2 knifemaking questions

A

Adamantium

Joined
Oct 3, 1998
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Hi, I've got 2 questions(Actually, there are several questions, but in 2 catagories) I need to ask.

One is about heat treating. I've heard a handful of times that doing more than one quench(Bring the knife up to its critical temp. then cooling it down by brine, oil, air etc.) will bring grain size down. And make the knife tougher. My questions about this is, 1. Does it only work for simple carbon steels? I've heard of doing this for 52100 and O1, but I also think I heard at Blade that this will improve 440C also. and 2. Is each quench after the first done the exact same? Do you just wait until it is room temp then start heating it up again, or do you let it sit for a while. Do you use a less critical quenching fluid because there is already lots of stress in the knife?

And my second question is about heat build up while you are grinding steels. Which steels are affected my this? Most high-end stainless steels are supposedly ruined if you haet them up too much while grinding. I'm wondering if that applies to A2, D2 and 440C.

Thanks

Sincerely,
Adam

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Self improvement is a hobby of mine :).

 
I've been told by several folks taht the level of heat generated when grinding will not damage any steels before heat-treatment. When grinding after heat-treatment, make sure you go fairly slowly and keep the piece well-cooled. makers like Frank Centofant who do all their grinding after hardening the steel use special grinders with water bath systems for this. For a more standard approach, do as much grinding as possible before heat-treatment and then go easy after. You probably want to do work bare-handed after heat-treatment because this lets you judge the temp better and gives you an "automatic" reason to stop if it gets too much (you probably want to do all your grinding bare-handed for better feel, anyhow). Also watch for colors - after heat-treatment you should not be heating the steel enough to produce any discoloration. If you get a little, cool immediately and be sure to grind that area away - slowly this time.

Well, that's how I do it, anyway. If someone says I'm wrong we'll both learn something!

-Drew
 
Like Cord said, before heat treatment, heat buildup is only critical to unprotected fingertips. Word has it that when Bob Engnath ground blades they were red and the wooden push stick he used sometimes caught fire.

That being said, there are some steels that will work harden if they get too hot. I don't know much about this but I think Cruwear is one of these work-hardening steels.

 
Hi Adam,

I agree with Corduroy about Finish grinding bare handed but if you do your profiling and rough bevel grinding agressivley, as I do, you should wear some fairly heavy leather work gloves. One time of using heavy pressure to a 36 grit belt and accidently getting a finger into it will make a believer of you forever. Does this sound like the voice of experience? When finish grinding you should use a much lighter touch and really fresh sharp belts.

As far as multiple quench goes, it has a significant effect on the simpler carbon steels up to and including the third quench . You should just let the blades cool in oil until they are slightly uncomfortable to hold, about 150 F, then clean off and back into the fire. Again, after the third quench cool to about 150F clean and into the oven for temper. I temper 5160 at 425 F the first time (2hrs) then 400 F then 375 F (2 hours each time. Always allow slow air cool to room temperature when tempering. This will generate a tough, edge holding blade at about 58RC.

I dont believe the multiple quench system is beneficial to air hardening or high alloy steels. One way to find out for sure would be to try it on several and test them. However for testing I would recommend wearing a leather apron, gloves and face shield. When steel breaks in that kind of testing it can fly like shrapnel.

Hope this helps....GARY B
 
Thanks guy. Yeah, I do most of my grinding before heat treat. As for how high Bob Engnath got his blades, Wow. I really wish I had gotten into knives years ago, before he passed away. I would of loved to meet him at least once.

Sincerely,
Adam

Salmon Creek Knife Works

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Self improvement is a hobby of mine :).

 
I have not heard of air hardening steels gaining anything from a multiple quench. Some will benefit from a multiple temper, 2 times for D-2 and 440C, 3 times for ATS-34. It seems to help both stress relieve the blade and add a bit of toughness. Ditto for adding a cryo cycle.

I have been told by some folks that you should not overheat ATS-34 while grinding, but I haven't seen a problem with any air hardening steel. You're not going to get it anywhere near as hot as the temperatures generated in heat treating. As noted, Bob Engnath used to grind 440C and ATS-34 and literally turn it red hot while profiling and grinding the blade bevels.

One thing to watch is working some of the air hardening steels like D-2 with dull abrasives, they don't so much harden from the heat, as they do work harden on the surface being ground. Its a real pain to continue grinding until you cut through the surface that has been work hardened.

madpoet
 
Concerning temperature build-up after heat treatment: It should be avoided at all costs! Remember, you only need to reach a temperature that is higher than the temperature at which the blade was tempered in order to change the microstructure. Many guys temper tool and stainless steels in the 400F range, and, remember, when you burn your finger, you're feeling the heat that's come through the blade, not the heat at the interface between the belt and the steel. You can reach 400F real quick, and never know it.

As to heating blades red hot before heat treatment, you can do it. I won't. You started with nice, annealed steel that has a microstructure set up for proper reaponse during heat treatment. Why screw it up by being in a big hurry to grind that blade!!
You guys can quote Egnath, and Loveless, and whoever you want, and, I'll still prefer keeping the blade cool. Just my 2 cents

RJ Martin
 
RJ,
Thanks for the clarification. I meant to say that I don't think that the temp is as critical 'before' heat treating. Afterwards, I make sure not to get any steel so warm that its going to discolor, or break the barrier temp at which it was tempered. The easiest way to do that is to work with your bare fingers, and either cool the blade, or quit working it when it gets too warm to be comfortable to hold.

As for the Engnath quote, I just hope I live long enough to hear someone say, "well, I know RJ, and darrel, and a bunch of guys that were pretty famous used to do that back in the dark ages, but I feel better doing it my own way......"

madpoet


 
I don't know about all steels but I do know that Cruwear (or Vascowear) will harden if it is gotten too hot while grinding. I have rendered it useless by getting it too hot. When working with Cruwear, I recommend working it with a bucket of water nearby. I grind it without gloves so if it is too hot to hold, it gets dunked. This, among other reasons, is why this steel takes longer to work with. I don't know how 3V is regarding this, maybe Ed Schott can comment on it.

CLWilkins
 
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