Stuart Davenport Knives
Knifemaker / Craftsman / Service Provider
- Joined
- Feb 7, 2022
- Messages
- 446
Larrin Thomas with Knife Steel Nerds has put out a new article and video on the different options for keeping scale and decarb at bay. I was surprised it hasn't been posted here yet, but hopefully it will be soon.
I have only had experience with ATP-641 and of course 309 SS foil. For stainless steels, I have come to the conclusion that SS foil is the way to go, and I believe Larrin came to the same conclusion.
For carbon steels, during normalizing/cycling/annealing, SS foil is probably the best way to go, as you can leave the blade in the same packet during all of those heat operations. For austenitizing and then oil/water quench, for me ATP-641 is absolutely the best route to take.
Application of ATP-641 is key, and sometimes too thick of a coating will cause the steel to not harden as expected. This is my method, and it has worked extremely well for me in my shop. I shake the ATP-641 vigorously in the can it comes in. After opening, I stir it with a spoon or the tip of the knife, making sure that the stuff that has settled and collected at the bottom of the container is stirred well into the solution. I take the tip of the knife and dip it in the can all the way to bottom, pull it out, and using my wife's toothbrush, I gently brush what is on the tip (about 3" worth, depending on how low you are it may just be 1" or less) up to the plunge grind and onto the tang, about halfway up the tang. Just kidding on my wife's toothbrush, but I use an old toothbrush. A foam paintbrush might be the ideal applicator, come to think of it.
After the coat is even and THIN, I use my wife's hair dryer (not kidding this time), and after a couple of minutes it is dry to the touch, and you can see the gray color become lighter in shade as it dries. The coating always blows off during the quench. Always. The key is the coating has to be thin. If it's too thick, apparently some are having issues getting good hardness readings. I try to get it very thin, always have excellent results.
I do not trust any coating to 100% negate decarb, so especially on the edge itself, I will grind a few thousandths off under flood of water, and I'm quick about it as well, not to allow any heat build up.
Pretty simple operation, and I hope this helps someone!
I have only had experience with ATP-641 and of course 309 SS foil. For stainless steels, I have come to the conclusion that SS foil is the way to go, and I believe Larrin came to the same conclusion.
For carbon steels, during normalizing/cycling/annealing, SS foil is probably the best way to go, as you can leave the blade in the same packet during all of those heat operations. For austenitizing and then oil/water quench, for me ATP-641 is absolutely the best route to take.
Application of ATP-641 is key, and sometimes too thick of a coating will cause the steel to not harden as expected. This is my method, and it has worked extremely well for me in my shop. I shake the ATP-641 vigorously in the can it comes in. After opening, I stir it with a spoon or the tip of the knife, making sure that the stuff that has settled and collected at the bottom of the container is stirred well into the solution. I take the tip of the knife and dip it in the can all the way to bottom, pull it out, and using my wife's toothbrush, I gently brush what is on the tip (about 3" worth, depending on how low you are it may just be 1" or less) up to the plunge grind and onto the tang, about halfway up the tang. Just kidding on my wife's toothbrush, but I use an old toothbrush. A foam paintbrush might be the ideal applicator, come to think of it.
After the coat is even and THIN, I use my wife's hair dryer (not kidding this time), and after a couple of minutes it is dry to the touch, and you can see the gray color become lighter in shade as it dries. The coating always blows off during the quench. Always. The key is the coating has to be thin. If it's too thick, apparently some are having issues getting good hardness readings. I try to get it very thin, always have excellent results.
I do not trust any coating to 100% negate decarb, so especially on the edge itself, I will grind a few thousandths off under flood of water, and I'm quick about it as well, not to allow any heat build up.
Pretty simple operation, and I hope this helps someone!
