Heat Treating with a coal forge?

kvehikite

kvehikite

Joined
Jan 8, 2015
Messages
202
Hello everyone. I am new to the forum. Fact is I'm not "new" I just have never joined and or posted anything before today. I have however visited and read a lot. I have a lot of respect for the hard earned knowledge that is openly shared. I feel like an apprentice when I read through the posts. I learn several things everytime I visit here. I've been making knives for about four months now and really feel that I've tapped into something that I will do for the rest of my life. I may never be able to make a living doing it, but I am in love with the process of making a sharp thing out of an none sharp thing.

I have one question to add. If this has been answered, please direct me to the answer. I have an old hand crank coal forge. This is what I use to heat treat my knives. I fire up the forge, place a 16 in. 2x2 square tube in the heat and bury it with coal and crank away. This system does a great job of getting steel up to critical and I seem to be able to keep it up at that temp (granted I'm judging by color and a magnet) and a little higher with the addition of a propane torch fired into the front of the tube. It heats evenly and from my limited experince seems to do the job.

Now for the question. Is this a reliable way to heat treat or should I consider moving toward a kiln? Is there something I could add to the process to make it better? I like to tinker and experiment, so I'm open to any ideas. I don't want to farm out any of what I do to anyone else and I like doing things this way, but I also want to produce quality knives. Thanks for your time.
 
Welcome to Shop Talk.

It may be a workable system....but that does not guarantee it is reliable. Most likely it is just barely doing the job.

A kiln would allow exact HT and HT of many other steels than simple carbon. IMHO, a kiln is a necessity if you want to do HT properly and fully. Most folks go, "Holy cow!, I never realized how poor my HT was until I started using a HT oven." If you plan on selling knives someday, a kiln is absolutely necessary.
 
If it's "just barley doing the job", which I don't dispute, is it the lack of control or is it that it's not reaching a high enough temperature? I realize that 1095 and 5160 both require a soak to fully transform. Would 1084 be a safer bet or is the kiln just the best answer? By the way here is some blades I was able to knock out. Thanks for your time.
10410106_373914586117513_6553399431100088140_n.jpg
10406401_373914616117510_7447849219743706013_n.jpg
 
1084 is the eutectoid steel. It needs no soak and with no extra carbon, carbides aren't an issue. That makes it the simplest steel to HT. If doing a "backyard" HT or any HT with no real control over the heat source, 1084 would be the best choice.
 
It is difficult to maintain a uniform and precise temperature in a coal forge. Near critical probably not better than +/- 25 F across the blade, and as the temperature increases so will that value. I remember reading somewhere that estimating temperature/color relationship (by an experienced blacksmith) could be off by 50-100 F. A well calibrated kiln will allow the precision and accuracy and uniformity to improve by an order of magnitude. Also, a programmable kiln will allow you to accomplish other tasks while the blade is being treated.
 
I definitely recommend a kiln for the heat-treating aspect of knife making. While you're obviously turning out a very nice product, and kudos to you for that, the issue is that you just can't know what you're actually doing in the open forge.

As nice as your knives are, and I really do like your work, imagine how much more comforting it would be to know that you hit all the numbers square on the head.

And, it's nice to be able to do something else while the blades are being heated up. Especially if that something else involves a la-z-boy and some cold beer. :)
 
That's why I asked. I want to be able to stand behind what I make. I see that a kiln (controled heat treat) would knock out one of the variables that might lead to faliure.
 
You must log in or register to reply here.
Back
Top