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Coyote_killer2013
10-25-2010, 09:36 AM
Hi I'm new here love the forums so far. I had a question about quenching. If you heat just the edge of the blade with a cutting torch and quench the blade just on the edge not getting hardly any on the spine(maybe some on the tip) how do you temper the blade??? Or do you not even temper the blade??? Thanks

Justin King
10-25-2010, 09:39 AM
I would temper in the normal fashion using an oven.

BRad704
10-25-2010, 09:48 AM
Won't that leave the spine vulnerable to scratching and scuffing? Or does the tempering help that?

Coyote_killer2013
10-25-2010, 11:10 AM
I would temper in the normal fashion using an oven. How long for and how hot??? Thanks

busted knuckles
10-25-2010, 11:21 AM
It depends on the steel but any thing you might quench in the way you described can be tempered or drawn at 350. 350 is an OK temp to draw at unless you are using some highly alloyed steels.
You can do some research on the internet about the steel you're using and find out more about it. Knowledge is power!

busted knuckles
10-25-2010, 11:43 AM
Oh yea, by the way, the whole knife is vulnerable to scratching. while quenching steel does make it harder it doesn't make it resistant to scratches, as many of us can sadly attest to.
the reason you would quench a blade in the fashion you described is so that the knife will be tougher, more resistant to breaking under heavy use because the edge is fully hardened but the spine is maybe only spring hardened.
as far as draw time, it's recommended to draw some "simple" steels for no less than an hour at temp. other steels require two hour minimum soak twice, some three times.
If this seems complicated, it's not. if you keep with this and do your research, you will understand. every steel is treated differently, and many knife makers treat the same steel differently. while there are standard heat treating procedures for each steel, it's almost like a recipe for bread, every baker uses flower and yeast but in different quantities. the result is bread but ever bakers bread is different.
Do you know what kind of steel you're using? if so, let us know.

Doug Lester
10-25-2010, 12:40 PM
You have to understand what happens when you heat treat a blade. What you are doing with your torch is called differential hardening. Just be sure that the part of the blade that you want to hardened is heated evenly to non-magnetic and soaked for about a minute without overheating, which will increase the grain size. Then immediately quench the blade. What this does is change the form of the iron crystals, which are the matrix of steel, faster than the carbon in the irom cystals can escape. Iron crystals in the "cool" phase with carbon molecules trapped in them is called martensite and it is the stress put on the atomic bonds between the iron atoms that gives this form of steel it's hardness, though there are other things that contribute to hardness such as carbides. As quenched, steel with the carbon level that we use for knifemaking have iron crystal under so much stress from the carbon atoms trapped in them that they are brittle and prone to breakage. To reduce this stress some of the carbon must be allowed to escape the iron crystals. That is what is happening when we temper blades; the heat of tempering allows the carbon atoms to go out of solution from the iron crystals reducing the stress on the atomic bonds between the iron atoms. The softer steel in the spine area of the blade that was not heated to non-magnetic before quenching does not have any martensite in it's structure and is not relevant because it does not effect the part of the blade that contains martensetic steel. The hardened areas of the blade must be tempered.

You also wouldn't want the steel to be totally scratch resistant because then you would have a very hard time grinding it or putting an edge on it. It would also probably be so hard as to be brittle.

Doug Lester

Coyote_killer2013
10-25-2010, 01:23 PM
WOW....not sure what kind of steel it is, my uncle gave it to me.

Justin King
10-25-2010, 02:03 PM
Usual tempering cycles are between 300F and 500F and are 2 hrs long. Two cycles with a cool down to room temp. in between is typical. Some highly alloyed steels require higher temps and 3 cycles.

Doug Lester
10-25-2010, 03:20 PM
Ok, next problem. We don't even know if this steel can be hardened; it could be structural steel. If you have a small piece of it, heat it up to non-magnetic, quench it in water, and strike it with a hammer. It should shatter if it has enough carbon in it to harden sufficiently to make a knife blade. Do yourself a favor and go down to "Knifemaker's Shop Talk" and click on "A Sermon to Newbies" and there is a list of reference material there that would be good for you to get. You really sound like you could use some serious book learning. No one on this board was able to just pick up a piece of steel and start making knives without putting some study into it. As a matter of fact, this art is pretty much a constant study.

Doug Lester

Coyote_killer2013
10-25-2010, 05:40 PM
Thanks for the advice.

Coyote_killer2013
10-25-2010, 05:55 PM
Sorry to keep asking questions, but what are the best oils to quench in???

Fred Rowe
10-25-2010, 06:53 PM
You have to know what steel you used. Period. If you don't know, you are guessing. If you are guessing, there is no way to set up a heat treating schedule for that particular steel. If you are forging the steel you are "heat treating" throughout the forging process; not just the actual quenching.

I suggest doing some reading on steel fundamentals.

Fred

Coyote_killer2013
10-25-2010, 07:19 PM
If its any help all I know about the blade is that it was on a delimbing machine as a tooth I guess. But it was very precise and hadn't been chipped in any way. Maybe that will help maybe not.

Doug Lester
10-25-2010, 08:36 PM
As Fred alluded, mystery metal is a real crap shoot. First find out if it is hardenable. Second you will have to experiment with every new piece to get the heat treatment right. My suggestion would be to harden and then temper at 375 degrees, grind a course edge into it and test it. One way is to do a brass rod test. To do that take about a 1/4" brass rod and secure it horizontally on something solid. The lay the blade flat on it then raise the spint untill the edge is resting on the rod and press down until the edge deflects slightly and release the pressure. If the edge of the blade stays bent then you will have to reharden it and retemper 25 degrees lower. If the blade chips out then grind the edge even again and retemper at 25 degrees higher. What you are looking for is the edge to fles and return to normal without chipping.

Another way is to cut some soft steel wire with it. Place the edge on some soft steel wire, like bailing wire, and strike the spine with a mallet. The edge should cut or at least cut into the wire without chipping or rolling over. If it does, proceed as above.

If you start out with a known steel then some of us who have used it will be happy to give you a starting point in heat treating, though you should test the edge on any knife that you make. Once you know how a given steel from a given supplier works you can use that data for each knife that you make from it. Admiral Steel will sell in small lots, Kelly Cupples, who is listed at Ellis Custom Knife Works, is also a good supplier. The New Jersey Steel Baron is a third source of blade steel.

Doug Lester

JDW
10-31-2010, 06:54 AM
Coyote_killer2013, do some research as Doug suggested, and then get some known steel, and anyone on here will be glad to help you out. It sounds like you intend to heat your blade with a torch, so I would suggest 1080 or 1084, as they require a simple heat treat that can be done with a torch. As to what oils to use, you can use veggie oil, canola oil, vet grade minerial oil, with 1080-1084 and have good results, some steels these will not work on.
Dale

Kevin R. Cashen
10-31-2010, 07:38 AM
I think it is worthwhile to explain the precarious position involved in advising heat treat without supporting data. When folks hesitate to give heat treating recipes for mystery steel they may seem to be coming off as elitist or thick headed about only using pretty, new bought steel, I know I have had such epithets and a few others tossed at me. But the real motivation (at least for myself) is the desire to not only see people succeed but we would really hate to see somebody destroy something that they worked really hard on with the wrong method based on a wild guess on our part. I think I am reading things right when I sense that in this thread.

Most industrial applications these days, such as the delimbing apparatus you describe, can have very complex alloys to handle the task, so the heating method as well as the quench could be fairly particular. The safest bet is to start testing a sample of the steel, heat and quench. Start with just air cooling and then run a file over it. Next move to a slow oil quench and do the same before moving on to the next fastest oil. Starting with water based quenches on any modern alloy will be a recipe for disaster.

The testing for homing in on the method that works for an unknown steel can get very involved, I think these gentlemen are trying to save you much of that trouble for the next blade. When you have the chemistry for the steel, you can dispense with all the testing and troubleshooting and get right to making the knife.

Doug Lester
10-31-2010, 01:29 PM
Kevin, you said it better than I did in three attempts.

Doug Lester

JDW
11-02-2010, 06:07 PM
Very well put Kevin, you sense my response correctly, I hope Coyote_killer2013 does too.
Dale

Coyote_killer2013
11-03-2010, 09:13 PM
Alright next time I'll try to get a known metal. Thanks

BRad704
11-07-2010, 09:07 AM
This is off-topic, but Coyote Killer... are you also into SKS rifles? I just noticed the same username over on Survivors SKS boards...