Tempering ?'s

K

kbtube

Joined
Sep 7, 2008
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1
Hey everbody,
My name is Kyle I'm a newbie. I have been reading posts on this forum for months now. there is so much combined knowledge in here sometimes its overwhelming. Just wanted to thank everyone that contributes here. So cut to the chase I'm in the process of making my first knife out of a file. The file is Oberg brand from Sweden. I have already hardened it heated to non magnetic and oil Quenched. My question is in the tempering process. Twice for two hours at 400 deg. ? Quench after that? Let cool slowly in the air? In vermiculite ? Any information will be of great help. thanks Kyle
 
Check and make sure it got hard first. It should at least skate a file. Then temper at 400 for two hours, letting it cool to ambient temp in between tempers. No more quenching. Vermiculite, etc. is for annealing the file before the initial grinding. FWIW, the "generic" heat treat method (I use it as well, so nothing intended) may or may not produce a great blade, but often produces good blades. We're not likely to get the steel's top performance using backyard methods, but sometimes that's OK.
 
Hello Kyle,

Welcome to Bladeforums. Looks like you have received some good advice above. I see you live in San Diego as well. If you want to talk shop some time, send me an e-mail. You can find it by going to my personal profile then clicking on contacts.

Eric
 
Tempering should be done immediately after hardening. To wait is to risk cracking. 400 F is a good start , for two hours. Generally one temper for simple steels ,two for more complex , and three for the very complex steels. One or two for a file.After tempering cool it anyway you want as the tempering is done at temperature ,cooling doesn't change anything.
 
Sorry to bust in, but what's the deal with tempering with a torch?

Could you, say, put some insulating material around the edge area, or quench the edge in something periodically, while heating up the spine with a torch? Would this be a good way to achieve a soft spine and a hard edge?
I'm making a largish knife from a pretty thick ass file. Big bush knife. Probably take me a year....

I understand one should look for a 'wheat' color in order to determine that the knife is properly hardened at the edge. Is that right?

If I were to harden a file knife in a fire, would it make sense to point the edge up and the spine down toward the ground in order to get even heat on both sides of the knife? Does it matter? Does it matter how long it cooks in there, or do you quench it when it's cherry red, and that's that?

I read that the quenching fluid should be warm, around 200 degrees and that the blade should go in vertically, tip first and be oscillated vertically in order to avoid warpage.

I watched Myth Busters last night, and learnt that coals burn at around 1400 degrees, which my research has led me to believe is about the right temperature for annealing and hardening simple steel alloys. Make sense?

Again, don't mean to horn in here, but I saw the holeshot and took it. Saves threadspace:)>
If anyone could corroborate any of the bs I just spewed, I'll be surprised:D
And thankful for advice and admonishments.
 
Quenching oil should be 130-140 F. I think you should read the tutorials on heat treating first before the questions.
 
What Mete stated is sage advice. Take a look at the tutorials that Dan gathered and posted.

To address the annealing process, the steel is heated to non-magnetic then slowly cooled. This can be done by placing it in the (gas) forge and turning it off, preferably covering the ends with insul wool or whatnot. One other method is to place the blade entirely in vermiculite, agricultural lime, or hard wood ashes and let it cool overnight. One trick here is to heat a larger piece of steel or pipe and place it in with it so it will cool even more slowly.

Probably the way with the most consistency is that if you have a heat treat oven is to heat the oven to the specific recommened temperature for the steel you are working with. For example, 4140 starts at 1650 degrees and is ramped down at 50 degrees/minute until 1000 degrees is reached. From that point the oven is turned off and allowed cool from there.

Craig
 
Lorien,
The use of a torch to draw the temper on the spine is fine, but it is done after the regular temper cycle.
For instance:
You have a 15N20 (L-6) blade that you want a hard edge, but soft spine. You fully harden it in an oil quench ( should end up about Rc-65). Temper once at 400F, for two hours ( drops to Rc62). Then, put about 1/4" of water in a cookie pan and set the edge in it. Use a small torch on the spine to draw a temper in the straw yellow to light blue range - constantly rocking the edge back and forth to keep the entire edge cool ( Rc 62 edge, Rc 54 spine).

This allows for a fully tempered edge, and a fully softened spine. If you just used a torch to draw the spine, without the first full temper, you would have a brittle edge, and the spine would be a mix of different structures and hardnesses ( it takes longer than two or three minutes to convert the super hard untempered martensite it tempered martensite and pearlite).
Stacy
 
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Thank you very much guys! I'll take that great advice and continue researching the topic. To be honest, my eyes are going a little crossed reading through page after page of computer screen how-tos! Well, I started off a little cross eyed, so I can't blame the computer for that:).

I used to have a site bookmarked that noted which steels are commonly used for various things. I have no idea where that site is, since we replaced our ole computer. And at the risk of asking too obvious a question; could anyone tell me what kind of steel my file might be made from?

Lastly, is it fairly standard procedure to use color as a guide when heat treating steel?

We're so lucky to be able to share information like this so quickly. I probably wouldn't even bother trying to make a knife if the knowledge was not so easy to come by. Or maybe I would. Point is, I really appreciate anyone taking the time to answer my stupid questions.
 
A file can be made out of many things....not all good to make knives from. If yours got hard, then it may be OK, but the metal and HT is a guess, at best.
That has been discussed many times here. My advise is always....When learning ,use a known steel.

Lists of " Steels and Uses" are pretty much useless. Most are quite old and predate modern steel suppliers and parts. Some perfect examples are:
Files listed as being W-1. Some are, some aren't. (Some are 1040 and case hardened.)
Leaf springs 5160???? - I doubt it today.
Saw blades L-6?????? ?- not likely at all.( Most saw blades are useless as knife steel.)

Color is a guide to the trained eye, but is little use to one who has no experience. For the untrained, it can be disastrous. Ambient lighting and personal color perception vary greatly. In a test using skilled smiths, almost none were even close at guessing the temperature of steel by color. Temper colors (Straw?,Yellow?,Light Brown?) are quite confusing....untill it turns blue ( Blue is bad, unless you are making springs. But even blue can be a false color if it is caused by some oil left on the blade before it was tempered. Baked Oil can make a rainbow of colors that mean nothing at all.)

I heard of one chap who heated his blade up to yellow to temper it and it was ruined. Turned out he heated it to yellow heat, or about 2000F, not knowing any better. He had seen a color chart that listed steel colors...unfortunately it was for forging, not tempering.

A kitchen oven is the best starter place for inexpensive tempering. It may not be totally accurate, but it will be close enough.
Stacy
 
Well, the file I annealed in a fire pit is pretty huge and thick. Not the kind you see in your standard hardware store these days. I'm pretty sure that it's old and decent quality, since I got it from a garage sale that was the remnants of this deceased fellow's estate. I'll scrub away at it and see if I can find out anything more about where it came from, but it looks to me to be a pretty good piece of steel.

I've been hacksawing the profile out and it's very time consuming, and I'm going through blades. But I think that has more to do with the thickness, which is at least 12mm, as a file bites into the material pretty easy.

I'm hoping to gradually file a taper from the ricasso, and the only thing holding me back is finishing the profile and buying a another file; this happens to be the file I would have been using to file with:rolleyes:.

The overall length I have planned for this knife will be around 15", and the handle tang is hidden, 3/4 length, with a stepped ferrule and a pin. I have a convex geometry in mind, which I'll be applying without the benefit of power tools.

Ok, so quenching in oil heated to around 140 degrees after 10 or 15 minutes at cherry red/non magnetic. Then let it cool to ambient temperature?
Then one temper cycle for 2 hrs at 400 degrees. Then draw the spine, isolating the edge in water. Then another temper cycle for 2 hrs at 400 degrees.
Each temper cycle should allow the knife to air cool at and to room temperature.

Does it sound like I'm on the right wavelength here?
 
With what you have available, plus lots of elbow grease, that should work (assuming the file is hardenable steel).
Stacy
 
:thumbup::D
copious amounts of elbow grease, in my experience, equates to copious amounts of ibuprofen.
Thanks again for the great advice, fellas!
 
well, shit. After a little sanding, the heart wrenching word was at last readable, and it said 'INDIA'.:o
Oh well, a good friend of mine has offered to not only supply me with some good steel, but also to heat treat it for me. I'll make my knife yet, dammit! And with his help, it will be a good one!
 
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