng (retired).) Libertarian, Metallurgist, Wood & Metal Worker, Fly Fisher, Resident of Calgary, Canada's new head office location of choice. Permission is hereby given to use any or all information herein, as an attributed quote, unless the body of the message states otherwise. ------- Date: Mon, 21 Jun 2004 13:21:31 -0700 From: William Abernathy Subject: Re: Heat treating oven Ron Gerlach wrote: > Has anyone out there used a ceramic kiln for heat treating? They > seem like natural choices and the small ones are fairly common and > cheap. They all seem to be able to heat well past the 1450F > temperature needed for hardening. It would be a fairly simple > matter to add a thermocouple and controller to get programmable > temperature control. My neighbor has a kiln (she's a ceramist) and when I asked if I could use it for heat-treating small parts, she declined, because opening the lid on a running electric kiln to remove a part thermal-shocks the heating elements (so she claims, at least) and wears them out. Dunno if it's true, but (A) she believes it, which put an end to that discussion, and (B) I went and built a small kiln out of firebrick and a Reil propane burner instead, and that's worked fine for heat-treating small parts for me. Obviously, you have more sophisticated requirements than are satisfied with the "shoot it with fire 'til it glows for a while" technique which has sufficed for my crude implements. Inquire about thermal shock before jumping in and buying an electric kiln. I may well be blowing your way the same smoke that was blown up my bum. William A. ------- Date: Mon, 21 Jun 2004 21:40:56 +0100 From: "Brian Squibb" Subject: Re: Heat treating oven I guess a kiln would be excellent at case hardening when the oven could be left to cool down.I have a friend who uses a kiln for heat treating without problems. Brian ------- Date: Mon, 21 Jun 2004 16:57:13 -0400 From: "mertbaker" Subject: Re: Heat treating oven Small parts (firing pins, screwdrivers) can be heat treated with a propane torch. Larger ones on the gas burners on the stove. Mert ------- Date: Mon, 21 Jun 2004 22:57:55 +0200 From: "J.C. Gerber" Subject: Re: Heat treating oven It is true that a ceramic oven could be killed this way and it is true too what Brian says. It just depends how fast you can take the piece out of it and close the door. Then the thermal shock is not that bad. Jean-Claude, Switzerland www.homestead.com/turnandmill ------- Date: Mon, 21 Jun 2004 15:28:04 -0700 From: Wally Merrin Subject: Re: Heat treating oven > Has anyone out there used a ceramic kiln for heat treating? They seem > like natural choices and the small ones are fairly common and cheap. Paragon makes ceramic kilns and also makes electric heat treating ovens and a line of knifemaker's ovens. http://www.paragonweb.com/index.cfm These ovens don't seem to be bothered too much by the thermal shock of opening and closing the door. I have used the knifemaker's ovens (I would love to own one) and they are great. They aren't cheap but they have digital controls and work nicely The big disadvantage of ceramic kilns is many of them are top loading, which means for heat treating you are trying to get your parts out by reaching down into a very hot hole and then quickly getting it into the quench. The heat treating ovens are front loading so you can open the door and reach in with tongs without broiling your hands and arms. Wally ------- Date: Mon, 21 Jun 2004 20:18:07 -0500 From: Bill Aycock Subject: Re: Heat treating oven I have used several types and brands of ceramic and enameling kilns, and have heat-treated and tempered steel in them. Unless your size needs are large, I think an enameling kiln is the best bet. Most are designed to be opened repeatedly, and have doors that swing open, for horizontal insertion. They don't get as hot as ceramic kilns, but 1600 F , steady state is normal. Many ceramic shops also have access to enameling kilns, or you can try Rio Grande, in New Mexico. Rio Grande also handles controllers, usually used for glass tempering. Bill Aycock - W4BSG Woodville, Alabama ------- Subject: Re: Wanted - Blade hardening for Dummies From: bugbear Date: Mon, 28 Jun 2004 09:03:57 +0100 Derek Cohen wrote: > Esteemed Galoots > I recently acquired a 3/8" corner chisel, the steel of which requires hardening. At present the blade just burrs (like a scraper) when I sharpen it (on a diamond stone) and the edges just folded over when I attempted to use it on one occasion. I was told that it was New Old Stock so I must assume that the steel is soft (VERY soft!). In appearance it resembles a steel bar with a machined out corner section. I think Lie Nielson made some like this some years ago (but this certainly ain't no LN!). < IIRC corner chisels are made soft to ease the (very difficult) process of sharpening the damn things. BugBear ------- Subject: re: Wanted - Hardening Steel For Dummies From: "Ron Hock" Date: Tue, 29 Jun 2004 15:39:41 -0000 Go here: http://www.hocktools.com/diyht.htm Good luck, Ron ------- Subject: RE: Wanted - Hardening Steel For Dummies From: "Thomas R. Bruce" Date: Tue, 29 Jun 2004 15:01:02 -0400 Ron and all: Ron's the master, and no doubt about it, but I can add a couple of tricks I've picked up from the knife-making crowd: 1) Heat-treating with a propane or MAPP torch is a lot easier if you add five or six firebricks to the process; you can get 'em from a local masonry or fireplace shop. I stack them up crosswise to form a sort of firebrick tunnel with a 1-2" square opening through which the torch flame is directed. Concentrates the heat *much* better than just waving a torch around in the air, and makes it feasible to work with larger pieces. Next time I think I'll try rubbing some charcoal around on the inside first, just to see what an oxygen slut will do, if offered the right inducement. 2) Olive oil works too, and is easier to get around here, and also will not flash. 3) Any oven is an accurate oven if you use an oven thermometer (grin). 4) A pair of the needle-nose type vice-grips makes a very good work holder when working with the "firebrick tunnel" technique above. 5) For knives, you can get tricky with hardening by quenching cutting-edge first, leaving a softer and hence more robust spine. Probably not worthwhile with a plane blade, though. I've only worked with O-1, howsomever. t ------- Subject: RE: Wanted - Hardening Steel For Dummies From: "Jeff Gorman" Date: Wed, 30 Jun 2004 07:22:09 +0100 Even better would be refractory insulating bricks, items that are used for lining potters kilns. These are lightweight, crumbly bricks. I've seen one face heated red hot and then the brick picked up, held by the opposite face. Jeff Gorman, West Yorkshire, UK http://www.amgron.clara.net ------- Subject: RE: Wanted - Hardening Steel For Dummies From: "Blake Ashley" Date: Wed, 30 Jun 2004 07:48:27 -0700 You can buy the refractory insulating bricks Jeff describes at stores that sell jewelry making supplies. They are soft enough to allow holding small parts by sticking them into the brick surface. ------- Date: Mon, 21 Feb 2005 07:26:51 -0000 From: "mileagemayvary" Subject: Re: Heat Treating Gear Hob [sherline group] "Devin Cox" wrote: > I just finished a gear hob and want to heat treat it. I know I > should heat the hob to cherry red and then quench in cold water. But > then the video "making gears the easy way" says you need to polish > and then temper to a straw color. The polishing and tempering was > not shown in the video. Can someone please explain this process? My method is: Get a small metal container filled with coke. Not the powder, not the drink, but the carbon stuff made from coal you sometimes see laying around in those disused factories :( If you cannot find some then use charcoal. Bury the item in the coke with a window hole. Heat the item and surrounding coke with MAPP or propane to cherry red. Color depends on the alloy. The idea is to move carbon from the coke across to the item. Dump item into a can of engine oil. Do this outside (before it can cool) as it produces acrid smoke and a fire risk. Clean up item and rebury it in the coke. Heat to straw color, cover with coke and allow to cool for 1/2 hour. *Do not quench it*. Try the routine on a small piece of the metal. If you get it right then a file will not touch it, but the metal will be very tough. Incorrect tempering and it will shatter (and appear quite crystalline at the break) in use due to being brittle. Rob ------- Date: Mon, 21 Feb 2005 03:07:25 -0500 From: "Jerry G" Subject: Re: Re: Heat Treating Gear Hob Rob, have you ever tried "Kasenit"? You are describing case hardening anyway... By letting it cool for 1/2 hour, (even packed in coke) you are actually "air quenching" it, in a way... Jerry G (Glickstein) ------- Date: Mon, 21 Feb 2005 08:07:38 EST From: Holyelvisx~xxaol.com Subject: Re: Heat Treating Gear Hob Jerry, I planned on using my oxy/acet torch to heat the hob, is this too much? I have a small propane torch as well but thought it might not get hot enough. The hob is made from tool steel. Devin ------- Date: Mon, 21 Feb 2005 08:26:15 -0500 From: "Jerry G" Subject: Re: Heat Treating Gear Hob Devin, the Oxy/acet is fine, but use a slight excess of the acet to minimize the oxidation. that is why the stainless steel bags are cool... there should be a nice cone of blue at the tip and don't stay in one place, try to heat up the whole piece uniformly.. what kind of tool steel? Regards, Jerry G (Glickstein) ------- Jerry, I am not sure what kind of tool steel it is. I just had some laying around from a project last year. Devin ------- Devin, the type is important because you would then know if it is Oil, Water, or Air hardening.... A neutral ( about one to one mixture of the two gases) to carburizing flame (slightly excess acetylene ) is preferable... Regards, Jerry G (Glickstein) P.S. Do you know how to do a spark test on the steel? ------- Jerry, I have not heard of a spark test. I just pulled the scrap out of my bin. I hope I can use this piece because I have already cut it. (c: Devin ------- Date: Mon, 21 Feb 2005 09:06:02 -0800 From: "Marcus and Eva" Subject: Re: Re: Heat Treating Gear Hob Hi Devin: Take a file, (an old thrasher that you don't need anymore) and touch it to a spinning grinding wheel. The sparks will come off very bright and sparkly...yellower than a kid's birthday sparkler, but quite similar otherwise. Now take a HSS lathe toolbit and touch it to the wheel. You'll get globular red little sparks that look dull and uninteresting by comparison. The sparkliness and yellowness of the spark is an indicator of the amount of Carbon in the steel, and the globularity and redness is an indicator of the amount of Chromium and/or Vanadium in the steel. Bright yellow sparky steel has lots of carbon...GOOD for home heat treat. Dull globular red sparky steel won't torch harden very consistently... POOR for home heat treat. All high carbon steels can be water quenched. Many can be oil quenched. A very few can be air quenched. Water quench introduces high stresses in the cooling steel...high hardness and high risk of cracking and warping. Oil quench is moderate in both. Air quench requires steels that will hold their Martensitic crystalline structure reasonably well through a slow cooling cycle...this takes special alloying to produce carbides in the microstructure. (The Martensitic structure is what makes it hard.) Impossible to control consistently without a heat treat furnace, because controlled precipitation of the carbides takes the right kind of temperature rise, hold and descent. My advice to you is to do the spark test on a scrap. Then try to harden the scrap with a torch and an oil quench. If it doesn't get hard, try a water quench. If it still doesn't get hard...you've got either an air hardening toolsteel, or a low carbon steel that will need to be case hardened to salvage the job. Almost every hobbyist who has "Mystery steel" in their scrap box that they "know is toolsteel" is talking about either O-1 or W-1. Both are high carbon steels that can be torch hardened. That's why you do the oil hardening test first...if it works, it's very likely O-1. (That would be very desirable because it won't warp as bad in the quench!!!) HTH. Cheers Marcus -------- Date: Mon, 21 Feb 2005 12:30:09 -0500 From: "Jerry G" Subject: Re: Re: Heat Treating Gear Hob So, Devin, Heed Marcus's words.... My colleague in crime has beat me to it....:) Regards, Jerry G (Glickstein) ------- Date: Sun, 29 Jan 2006 06:45:10 -0500 From: "L.A. Root" Subject: [OldTools] Annealing steel I wanted to make a striking knife and, not having an easy source for small pieces of steel, tried to anneal a small file. I placed it in my wood burning stove on hot coals for about 15 min.; when removed, it was a dull red. I promptly placed it, still red, in a can of wood ash until the next morning when it and the surrounding ash were still too hot to touch. The file was black when I removed it and placed it on the stove's steel lip to cool. When I file a soft steel, such as a common bolt, the file cuts it easily and quickly. A file will now cut the treated file, but it cuts slowly leaving a near polish. It is still, to my inexperienced hand, hard. When I grind it, it cuts as slowly as a chisel. Do I need to get it hotter; leave it at temperature longer; cool it differently? Or is this just a harder alloy even when annealed? Thanks for any advice you can offer. Very respectfully, Larry Root ------- Date: Sun, 29 Jan 2006 08:14:29 -0800 From: scott grandstaff Subject: Re: [OldTools] Annealing steel > Do I need to get it hotter; yup, bright cherry > leave it at temperature longer; yup a little longer can't hurt > cool it differently? No, that part is fine. Personally I put them in at bedtime as the last good coals are burning. Right in front of the air draft where it'll burn hottest and fastest. Drag some coals over for a bed. Pile with more live coals so as not to expose too much steel to the air. Hit the sack. It's done in the morning. yours, Scott Scott Grandstaff, Box 409, Happy Camp, CA 96039 Tools:http://users.snowcrest.net/kitty/scott/scotts/tools/tools.html PageWorks:http://www.snowcrest.net/kitty/hpages/ ------- Date: Mon, 30 Jan 2006 05:46:23 -0500 From: "L.A. Root" Subject: Re: [OldTools] Annealing steel Thanks for all your suggestions! I tried again last night getting it to a bright red-yellow, put it in the ask can overnight, and, this morning, it cuts easily. I now have a steel blank to abuse. But now I'm confused (my daughters might suggest that's not unusual): If I can temper the hardened steel at 350-400 and ruin it at 600 (or by careless grinding), why does it need to get that hot to soften it? What happens between 600 and what ever temperature it reached on the second try? Is there a continuum between room temp and that non-magnetic temperature that, at that boundary temp, suddenly changes? Is the ruining by grinding just moving to a less hard, but still hard spot on that continuum? When it's time to harden, how long do you have after you take the steel from the fire -- how quickly will it cool down? I don't want to oil soak it inside the house, and it will take 30 seconds or so to get outside. Is it worth an ash bucket for that length of time? Again, thanks for any further suggestions you can offer. ------- Date: Mon, 30 Jan 2006 10:18:10 -0500 From: "Seaman, Andrew K. (Andy)" Subject: [OldTools] Re: Annealing steel Larry's confused about heat treating steel: >Is there a continuum between room temp and that non-magnetic >temperature that, at that boundary temp, suddenly changes? The simple answer here is yes. Steel has phases, many many phases that can be obtained by different heating and cooling schedules. Check out this link: http://www.threeplanes.net/toolsteel.html Read the section entitled, "What Happens During Heat Treating of Tool Steel?" I think this will answer all of your questions if you read it a few times. There are several other phases of steel that are not listed in this phased diagram. Bainite (not mentioned in link) is ideal for some bearing steels that I work with. To answer your ultimate question Larry, >When it's time to harden, how long do you have after you take >the steel from the fire -- how quickly will it cool down? Not long. One, two seconds maybe. Putting your steel in ash to transport it outside to quench it will cool it too much. This is a game of speed. Pull your steel from the fire and thrust it in the oil as quick as you can. Otherwise, you'll never get the steel as hard as it can be. You might consider building your fire outside if quenching inside is not an option. Good luck! Andy ------- Date: Mon, 30 Jan 2006 10:37:15 -0800 From: Ron Hock Subject: Re: [OldTools] Annealing steel > Is there a continuum between room temp and that non-magnetic > temperature that, at that boundary temp, suddenly changes? Yes. The change at the high temp where it becomes non-magnetic is a phase change. The ferrite changes to austenite which is a completely new configuration of the iron atoms. The crystal structure changes from a "body-centered cubic structure" to a "face-centered cubic structure". When this happens, the carbon is free to migrate as if in solution and it finds new places to reside. When quenched from this temp, the austenite changes to martensite, a smaller, hard, wear resistant structure, and traps the carbon creating a highly stressed but very hard matrix. Subsequent tempering reduces stresses and "softens" the steel --up to a point. For full annealing, you need to reach that critical temperature and let it cool very slowly (as you've apparently done.) Be aware of the de-carburized skin that you've created with all this heating in air. When the steel is at the high temperature the carbon atoms are moving freely about and when one of them hits the surface it runs off with the first oxygen slut it bumps into (they're so seductive). Gone forever. So diy heat treating usually creates an unhardenable layer on the steel. Be prepared to grind that layer off, down to the good stuff, after tempering. > Is the ruining by grinding just moving to a less hard, but > still hard spot on that continuum? Yes. > When it's time to harden, how long do you have after you take the steel > from the fire -- how quickly will it cool down? I don't want to oil > soak it inside the house, and it will take 30 seconds or so to get > outside. Is it worth an ash bucket for that length of time? Unless you really *want* the divorce (and the insurance claim for the total loss), do this outside. Wear gloves that will resist fire, face/eye protection and keep a fire extinguisher handy. Move quickly from the heat to the quench (you really don't want to be running around with a piece of glowy metal). I do the heat-treat demo in my (very small) shop for groups of woodworkers from time to time. For a small blank of O1 (3/32 x 3/8 x 7") I use a quart paint can about 2/3 full of peanut oil (high flash point, smells nice when smoking) for the quench "tank". And I always enlist two visitors to be 1. the magnet holder, 2. the fire-extinguisher bearer (CO2 -- the powders are too messy). I just figure: small, cluttered shop, crowded with people, one exit, open flame, etc. Just wouldn't do to immolate potential customers. Good luck. Be careful. And you may want to check: http://www.hocktools.com/diyht.htm for some more tips. The Rev. Ron Hock HOCK TOOLS http://www.hocktools.com 16650 Mitchell Creek Dr Fort Bragg, CA 95437 (707) 964-2782 fax (707) 964-7816 ------- Date: Mon, 30 Jan 2006 10:57:49 -0900 From: "Phil and Debbie Koontz" Subject: Re: [OldTools] Annealing steel The Rev Dr. Ron straightens out our heat treating thread again-- >For a small blank of O1 (3/32 x 3/8 x 7") I use a quart paint can >about 2/3 full of peanut oil (high flash point, smells nice when >smoking) for the quench "tank". I just wanted to add that I think I've found a really good quench tank. It's an old 30 caliber ammo box. Just the right size and shape for small blades, fireproof, airtight, cheap, easy to handle, doesn't spill, and mice can't get in it. Mine is full of corn oil because peanut oil is pricey and hard to find around here. It works fine, but I find that the french fries get sort of funny tasting after you use it for heat treating a few times. PK It warmed up to -40 today in Galena. ------- Date: Mon, 30 Jan 2006 17:49:38 -0500 From: "L.A. Root" Subject: Re: [OldTools] Annealing steel Andy, Jim, Ron, and Phil, thanks for your helpful replies. Outdoors it is -- even if the oil didn't ignite, I love life too much to think of what my wife would do to me if I broke a quart of oil in the family room. Andy and Ron -- thanks for the site URLs. They were interesting and helpful. http://www.threeplanes.net/toolsteel.html http://www.hocktools.com/diyht.htm Ron -- thanks for the surface carbon tip. In addition to grinding the exposed surface off, it tells me that there is a down side to keeping it in the fire longer than necessary. Very respectfully, Larry ------- Date: Wed, 01 Feb 2006 16:06:23 -0000 From: "amsvette" Subject: A wee bit off topic - flame hardening of steel [atlas_craftsman] I recently had a need for some specialty pliers. In my line of work, copier repar, I come accross stripped screws. I had a pair of gasline pliers, which are similar to linesman pliers but have a cutout on the nose of the pliers for gripping small round objects (such as screws, etc). Long story short, Crescent discontinued them when I really needed a pair. Ebay to the rescue. I bought a pair of old J.P. Danielson gasline pliers. It's old and has definitely seen better days. After a quick de-rusting sesion I noticed the jaws are very soft and easily marked. Decided to try my hand at flame hardening and tempering. Based on what I read on the internet, I heated the jaws glowing red with my MAP gas torch, and quenched them in water. Then I tempered them by heating them gradually until the metal turned a blue/brown color and then requenched it. Now my question is (finally!) how do I know if I was successful? I was able to grip the screwhead I was tring to remove, but it still looks like I deformed the teeth on the pliers a bit. Any suggestions? Or do I have to live with the fact I'm trying to use a really old pair of pliers? Sorry for being so long winded. Thanks, Adam ------- Date: Wed, 1 Feb 2006 11:41:49 -0500 From: "Kirk Scammon" Subject: Re: A wee bit off topic - flame hardening of steel Adam: You should check to see if the pliers hardened after the first quench with a file. If they don't harden, the steel does not have enough carbon. You can buy some case hardening compound ( Kasenit ) that will allow you to form a case hardened layer on the steel. Brownells or McMaster Carr both carry it. Kirk ------- Date: Wed, 01 Feb 2006 11:31:45 -0500 From: "mertbaker" Subject: Re: A wee bit off topic - flame hardening of steel Those pliers may not have been made of tool (high carbon) steel. If they were not, they won't harden by that method. If they were, tempering at blue may have gotten 'em too soft. To find out if they were tool steel, use the grinder test. Take an old file, and grind a bit off the end. Note the sparks. Lots of "stars" indicate high carbon content. Try the same test with a common nail note: no stars. Low carbon. Now try the pliers, grinding a bit on the inside of the end of one handle. Tool steel? If so, heat the nose red hot & quench in oil. Try the hardness with a file. If the file will not cut the pliers, set 'em in the toaster oven at 425 for 20 min or so. If the file WILL cut the nose, reheat & quench in water. Try the file. Won't cut? temper at 425° as above. Not tool steel? Heat red hot & stir 'em around in a can of Kasenit (TM) from the hardware store. Reheat & quench in water. Now the surface will be hard, but the rest of the tool will be soft & tough. Mert MertBakerx~xxverizon.net ------- Date: Wed, 1 Feb 2006 21:47:45 EST From: jmartin957x~xxaol.com Subject: Re: A wee bit off topic - flame hardening of steel Mert is right on target. I'd add only a couple of things. If they were soft to start with, they probably weren't a tool steel - 'cause if they went to the expense of decent steel, they would have hardened it. Maybe, though, they were hard originally and lost that hardness. If they are low carbon, you have to add it. Kasenit is indeed the choice. I don't know what hardware Mert frequents though, because even the welding suppliers near me don't stock it anymore. To build up a decent case thickness, it's a good idea to keep the heat on for a few minutes while the piece is covered with Kasenit. Dip it a couple of times. You'll note Mert said nothing about tempering. With a soft steel core, there's not as much need to temper as there is with a solid high carbon tool. The teeth might be a bit more prone to chipping, but they may just work better. When the original poster talked of tempering the tool I presume he played the flame right on the teeth - which may have annealed them. If he really wants to anneal, it might be better to not hit the teeth with the flame, but let the colors run to them. Those teeth are small, and will heat up too quickly in the flame. Which could also decarburize them in the hardening step. John Martin ------- Date: Wed, 01 Feb 2006 19:49:03 -0000 From: "James Davis" Subject: Re: A wee bit off topic - flame hardening of steel You can harden them with an acetylene torch by heating them bright red, then turning off the oxygen and applying the smoking yellow acetylene- only flame (almost pure carbon) to the teeth. Do this several times, then reheat and quench in water. Since the jaws are already soft and only the teeth will be hard, you can temper them to a straw color and should be good to go. What you will have done is case harden the teeth. Jim in Maine ------- Date: Wed, 01 Feb 2006 14:59:42 -0600 From: "Adam Meister" Subject: Re: A wee bit off topic - flame hardening of steel Thanks for the tips Mert, I'll try the grinder test. It looks like I broke a small chunk out of one of the teeth, not smashed them as previously thought so maybe I did harden them after all? Kinda hard to tell. I'd like to get this done so I can blue them with gun blueing (spelling?) and put them to work in my tool kit. I appreciate anyone willing to pass along some of their wisdom. Thanks, Adam ------- Date: Thu, 02 Feb 2006 01:51:38 -0000 From: "Dennis Pasek" Subject: Re: A wee bit off topic - flame hardening of steel Close. Low carbon = Low *hardenability* and there is only so far that you can go by adding carbon at the surface. But, you need to heat treat according to the alloy content. Mert's suggestions are the best you can get for empirical work when you really don't know what you have. That method works especially well for plain carbon and high carbon, low alloy steels. It will not work as well for high alloy tool steels, partly because those materials require much longer tempering times. Remember, high carbon is needed for tool steels, but high carbon alone does not make for tool steel. Spring steels are often near 1% carbon, but with little or no alloy content as with AISI 10100, and are not very useful as tool steels. The alloy additions provide additional properties like high temperature stability (as for HSS), extra toughness in the hardened condition (as with S7) etc. If that pair of pliers is made of tool steel, it is probably still too brittle to use, thus the chipped tooth. If you (Adam) have any big scrap metal recyclers in your area, they might have an X-ray fluorescence scanner that could quickly identify the type of alloy used to make those pliers. This page: http://www.pvsteel.com/ToolSteelBook.asp has some good info if you are interested. Look at the "Tool Steel Selector" link near the bottom of the page. This suggests what types of tool steels to use for various applications. Then look at the "Uses & Heat Treat Data" links in the second column. These data sheets don't specify, but tempering times for tool steels are typically 1 to 2 *hours* at the indicated temperature, and sometimes double tempering is required. Also, while a water quench is appropriate for plain carbon steel, it is much too harsh for most tool steels, and could cause cracking. (Remember the advice to never water quench HSS tools after grinding for this reason.) Some better data sheets are available at: http://www.crucibleservice.com/datasheets/index.cfm Tool steel types are described at: http://info.lu.farmingdale.edu/depts/met/met205/toolsteels.html and anyone interested can go up one level for a full intro. Sorry for the length of my post, but there is a lot more to heat treatment (and a lot more that can go wrong) than you might think. Dennis ------- Date: Thu, 02 Feb 2006 07:51:11 -0600 From: "Adam Meister" Subject: Re: A wee bit off topic - flame hardening of steel Thanks for the added info John. I compared the amount of sparks of the grinding wheel and the pliers and an old file appeared to be the same. So I can assume the pliers are (or were) high carbon steel, I think that I messed up trying to temper them with too much heat. All may be a non- issue as Paul sent me a link for the exact pliers I'm looking for brand new. I'm kinda growing attatched to these old pliers though, so I may finish them anyway. They'll look good next to my 1937 Craftsman 12" x 36" lathe when it's done. Thanks, Adam ------- NOTE TO FILE: The following conversation was extracted from a sherline group discussion dated Jan 2, 2007 initially titled Miniature Wood Turning on the Sherline. The original tool choice discussion can be found in the file "Turning Wood on the Metal Lathe" on this site. NOTE ALSO: The title gets renamed several times during this conversation here about heat treating. If someone used a search engine in the archives he would be unlikely to find all the pieces of this discussion. Hence the advantage of checking this site, where like-stuff gets stuck together ... usually ... sometimes ... okay, maybe ;-) ------- Re: Miniature Wood Turning on the Sherline [sherline group] Posted by: "dkaschnerx~xxcomcast.net" Date: Thu Jan 4, 2007 8:22 am ((PST)) Tom Bank wrote: >> I would guess that the Henry Taylor set offered by Lee Valley would be good, probably as good as the Sorby tools. The Lee Valley U.S. made set I would question. It is W-1 steel. It should be O-1 or some other Oil tempered steel. << "Alan Haisley" wrote: > Tom, I don't know O from W from A or whatever with regard to tool steels except that the letter relates to the tempering medium. Could you say something about why the oil hardening is more appropriate for this than the water hardening. Also, where and when would you use the water hardening steel. Thanks, Alan Haisley < Interesting comments... O-1 is a deeper hardening steel than W-1. Both steels are great for tools that are not subjected to extensive heat when in use. As part of the heat treatment process both (all) steels require tempering after the quench. Quenching, when accomplished properly, will yield a very hard but brittle tool. In this state the steel is so hard it cannot be cut with a file (the typical test) but the edge will chip very easily yeilding a less-than-useful tool. Drawing the temper involves heating the steel to a subcritical temperature in order to soften the steel. We are trading off hardness for a softer, but tougher, edge. The degree of tempering is dependent on the intended use for the tool. For example, swords must be tougher than knives. A sword takes more impact and would shatter if tempered like a small knife. A quick gauge of temper is usually expressed as the color that is seen on the steel surface. This color is caused by oxidataion on the surface. Colors may range from light straw to deep purples... purples being the softest (lowest Rockwell hardness rating)... again, soft is not necessarily bad! Purples may be warranted for the body of a hammer head. Often harder zones of a tool are backed by softer, tougher zones. This is a differential temper. When used in cutting tools, may allow a harder edge because of the soft, tough backing. IMHO, W-1 is easier to use if you want a differential temper due to its shallower hardening characteristic. (As a rule faster steels are shallower hardening than slower steels.) So both steels require tempering to the same hardness for a given application. W-1, being a water hardened steel requires a 'fast' quench in order to get 'under the nose' in time, typically less that 1 second... i.e., the temperature must be lowered from critical (non-magnetic) to below Ms in less than one second to achieve maximum hardness (don't ask me to explain this one - lots of metalurgy going on here :-). O-1 is a 'slower' quench steel, i.e, it can take longer (if I recall correctly, up to 6 seconds?) to get below Ms and still achieve maximum hardness. In fact if you were to quench O-1 in water (a relatively 'fast' quench medium you would most likely hear the dreaded 'ping'.. and your steel is broken ;-) O-1 cannot take the stress of a fast quench. The extreme internal stresses caused by a fast quench of O-1 would tear it apart. That said (sorry to ramble, but man, I love heat treating :-) I tend to like HSS for turning tools. The reason is that turning generates a lot of heat at the edge of the tool from friction. This heat will tend to overly soften the tool edge... ie. when the edge turns blue in simple carbon steels it is usually too soft to retain a good edge for any period of time for turning. You will be resharpening much more often once the edge blues and/or you will need to grind away the softer steel to get back to a reasonably hard zone that will hold an edge longer. OTOH, HSS is much more 'red-hard', i.e. it can turn blue or purple and not soften the way simple carbon steels do. (BTW, W-1 and O-1 are relatively simple carbon steel.) For this reason all of my turning tools are HSS. My knifes, hand plane irons, etc... are simple carbon steel (O-1, W-1, 1095, etc.). Applications like cutting leather, carving wood, planing wood, etc. don't typcially generate enough heat at the edge to affect the temper. Turning wood does. Long and short of it... IMHO, W-1 vs. O-1 is not as critical in a turning tool as simple steel vs HSS. IF you have W-1 and no O-1, and are aware of the perils of overheating go for it. If you can get a hold of some HSS to use for the tool, even better. Sorry to ramble, just let me know if the messages get too long-winded. :-) Dan ------- Re: Miniature Wood Turning on the Sherline Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Thu Jan 4, 2007 9:01 am ((PST)) Hey! You forgot "Tempil Sticks". If you want great tools that do not soften even when red, get some Stellite. Jerry G (Glickstein) ------- Re: Miniature Wood Turning on the Sherline Posted by: "dkaschnerx~xxcomcast.net" Date: Thu Jan 4, 2007 10:22 am ((PST)) Jerry: Great point! Tempil sticks are an excellent and accurate way to measure temperature. I used to use them a lot. But only for specific temperature ranges (for heat treating steels that I commonly work with). I should keep a larger (temperature) range on hand. Stellite... not familiar with it. Is it essentially S-7? I use that a lot for dies that will take major battering at high temperatures (like custom dies I make for my power hammer). Is Stellite tough to grind? Some of these steels wreak havoc on abrasives. I also have a tough time forging air-hardening steel to shape. Once they are heated to red and beyond, the steel will just not move under the hammer and it takes a fairly sophisticated (and long) heat treat schedule to anneal. I'd be interested to hear more about Stellite. Always looking to increase my steel-stash. :-) Dan ------- Re: Miniature Wood Turning on the Sherline Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Thu Jan 4, 2007 2:01 pm ((PST)) Hi Dan, Google out Haynes Stellite.... If you can find any, grab it! A bitch to grind, but it is the best toolbit. Will not chip like carbide. Will not "fold up" like HSS at really high temps where the cutting edge is actually red! I think VR/Wesson Tangtung "G" is similar. (Very high "red" hardness.) Would you believe that some guys used to draw with the Tempil Sticks, thinking they were crayons...? :) Later, Jerry G (Glickstein) ------- Re: Miniature Wood Turning on the Sherline-Hardenable Steel Grades Posted by: "Tom Bank" trbankx~xxpaonline.com eimcr Date: Thu Jan 4, 2007 2:24 pm ((PST)) Alan: The Sorby and Henry Taylor tools are Sheffield steel. I like that steel for cutting tools, whether woodworking or fly fishing hooks. (Get the hooks from Partridge of Redditch, still the best after over a hundred years!). If you know A, O, and W, you know they stand for the hardening mediums: air, oil, and water. Air hardening is special purpose, used in situations where you don't want to take a chance on the piece you are making bending in the process of hardening it. It costs twice as much as either of the other two. Oil hardening is what you normally use for non-metal cutting tools: knives, chisels, gouges, etc. Water hardening is a general purpose hardenable steel, inexpensive and easily machined before hardening. As MSC puts it, it is frequently used without hardening for maintenance applications. If you are making a cutting tool for a specific application, a one time use and then throw it away, W-1 will probably be good enough. I am in the process of setting up to make four pairs of shutters. I will be using a special decorative edge on the side rails, 32 ft. of pine. I made a special router bit to do the job using W-1. It should handle that job and then will probably never be used again. Regards, Tom Bank ------- Excuse me while I step into a phone booth and adopt my heat treater Posted by: "Bill Vallejo" tankyank_1x~xxmsn.com Date: Fri Jan 5, 2007 4:16 am ((PST)) "Jerry G" wrote: > Hi Alan, > Let me jump in here with my .02 cents worth. > "Hardening" is an all encompassing term that really should be properly > identified as "Heat Treatment of Metals". It is an exact science. > The procedure is to heat the tool steel (selected by the percentage > of carbon) above the "critical temperature" and then quench it. > This changes the molecular structure of the steel. > The quenching medium can be oil, water or air. > The application is the key..... That determines the choice of the > right tool steel, the right quenching medium, etc. > The tool steel can be heated using a heat treating oven, or a > torch, or in a salt bath. > I am just "skimming" the information to give everyone a smattering > of the subject. More info is available.... > Just ask! :) Regards, Jerry G (Glickstein) Hardening is but one operation in the all encompassing term "heat treating" which also includes tempering, stress relieving and annealing to name just a few. Any type of high carbon and alloy tool steel will crack and even shatter if quenched in water and for some, even oil is too fast a quench medium and must be air quenched. After the quench (hardening) the material is then tempered. Tempering accomplishes two things at once. Firstly, it relieves the internal stresses induced in the material when quenched and is also how the desired hardness is fine tuned. As quenched, all hardenable steel is much to hard and brittle. The higher the tempering temperature, the softer and less brittle the material will be. Space does not permit me to even scratch the surface of heat treating but it isn't as exact a science as we wish it was. p.s. The term "oven" annoys forgers and heat treaters to no end. We use furnaces, bakers use ovens. No one's probably unaware of it at this point but yes, I do have the attitude of one that has mastered the magical art. It has also mastered me more times that I'll ever admit. ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Fri Jan 5, 2007 6:10 am ((PST)) Hi Bill: If you don't think "heat treating" is an "exact science, Check with Alfred Heller..... :) Later, Jerry G ------- Re: And another thing... Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Fri Jan 5, 2007 6:17 am ((PST)) Hi Bill: Why should professional people get annoyed to no end? The terms furnaces, ovens, are used interchangeably..... If you put a loaf of bread in your furnace, will it not bake? If you achieve enough heat/temperature, then an oven with the proper controls is capable of heat treating. Later, Jerry G (Glickstein) Student of many "arts" Master of none...... :) ------- Re: And another thing... Posted by: "Carol & Jerry Jankura" jerry.jankurax~xxstratos.net Date: Fri Jan 5, 2007 6:21 am ((PST)) Hi, Bill: Glass makers - the BIG ones that produce all of those bulbs you screw into the sockets so you can see your furnaces - use ovens, not furnaces, to anneal their glassware in a big way. The name of the monstronsity that does the work is a "lehring oven" in honor of the person who developed the process. Since annealing is part of heat treating, I guess we can say that either term is correct? :) Jerry Jankura Strongsville, Ohio ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "dkaschnerx~xxcomcast.net" Date: Fri Jan 5, 2007 8:19 am ((PST)) Bill: Were you referring to high carbon alloyed steels or high carbon and/or alloyed steels? Just wondering because I quench in water even more than oil. For me, oil is so messy with the smoke and all, of course, now that I am starting to use peanut oil it does smell a lot better. :-) And it has a whole lot less chemicals for me to worry about inhaling... W-1, 1095 etc... quench in water nicely (especially with an interrupted quench). They also produce a very nice hamon that, at least for me, is tough to get with an oil quench. I tend to use simple high carbon steels for my woodworking cutting tools. They work fine and, for me, water is so much more convenient... but like I mentioned in a previous post, if the tool is to be used in a high heat application, I get more exotic in my choice of steel and subsequent heat treatment. It's just what works for me. Others get better results with other steels. BTW, I understand your point about furnace vs. oven... Had this discussion more than once before with others from our local Guild. Guess I'm not too exacting... I tend to think I have a forge (actually a few propane forges) that some would refer to as a furnace and a couple of electric heat treat "ovens" (at least that's what I usually call them - when they are behaving :-) If I was a ceramics-guy I would probably call them a "kiln". Heck, that's where I got a lot of the parts for them the local ceramics shop. Ceramics kiln people have a lot of experience with high-temperature equipment, heating elements and refractory, so I hang around them a lot. :-) The electric heat treat ovens see a lot of service for normalizing (for very controlled, reducing heat cycles) and annealing. Tempering is another service they are pressed into, although it wasn't too long ago that I used the house oven and/or toaster oven. My wife and I get along a lot better after I built the heat treating ovens (especially when I missed a little oil from a quench... she wasn't very enamored of me at those times :-) Any way, great thread... sorry if I get a little off topic. Good to hear from so many people on this topic! Dan ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "Bill Vallejo" tankyank_1x~xxmsn.com Date: Fri Jan 5, 2007 12:12 pm ((PST)) I didn't phrase that quite right. I actually meant to say any hardenable high carbon steel. It's not really an issue in thin cross sections less than 1/4 to 1/2 inch, especially with an interrupted quench, but get them into the temper furnace ASAP. For small hobby applications, any type of oil will work very well and you're right about food grade oils smelling better and being non toxic. I must say that you know what you're doing. This is all pretty much the same procedures I always used when making small forging tools and the like. ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Fri Jan 5, 2007 10:50 am ((PST)) Dan: Just a little tip. In regard to the smoke you mention with oil quenching....The faster you dunk it, the less smoke. If you are really slow, keep a fire extinguisher handy..... ! Later, Jerry G (Glickstein) P.S. What the hell is a "hamon"? ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "dkaschnerx~xxcomcast.net" Date: Fri Jan 5, 2007 1:51 pm ((PST)) Good point. I keep a fire extinguisher and a metal top. If I get a flare up the metal top usually takes care of it. Never had to use the fire extinguisher but it's always there and I make sure the charge is good. For quenching small parts I used to get lazy and just use motor oil in the open air... but now that I have my forge set up and a handy source of peanut oil it's just as easy to use that... heck, I've been known to be a little slower than I should just 'cause I like the smell of peanut oil :-) Interesting, peanut oil seems to be a fairly 'quick' oil quench medium. Does a great job with 5160, which by the way, is a steel I like a lot also ... makes a real tough blade with the right heat treat. Dan ------- Re: Miniature Wood Turning on the Sherline Posted by: "Ron Ginger" rongingerx~xxadelphia.net Date: Fri Jan 5, 2007 6:26 am ((PST)) Tom, good info on heat treating, thanks. How about a bit more on the Air hardening material. I have to make a very long tap- 1 1/8dia, 12 pitch, 14 inches long threaded area with a 14" long pilot on the leading edge. This is to tap staybolt holes in a boiler for the WW&F Ry #9. The holes in two sheets about 12" apart must have a continious thread. From my previous experience I know things like drill rod warp badly when quenched. Will Air hard likely work- I have only a torch to heat this with, not a proper furnace. The good news is it only needs to be a really hard cutting edge over about a 6" length near the center of the tap. ron ginger ------- Re: Miniature Wood Turning on the Sherline Posted by: "Tom Bank" trbankx~xxpaonline.com eimcr Date: Fri Jan 5, 2007 7:46 pm ((PST)) "Ron Ginger" rongingerx~xxadelphia.net wrote: >>Tom, good info on heat treating, thanks. How about a bit more on the >>Air hardening material. Ron: My guess would be that the air hardening steel would be the best for that reason. When heat treating it, I would also cut a short section on the tap handle end of the thing to a diameter I could chuck in a variable speed electric drill. Then suspend the drill with the new die in the drill so the die is hanging vertically, turn the drill on to a low speed, and heat the length of the die that will do the cutting. That way the heating will be as even as you can get it, which will help in avoiding warp. Keep it turning until it is reasonably cool. Beyond that, are you talking about the *REAL* WW&F #9? If so, WOW! What a project to be involved in! If that's the case, you might consider talking with people who understand such things better than I do. I assume you are coming to this year's Cabin Fever in a couple weeks. If you could arrange to stay over Mondayor get here early, the Strasburg Railroad is just across the river from York (figuratively speaking), as is the Pennsylvania Railroad Museum (actually, across the street from each other). The people there do all kinds of maintenance and reconstruction on locomotives. A couple years ago I watched a video at a club meeting of their team "turning" the front sheet for a Belpaire firebox. Not the kind of job you do on a lathe; this task is performed with a number of very large torches and large sledge hammers. The sheet started out flat. A moderate sized hole was cut in it and then the edges were "turned" down to fit very accurately in the back end of the boiler. That was followed by turning the sheet over and then the outside edge sections were "turned" back the other way (with rounded corners) to fit onto the squared off firebox that was loved by the PRR and GN railroads. Quite an awesome video. That team could build an engine from scratch. If you talked to them, I'm sure they could give you pointers on what the tap you need should look like, how to make it, and how to use it. They might even be willing to loan you one. I wish you success, Tom Bank ------- Heat treating Posted by: "vikebo" vikebox~xxhome.no vikebo Date: Fri Jan 5, 2007 6:26 am ((PST)) Seems like it is a lot of knowledge on heat treating here. I am not heat treating anything at the moment, but have made some tools earlier. I have previously tried to heat treat some things I have made from "Silver steel". From what I have heard silver steel is tool steel with enough carbon to enable hardening. One supplier said theirs was actually Sandvik 20AP (link below). http://www.sandvik.com/sandvik/0140/SM/se01240.nsf/ f9aff13490287b65ea2564f50042c670/55011b253b2fa62ac125689300656e85! OpenDocument I am not too happy with all my results. Since I have no furnace I have used a propane flame to heat the steel for the hardening. I have been heating until "cherry red", but not sure I have always kept it at that temperature long enough. Is the timing important to allow the whole part to get the correct temperature, or does the metallurgic process also take some time? The parts have been quenced in water (have been told to use water at room temperature without bubbles in, let it stay for a day before use). After quenching I have polished the parts and tempered them until "light straw" on a plate. I have also used the rear part of HSS drills sometimes, it is available in many diameters and easy to find. Usually it is not hardened to avoid damage to the chuck jaws so it is possible to machine it before heat treating. Any recommendations regarding heat treating of HSS (like quenching media)? Eivind -------- Re: Heat treating Posted by: "Alan Haisley" alanhyx~xxadelphia.net Date: Fri Jan 5, 2007 8:47 am ((PST)) Eivind: To tell if the initial heating is hot enough, you should try a permanent magnet. When heated to a high enough temperature steel loses its magnetic properties. Also, depending on the size of the piece you may need more torches since you really want to get the whole piece to the "critical temperature" at about the same time. If you hold it hot too long, it can lose carbon to the combustion process. Commercial heat treating often uses either special furnaces with controlled atmosphere or a stainless steel foil wrapper to keep the heated part away from oxygen. Of course the sizes that we work in on Sherline tools is small enough that I suspect we do fine just bringing a piece up to temperature for a couple of minutes. One point in your note concerns me after reading Sandvik's information. It sounds like you are leaving the steel in the quench overnight before tempering. Sandvik says to temper immediately after quenching. Sometimes MAPP gas torches are recommended - propane flame is not considered hot enough. Wikipedia has an article on MAPP gas. Personally, since I have a propane torch and don't have a MAPP torch I use that. Of course I have no hardness testing equipment and so can't really tell how successful my attempts are; and I have never attempted HSS at all. Alan Haisley ------- Re: Heat treating Posted by: "Alan Haisley" alanhyx~xxadelphia.net Date: Fri Jan 5, 2007 8:20 pm ((PST)) Eivind, I think your question about HSS got forgotten so I'm reposting the sense of it. Suppose I cut off the soft end of an old, worn out HSS drill to make a little tool - perhaps a cutter for a small boring bar or something. Let's take three cases, since we work little: 1) I want to use a little stub from a 1/16" drill. 2) I want to use a piece of a 1/8" drill instead. 3) I'm using a big piece, a 1.5" piece from the back end of a 3/4" drill. In each case, I'd like to end up with the business end as hard and tough as I can get it while the rest is tough enough to be part of a lathe tool. Alternatively, I am making a really hard axle or pivot shaft or something and want to harden the whole thing. How do I make this softer HSS hard? What do I do differently in heat treating, quenching, and tempering? Are there specific times, temperatures, and quenches that you can suggest? If I missed the mark on this for you Eivind, please chime in with changes or clarifications. Alan Haisley ------- Re: Heat treating Posted by: "vikebo" vikebox~xxhome.no Date: Mon Jan 8, 2007 2:09 am ((PST)) Alan: Good point about the magnet, I have heard it before, but had forgotten. Will try to remember that the next time. The thing you mention about the steel losing carbon to the combustion process may be the reason that some of my parts have been soft after hardening. The datasheet says 3-6 min "soaking time" for parts of less than 5 mm. Since I have not got a controlled atmosphere and a wrapper foil would make it hard to know the temperature, I will just heat up to the correct temperature and quench. I usually temper as soon as possible after hardening, but only if the hardening was successful :-) However, the steel usually needs to be polished before tempering to see the colors when tempering. I was told by someone I knew that it was an advantage to let the water stay overnight before quenching. The reason, as also mentioned in later posts by several posters, was for the bubbles to get out. Dan also has a good point on making the part oversize so the decarbonized layer can be removed with a grinder. Thanks for all the suggestions and help! Eivind p.s. I guess you got all the points I had thought of, and a few extra too. Normally I harden things to be used as cutting tools, but other applications for HSS could also be of interest. ------- Re: Heat treating Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Fri Jan 5, 2007 9:37 am ((PST)) Hi Guys: Tempering ASAP is always recommended because of the internal stresses built up in the tool from the hardening process. You might fish out your "overnight water soak" to discover some cracks and fissures... especially at stress riser points like sharp internal corners without fillets, etc. Later, Jerry G (Glickstein) ------- Re: Heat treating Posted by: "Smitty" TORYRANGERx~xxwi.rr.com Date: Fri Jan 5, 2007 12:46 pm ((PST)) The bit in his discription is about letting the water sit overnight to normalize, not about quenching the part overnight. ------- Re: Heat treating... Normalized Water!!!??? Never heard that before. Posted by: "Alan Haisley" alanhyx~xxadelphia.net Date: Fri Jan 5, 2007 7:58 pm ((PST)) Smitty wrote: > OK, you caught me, I just pulled that word out of my butt!. If you let > water sit I think it will loose some of the oxygen that is suspended > in it. I think that is what he is talking about. Smitty If you let water stand, it will lose much of the dissolved gasses: nitrogen, oxygen, CO2, and argon principally in decending order of concentration - although not all since eventually equilibrium is reached. To the taste it becomes "flat". (It will also lose most of its dissolved chlorine if it is American water). Perhaps in that state, gasses remaining are either less apt to move to the surface of the steel or there is a change in specific heat that slightly changes the rate of quench for the better. Alan Haisley ------- Re: Heat treating... Normalized Water!!!??? Never heard that before. Posted by: "Keith Green" ksggx~xxtelus.net Date: Fri Jan 5, 2007 9:53 pm ((PST)) Though I've not heard of it, I think the idea might have a little merit: I remember back in trade school when we had to quench some parts we'd heat-treated, one of the prime culprits of a bad quench was the air bubbles coming out of solution in the quench-water and forming on the part. These caused uneven quenching if you didn't stir vigorously to get them off. Also, I recall that chlorine getting into the metal will cause failure in the long run as it does something to the surface layers that promotes metal-fatigue. I doubt that there's all that much chlorine in tap water, but that might be part of the reason to let the water stand a while before using it. The chlorine dissipates out of tap water if you let it stand a while or boil it. Keith ------- Re: Heat treating Posted by: "dkaschnerx~xxcomcast.net" Date: Fri Jan 5, 2007 10:42 am ((PST)) Jerry, I'll second that... learned the hard way about not tempering ASAP. Waited until the next day and when I went to get the blade it was broken. Now I try to temper 'real quick' after the quench. Alan, good point about decarb. For larger pieces, like a knife blade, Iju st leave a little extra steel to grind away and take off the decarb layer with the grinder. Like you said, given the size of the parts we are making for the Sherline I would guess that final sharpening would get all of the softer steel without any special precautions. BTW, you don't really need a hardness tester. The easy way is to grab a file after the quench and see if it skates across the surface. I think files are typically in the neighborhood of Rc 65, so if the file won't cut, you have succeeded. Another suggestion is to be sure and not get the steel too hot, i.e., to far above the critical temperature (non-magnetic). This will tend to give the steel a coarse grain which can weaken it. May not have to worry too much using a propane torch, but on small parts you may still get plenty hot. Just test with the magnet often and you should be OK. Dan ------- Re: Heat treating Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Fri Jan 5, 2007 11:41 am ((PST)) All: As mentioned, especially for small parts, the SS quenching bags are great with three caveats: 1. Add some temps to allow for the insulating properties of the bag. 2. When loading, watch out! The inner edges of the opening at the top of the bags are razor sharp! Handle with care. 3. When going to quench, I always keep a three cornered machinist's scraper handy, and stab the bag repeatedly as I lower the bag into the oil... To allow the oil in to do the job. Then, you get some smoke signals...... :) Later, Jerry G (Glickstein) ------- Hamon Posted by: "Nelson Wittstock" k8djcx~xxzoominternet.net Date: Fri Jan 5, 2007 11:41 am ((PST)) Jerry asked, "What the hell is a "hamon"? It's a kind of sandwich -- hamon rye! Nelson ------- Re: Excuse me while I step into a phone booth and adopt my heat Posted by: "Smitty" TORYRANGERx~xxwi.rr.com Date: Fri Jan 5, 2007 1:13 pm ((PST)) In swordsmithing , *hamon* (??, /hamon/^? ) (from Japanese , literally "blade pattern") is a visual effect created on the blade by the tempering process. It is the transition between the region of harder martensitic steel of the blade edge and the softer pearlitic steel of the back of the sword. This visual effect is from the harder Martensite crystals in the steel of the edge which make the steel harder. This difference in hardness is the objective of the tempering process, the visual effect is purely a side effect. Many modern reproductions do not have natural hamon; their hamon is faked via various processes such as acid etch , or more crude ones such as wire brushing . Some modern reproductions with natural hamon are also subjected to acid etching to enhance that hamon's prominence. From wikipedia: http://en.wikipedia.org/wiki/Hamon_%28swordsmithing%29 Smitty ------- Re: Hamon Posted by: "dkaschnerx~xxcomcast.net" Date: Fri Jan 5, 2007 1:31 pm ((PST)) Sorry. I got carried away. After sending that message, I realized that I used a term that wasn't previously defined. A hamon is sometimes (inappropriately) called a 'temper line'. Bladesmtihs are fond of hamons, especially when making Japanese weapons (although I think they are just plain cool looking). A good hamon shows a nice frosty line between the harder edge steel and the softer steel in the blade's spine and a lot of swirling activity in the edge portion and a color differential between the soft and hard areas of the blade. Hamons are associated with a differential heat treat where one specifically leaves the spine soft (and tough)... because of the tough backing you can generally get away with a harder edge and avoid chipping and cracking. To bring out the hamon you etch the blade in some acid after heat treatment. Some use warm vinegar or lemon juice, others diluted ferric chloride (technically not an acid, but a salt) others even go so far as to use diluted muratic acid... either way, because difference in hardness the acid will attack the steel a different rates yielding the color difference and really neat patterns in the steel. Japanese bladesmiths have all kinds of names for different kinds of patterns in the hamon. Me, I just like their look. To me they also say "this is a high performance blade"... kind of braggin rights :-) 'cause you don't often find them on mass produced blades. I'm working on a set of kitchen knives for my step daughter right now that are differentially heat treated and etched and polished to reveal the hamon. Funny thing about a hamon. Most bladesmiths find it hard, if not down- right impossible, to get a hamon in an oil quench. Too slow. Need a quick medium like water or brine. That pretty much dictates W-1 or a 1090 / 1095 steel... even though these are water quenched, I use an interrupted quench (3 seconds in, 3 seconds out until I can handle it with bare hands) to reduce the stress and avoid broken blades... fast quenches create a huge amount of stress in the steel. Oops... there I go again, with the long messages. :-) Dan ------- Re: Heat treating [yes all these are still in the sherline group] Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Sat Jan 6, 2007 12:20 am ((PST)) January 05, 2007 Alan Haisley wrote: >>That reminds me. I think that either in an ENCO ad or a J&L ad there was an item of a set of "hardness testing files". I assume that what these are is a set of files of varying hardnesses for rough testing. << Hi Alan, and all: Yes, that is correct. The files range from 40 Rc to 65 Rc, in 5 Rc increments. Me? I'll take the Rockwell Tester any time. :) Jerry G (Glickstein) ------- Re: Heat treating Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Mon Jan 8, 2007 2:26 am ((PST)) Hi Eivind. Another good tip for you and whoever, I used (successfully) a glass bead blaster to remove the scale from hardening (heat treating), when we ran out of Stainless Steel bags, etc. Later, Jerry G (Glickstein) ------- Re: Heat treating Posted by: "Tim H." tim-henryx~xxmicrotune.com Date: Mon Jan 8, 2007 3:35 am ((PST)) Hi, I just hardened some O-1 parts the other day. A product that I use to keep oxidation under control is "P B C" Non-scale compound from Brownells. http://www.brownells.com/aspx/NS/store/ProductDetail.aspx? p=1122&title=PBC?%20NON-SCALE%20COMPOUND You heat the part to 500 degree F (or so) and the powder sticks to it (partially melts on). Heat treat the part and if you quench in oil the coating comes off later in boiling water. I haven't quenched in water but that would also remove the coating at the same time. Now when you temper you are going to get a little oxidation but you can use that to gauge when to stop. Since 500 degrees is in the tempering range you couldn't re-coat with "P B C". Tim H. ------- Re: Heat treating Posted by: "Tom Bank" trbankx~xxpaonline.com Date: Mon Jan 8, 2007 8:18 am ((PST)) This has been a really interesting thread for a number of us. Lots of information exchanged. My experience with heat treating has been spotty, but dates back to when I was in Junior High, back in the golden days of the early '50s. In metal shop one of the projects we boys had to make was a cold chisel: hacksaw off a piece of 1/4" hex rod, file the end to shape, then heat treat it with Kasinet in one of several small furnaces which were about 8" to 10" long by 4" to 5" wide at the mouth and maybe 3" high, again at the mouth. These little gems were composed of iron castings with a custom made fire brick interior and were mounted on single shaft pedestals with flared bases. Natural gas was fed in along the sides of the furnace floor and I don't remember any hood to carry off the heat or fumes. As I remember it, for each furnace six or eight twist handle valves regulated the gas feed to keep the temp even across the chamber and one master valve turned the gas on and off. There was no door on the mouth of the thing. I thought that those things were the cat's meow, and I always wanted one. Unfortunately, I moved away from there and wasn't on hand when the school system dumped all the metal shop equipment. But I'm wondering, are little furnaces like that still available on the market? Where would I go looking for one if I decided I had money that needed to be spent on such a worthy cause? And what should I expect to have to pay for one, either new or in reasonable condition? Regards, Tom Bank ------- Re: Heat treating Posted by: "dkaschnerx~xxcomcast.net" Date: Mon Jan 8, 2007 11:06 am ((PST)) Tom: Bladesmiths/blacksmiths make them all the time. You can buy or make one. I have made a few... different sizes, one for forge welding, etc. They are relatively easy and inexpensive. Most bladesmiths/blackmsiths find that one size does not fit all jobs and so build a new forge when the need arises. Some follow the KISS philosophy and others add controllers, pyrometers, etc. The biggest difference is that most of these forges run off on propane. There are also natural gas forges and electric heat treat ovens out there too. (I also have a couple of heat treat ovens that I made.) If anyone is interested I can dig up a few links to good 'starter' sites. Dan ------- Re: Heat treating Posted by: "WILLARD WHEATON" wwheatonjrx~xxverizon.net Date: Mon Jan 8, 2007 11:09 am ((PST)) Tom: You can make your own, if you're so inclined. Check out furnaces and burners in the following site: castinghobbyx~xxyahoogroups.com Willard E. Wheaton Jr. ------- Re: Heat treating Posted by: "David Clark" dcclark111x~xxcomcast.net Date: Mon Jan 8, 2007 11:36 am ((PST)) Tom: Take a good look around Lindsay Books: http://www.lindsaybks.com/prod/index.html for example: http://www.lindsaybks.com/dgjp/djgbk/ffurn/index.html For those of you not familier with these publications; be prepared to have your entire life sucked into this stuff. DC ------- Re: Heat Treating -- Small Furnace or Oven Posted by: "Tom Bank" trbankx~xxpaonline.com eimcr Date: Mon Jan 8, 2007 9:38 pm ((PST)) To those who replied, many thanks. I think there is enough info to get me started. Since I don't have natural gas here, knowing that propane is acceptable sounds good. My wife wants me to get a medium size grill next summer. I assume I can grab the tank when her back is turned. As for Lindsay, I will be going to Cabin Fever the end of the month, a good place to pick up any of their offerings. Regards, Tom Bank ------- Re: Heat Treatment of Metals [sherline] Posted by: "Bradford Chaucer" bjchaucerx~xxcharter.net Date: Thu Jan 11, 2007 10:51 am ((PST)) I've been reading the posts on heat treating with interest, and have a question or two. 1. When doing the initial quench to harden the steel, is it necessary to bring the metal back down to room temp or is it just necessary to bring it below some point, for instance the tempering temp? 2. When tempering, do you quench after the heat soaking period, or do you merely allow it to cool in air. Thank you in advance. Regards, Bradford J. Chaucer ------- Re: Heat Treatment of Metals Posted by: "Jerry G" chieftoolmakerx~xxearthlink.net Date: Thu Jan 11, 2007 11:25 am ((PST)) Hi Bradford: I quench the tool by putting it in the oil or water bath, then let it sit in the wire basket, or on a suitable surface if it is to be air quenched. And when it reaches the temp of the quenching media, which is slightly raised by the immersing, do any cleaning necessary to remove scale, etc. Then, the part goes into the tempering oven(furnace). Some applications require that the tempering oven (furnace) be reduced in temps a little at a time over a specified period of time. The same quenching media should be used when quenching from "tempering" as from "hardening". Regards, Jerry G (Glickstein) ------- Book on heat treatment [sherline] Posted by: "vikebo" vikebox~xxhome.no Date: Thu Feb 8, 2007 11:41 am ((PST)) The subject of heat treatment was up on the group not too long ago. Since several people seemed interested in the subject I will mention a source of some information. When I recently packed my tings and moved to another city I found a book which I had not yet read. It is called "Hardening, tempering & heat treatment (for model engineers)" by Tubal Cain (isbn 0-85242-837-5). I have now read most of the book and found the information very useful. It explains things with curves, figures and understandable text. There are also colour charts to show what colours you get at different temperatures in the furnace and when tempering. BTW: I have no connection to the author or book in any way. Eivind ------- Re: Book on heat treatment Posted by: "vikebo" vikebox~xxhome.no Date: Thu Feb 8, 2007 12:43 pm ((PST)) "Jerry G" wrote: > Hi Eivind, Do they show or mention optical thermometers? Or pyrometers? > To see the colors in the furnace? Regards, Jerry G (Glickstein) Hi Jerry: There is an appendix on thermocouples and pyrometers; I have not read that yet. To cite the text below one of the pictures: "Indications of colour/ temperature using a 3 x 4 in. steel plate photographed in the author's muffle furnace". Six pictures are shown, at 700, 725, 750, 780, 800, and 840 degrees. The idea is to estimate the temperature based on the colour of the steel part. Some problems with the method are also mentioned. I guess the main advantage is low cost, and since the book is written for model engineers that can be an important one. (He also mentioned the differences between european and american methods, which you told about in an earlier post.) Eivind ------- Date: Fri, 12 Oct 2007 12:40:20 -0500 From: "Ken Meltsner" Subject: Re: [OldTools] Super secrets of samurai swords... A long time ago (~1980), we made samurai sword-like knives in metallurgy lab at MIT. Prof. Ogilvie had examined sections from real swords (from Boston's MFA, I believe) and we used clay in different thicknesses to approximate the real thing. I apologize for any memory lapses -- my class notes are either buried in the basement or left behind in one of my repeated moves. Basically, the science is: * Sword is coated in clay to slow down the rate of cooling during the water quench * The back of the sword is coated with a thick layer so that it cools the slowest. * The edge has the thinnest coating (practically none) so that it cools quite quickly * The clay is dried and the sword is heated hot enough that the metal turns into austenite, a crystalline form of steel stable at high temperatures. * When quenched in water, the front edge turns into martensite (the hardest form of steel) and expands about 4%. This is OK because the back of the sword is still quite hot and soft. Martensite is only meta-stable, by the way, and forms when austenite is cooled so quickly that the atoms can't shift around fast enough to reach the form stable at lower temperatures. When you temper martensite, some of it transforms to that lower temperature form. * As the sword continues to cool in the water, the steel continues to transforms towards the back of the sword. As it transforms, it expands. At some point (around the middle), the steel no longer transforms into martensite and changes, instead, into the stable lower temperature form: pearlite (layered ferrite and cementite, IIRC). Pealite is softer and tougher than martensite. The layered structure is really good at stopping cracks from getting larger. * As the sword cools further, the heat from the back edge of the sword tempers the martensite at the front edge, making it tougher (and a little softer, but not much). * Since the leading edge of the sword has already cooled and hardened, it's put into compression as the back edge cools and contracts. (thermal expansion in reverse...) * Everything cools all the way down and the sword can be removed from the water. The complicated heat treatment (and it's definitely nerve-wracking to do, even with a cheap knife blank) causes the samurai sword features: * The blade is curved because the front edge expands and the back doesn't. * The martensite near the front edge etches differently from the pearlite in the blade's back after it's polished, so you get the characteristic line. In fact, if you pattern the clay, you can get a wavy edge, peaks, etc. that match the thickness of the clay. * The front is really, really hard, but the compressive stress created as the sword cools keeps cracks from getting larger, effectively making the sword much tougher. * The back is relatively soft and tough, which is what you'd like when chopping people. There are further variations -- the best swords use wrought iron for the bulk of the blade, which results in a softer and tougher "spine." Also, the traditional iron sand, only available now to the finest blade smiths, has a very fine dispersion of titanium dioxide (IIRC) particles which also help stop cracks from propagating through the hard, brittle edge. Finally, repeated folding of the blade material serves to break up slag and other impurities as well as refining the grains. All of this, figured out over centuries by trial and error, result in a darned impressive weapon. Ken Meltsner ------- Date: Fri, 12 Oct 2007 10:53:49 -0800 From: "Phil Koontz" Subject: Re: [OldTools] Super secrets of samurai swords... Hi Galoots-- I just wanted to thank Ken Meltsner for this gripping account of highly specialized differential heat treating. I really love this stuff. When I started on the hobby of iron working, heat treating seemed pretty simple, but the more I learn about it, the less I know. It is a deep, deep subject. PK Enjoyiing a beautiful snowy day, with ice running on the river. ------- Date: Wed, 9 Jan 2008 09:14:06 -0900 From: "Phil Koontz" Subject: Re: [OldTools] re: playin' with fire >Phil: >I am rehabbing a coal forge right now, but have not used is. Is it a good >substitute for the gas in a can models? Any special trick to hardening >and tempering on a coal forge that make it harder than with a torch? Joe Responding to Joe Sullivan's most pertinent digression about coal forges-- Good on ya, Joe. Coal both opens up a lot of possibilities and introduces some minor complications. You will find that there is a lot to learn about fire management with coal, and that it really helps to have a mentor. Fortunately, they are easily available. Look around for your local blacksmith's association--it's like finding a group of local galoots that like to play with fire, and they are everywhere. I took two sets of lessons from local associations, and would do it again in a minute. Regarding fire management, let me introduce a few principles-- Lighting the fire. Start with three full sheets of newspaper or the equivalent in wood shavings, kindling or such. Llight it and start cranking the air slowly. Sprinkle fresh coal or coke over the developing fire, shoving it around the edges and maintaining an airway up through the middle. Easier than it sounds. Coking. Like burning wood, you need to let the coal burn down so you have glowing coals and not so much flames and smoke. Thi