ATP Anti-Scale in a gas forge

Bill Hubbell

Looking for input-
I am making a new blade for a lock-blade folder that my wife gave me about 30 years ago for an anniversary present. I was stupid enough back then to let a hardware store employee 'sharpen' my knife. He destroyed it, and it's been sitting in my drawer ever since.

I've never done anything with folders.

I have the blade ground close enough for heat treat. It's 1084, a shade over 1/8 thick right now (the ricasso/hinge area). That leaves me .015 to play with after heat treat to get it to the thickness of the old blade.

I'm nervous about loosing too much to scale during heat treat. I was told that coating it with ATP before heating it up would help. I only have my gas forge- no electric. I'm also wondering of I would be better off to heat it with my acetylene torch instead of the forge. -seems like I could be more careful of the thin edges. I don't have a rosebud tip, but thought maybe if I adjust it to be sure it's a carbonizing flame- not too intense, it might work ok. ???
Also thinking it would be harder to read the temp if it's coated, and also wondering why coating it wouldn't alter the quench process. I planned to take it just past non-magnetic, and quench in canola/peanut oil, since that's what I have, and have used before.

So, as you can see, I'm full of questions. Any help or advice will be appreciated. Thx, Bill

Kevin R. Cashen

Super Moderator
Hello Bill,

The anti-scale will be fine. If you have the atmosphere adjusted right, and the time is correct, there should not be enough scaling to make a difference in a gas forge, in fact whenever I teach students to use the gas forge for hardening there is seldom any scale at all. On 1/8" the anti-scale will have little effect on the quench, so I wouldn't worry too much about that. You really should use just the canola if working with vegetable based oils, the peanut oil is one of the worst oils I have worked with, speed wise, so I would just save it for cooking with.

If you are really concerned about the edge, you could build an improvised forge and use a real lump charcoal fire with a tunnel, built from 4 fire bricks, over it. This will allow you to heat the spine first and the caburizing atmosphere will produce a blade very clean of scale, if done right. About the worst thing you can do, if you want to avoid scale, is use a torch. If I could accomplish one thing as a gift to the craft of bladesmithing it may be the elimination of the very concept of austenitizing with a welding torch. With a 6,000°F they were designed to melt steel, not accurately heat it, and any part of your blade that is not covered at that moment with the flame is decarburizing and scaling. A bladesmith that is concerned about tradition uses a forge for heating steel, a bladesmith that is concerned about absolute control, to get the most out of a modern alloy, will use precise digitally controlled heat sources. Neither will use a torch.

Bill Hubbell

Thanks for your input. Kevin. The anti-scale compound came today. I will forget the torch idea, use the ATP anti-scale, heat cautiously in my gas forge up to non-magnetic, and quench in the canola I have (after heating it up).
Then, unless I hear otherwise, I'll do 2 temper cycles at 400 degrees for 2 hours each. I'll follow up here with updates when I get it further along.
Thanks again for your advice!

Bill Hubbell

Wow, where did that year go? I see I've been absent from KD for over a year. Even missed out on the Christmas gift exchange. I got on and looked at an old post and realized that I never sent an 'after shot' ofthis project like I said I would. I've been carrying this off and on for about a year. I am pleased with the end result (flaws and all). And my wife said shes proud of me- not because of how well the knife turned out, but because I said I was pleased with it even though it has some flaws. Anyway, here's what I came up with. Thanks for all the help from all you guys along the way of my 'knifemaking journey'!
PS: the anti-scale compound worked great.