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  #11  
Old 10-25-2007, 12:22 PM
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For small hobby things I used old vegetable oil from a deep fryer.
The O1 hardens about 1500º F you need to also compensate for the three seconds it takes to get it from the oven to the oil, so may be bring it up to 1650º F. for large parts you probably need to let the heat soak into the metal.

I haven't had it catch fire, but you never know. Assume it will and take all the safety precautions for OIL FIRES.

This site looks good for hardening temps.
http://www.buffaloprecision.com/data..._sheets_cp.htm
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  #12  
Old 10-26-2007, 07:49 PM
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Quote:
what oil do you guys use
Any oil with a high flash temp will work ... Mobil 1 synthetic is cheap & easy to find at Wally World. Cheap is important, as you'll want at least one gallon for tiny parts, five to ten gallons for larger parts. The reason for the large quantity is that repeated quenchings will quickly bring the oil to near the flash point ... go above the FP for a real lesson in pyrotechnics

My favorite oil? Peanut oil has a FP over 600°F, and reminds me of frying chicken or frying turkey.
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  #13  
Old 10-29-2007, 08:56 PM
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In that class I took, the "boss" brought in a metal 5 gallon bucket of straight 30 wt. non-det. He said that when he was working in the foundry in a large mine, they used a half of a 55 gal. drum - cut around the circumfrence, with a rack that held the pick heads so that the ends were about six or so inches in the oil; they'd finish dawing one, put it back in the fire for a few minutes, then set it down into that rack, and go on with the next one.
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  #14  
Old 10-29-2007, 11:16 PM
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Ok, I have watched & waited for several days; being the Curmudgeon, I will go ahead with this report - the redneck guide to hardening & tempering.

I have one lone occasion in my life where I needed to to anneal a piece of steel so I could shape it, then harden it and come out the other side with a useable blade. This was for a compound molding plane. I had a "commission" to produce a hand-made trophy/ribbon case for a show horse named Henry and I wanted some unique molding for the crown.
Well, I had bought every plane I could locate in this little burg including a sack of wooden molding planes; the best profile had no cutter.
I had no experience and really, no suitable tools. At the time I also had no internet so I went to the library. One English text became my guide to annealing and hardening.
Since I had no forge I used my homemade barrel BBQ grill and a vacuum cleaner. Since I doubted that I could tell the difference between "straw" and "yellow", I followed the alternate method for dummies.

When the steel heated past orange I began to test it against a magnet on a stick (copper tubing); when magnet lost interest in the hot steel, I called it good, socked it into a bucket of ashes & left it 24 hours. After I had sawed, filed and Dremel-ed the profile into the new cutter, I repeated the process until the magnet reject the hot steel, quenched in a bucket of burnt motor oil & spent about a day finishing & honing the new blade.

I guess the simple approach worked well enough. I used it to make about a dozen feet of imperfect walnut molding, culled it down to a nice crown about 5 feet total length & that was that. I hope Henry & Annette are still pleased with his trophy case because I spent 3 years learning to collect, repair, hone & use the hand tools needed, and to make the cabinet.
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  #15  
Old 11-04-2007, 09:01 PM
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Its possible that he didn't forge it at a high enough temp. Some steels will tend to form cracks even at a low red heat if you're trying to do much more than straighten them.

As far as the hardening and tempering process, I would agree that oil may be better for that particular steel.
I also would prefer to quench and temper with seperate heats. You can generally guess the right temp to austenize the steel with a magnet as mentioned by cutter. But there is still no sure fire way of knowing that you have brought the steel back below the transmformation temperature when you try to interupt the quench while part of the peice is still hot enough to temper.
If you look at a TTT curve you can see that there are a wide range of possible outcomes depending on how much and how fast you cool the piece. While an interrupted quench will probably miss the pearlite nose pretty consistently, you don't know if you're forming bainite, or martensite. And you would have to follow very consistent times from one part to the next to get the same results.
So I like to fully cool the part the first time, even if it isn't a full quench. Then temper. For the chisel, you can heat the striking end with a torch, or hold it against a hot block of steel and watch the colors creep up to the tip. When it reaches a straw color, quench and you're good. If I want a uniform hardness I would temper in an oven.
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  #16  
Old 11-05-2007, 02:25 AM
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Matt, you seem to have a pretty good amount of knowledge on this subject so, tell me if I'm full of crap. I was always told that, when you quench the part, it's important to move it around in the quenching medium or you'll stifle the quenching action. In other words the oil will get too hot around the part if you hold it in one place so, swish the part around. In the toolroom, we had a wire mesh basket with handles that went down into the oil. You would heat your part, place it in the basket and move the basket up and down in the oil 10 times or whatever, to get that heat away from the part as quick as possible. Then, when the part is cool, shine it up with emery cloth and get ready to do your tempering. Sound right?

Dave
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  #17  
Old 11-05-2007, 06:30 AM
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Sounds good to me Dave
The reason for moving the part around is to agitate the quench material. As the hot part enters the quench, it generally causes it to boil at first and lots of bubbles form. Moving the part around helps prevent the bubbles from forming an envelope around the part and insulating it from the quench.You wouldn't expect it to make that big of a difference but some steels have a very narrow window to work in.

Thats why we choose quenching mediums with a high vaporization point as well as flashpoint. Instead of quenching in pure water, alot of folks like to use brine. The easier the medium vaporizes, the more that envelope tries to form.
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  #18  
Old 11-13-2007, 09:27 PM
Clay Walters Clay Walters is offline
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Interesting thread.

I always heard use the oil from your crankcase (burnt oil) since the dirty oil meant a high carbon content and enhanced the temper.

Don't know and never tried it myself. But I do know the few times I forged a chisel I heated until the tip edge was white hot and moved it as fast as I could to a can of ice cold water. Always seemed to work.

CW
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  #19  
Old 11-13-2007, 11:29 PM
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Quote:
Originally Posted by Clay Walters View Post
Interesting thread.

I always heard use the oil from your crankcase (burnt oil) since the dirty oil meant a high carbon content and enhanced the temper.

Don't know and never tried it myself. But I do know the few times I forged a chisel I heated until the tip edge was white hot and moved it as fast as I could to a can of ice cold water. Always seemed to work.

CW
You like to live on the edge don't you ?
I don't think my luck will ever be good enough to use ice cold water and not hear the dreaded "ping". I'm not real practiced with water quenches but the few times I did it, warm water was used. With oil, you generally heat it up to at least 100 degrees to improve the viscosity and help speed up the quench. Most of the reading I've done is on oil quenching though, maybe there is something to cold water.


Also, heating by color is subjective. Everyone's eye is different, and it will also look different depending on the amount of ambient light. So you might have been right at the right temperature with "white hot". Its important to not overheat the steel though as this promotes grain growth, which will make the part more prone to breaking and can cause problems with wear resistance and other things. You only need to heat the steel until the point that austenite forms in a solid solution. Its a little easier to undestand whats going on if you look at an iron carbon phase diagram ( check out this page: http://www.ul.ie/~walshem/fyp/iron%2...%20diagram.htm ) Keep in mind that the tool steels we deal with generally have less then 1% carbon, so you are dealing with the far left hand side of the chart.
The trick, is that steel is non magnetic when it is in the austenitic form. So if you heat the steel until it no longer attracts a magnet, you know you are in the right range for transformation. Then you just need to experiment with how long to hold it at that temperature for the transformation to take place completely. With small parts, using simple tool steels its less than a minute.

I do use used crankcase oil when I heat treat the knives I make, but only because I have it on hand and I'm cheap. I don't think that it will change the carbon content of the steel any, at least not beyond the surface which usually gets ground off. I don't know alot about that subject, but from what I've read on early steel making (read about blister steel, if you're interested) you have to have hold the steel/iron in a carbon rich environment at a very high temperature for a long time for any carbon to be picked up.
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  #20  
Old 11-18-2007, 11:07 PM
1vegoil 1vegoil is offline
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Several of the last posters in My opinion have been correct on treating the steel... I heat treat steel daily..and heat treating is a several step process starting with the shapeing...any piece of high carbon steel that is to be shaped into a tool or any shape must first be properly annealed...depending on the tool the shape and the material annealing can be a simple step simple carbon steels like 1080 1095 1045 and some semi complex steels 5160 9260 etc can be heated to a NON MAGNETIC state as "CUTTER "suggested...this when all structures are in solution meaning seperated...then plunge that piece into a box filled with vermicullite or a simular insulation to slow the cooling process... Normalising is very simular except that it is a step to neutralise any preset streeses from machining or forgeing to shape a piece of steel the difference is that normealising is done in room temp air....MOST simple steels that WE use for tools will go into solution at NON MAGNETIC (all perlite and ferrite in solution) and can be quenched into simple oils mineral oil trans fluid etc hetaing those oils to 160 degrees helps lower the stress on steel... the mentioned moving of piece in oil is true, an envelope of air does exist around the HOT piece...when the oils ceases to be real active simply leave the piece in the oil until room temp or over night....IT NOW IS HARD(all perlite and ferrite coverted to martinsite) like glass(test it with a good file it should not be easily filed) it will even shatter if used as a tool....Tempering is the next step and colors are one way but available light, metal finish , individual eye, all have a bearing on that so as a knife 450-500 degrees or straw color as a tool 675-775 degrees a purple or dark blue color and stop with room temp oil "less stress" or water etc some or all of the tempering time and stopping, will be from trial and error for your tool ..unless you have a "paragon oven" and exact spec's for the exact steel you are working with....hope this helps.. I can give you many urls for more resource if needed...Jeff www, swainsspring.com

Last edited by 1vegoil; 11-18-2007 at 11:15 PM.
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