clay temper question...

[manghu67]

when doing a japanese style clay temper, does the clay go on the handle?

does the whole piece, handle and all, go in the forge, or just the blade?

thanks!

 

[RokJok]

Clay goes just on the blade. Only the blade goes in the forge. The wrapped handle gets put on after heat treat and tempering are done. Forge temps would instantaneously combust a handle.

 

[rhrocker]

Manghu, when you say "handle", are you refering to the tang? If so, then yes, the entire thing goes into ythe heat source. You can put clay on the tang, although I don't think that most do, or at least I don't. After the heat treat and tempering, the tang can be drawn back using a torch, keeping the blade submerged in water. Quite heating when the tang is blue. Terry Primos does a different version of this which I think is neat: He holds the blade at the ricasso with his thumb and index finger (ungloved), heats the tang with the torch, and when things start to warm up, he submerges the blade, and his hand in a 5 gal bucket of water, leaving the tang out of the water, till things cool down. This leaves his blade at whatever hardness he heat treated and tempered at, and softens the tang area.

 

[manghu67]

rhrocker: yeah, i meant tang... honestly, i should have known better... now i feel stupid...

the torch draw for the tang is interesting, but clay there and on the spine would get the job done in one...

wouldnt drawing the tang like that create more stress in the steel (you have your edge at one hardness, your spine at another, and your tang at yet another)?

 

[primos]

... wouldnt drawing the tang like that create more stress in the steel (you have your edge at one hardness, your spine at another, and your tang at yet another)?

I just saw this one.

The short answer is "no". Well, a better short answer might be "it depends". Like everything else, there aren't many absolutes.

Having multiple zones of hardness in and of itself would be no problem, or nobody would be doing it. The main thing that will get folks into trouble when using a torch to draw back a zone is not taking the time to do it correctly. That is, getting things too hot too fast.

The colors from the oxides "sort of" tell a story, but it's not necessarily an accurate story. If you take an O/A torch and bring the tang to blue in 10 seconds, you have not accomplished the same thing as say, using a propane torch and slowly and methodically bringing the tang up to blue over a long period of time.

One thing that makes this knifemaking gig difficult for people just starting out is that there are so many different methods and opinions. You will have one maker saying that he does things one way, then someone else will come in and say, "In my experience, that causes [ insert some problem here ]. You have to keep in mind that there are about two million variables, and what works for one guy in his shop, using his equipment, may not fair so well for the next guy.

So, I could occasionally argue in some cases that advice someone gives on these forums has caused me grief in the past, but that only means that it was my experience in my shop, and not that the other guy is wrong. I don't know if that makes sense or not.

The methods that I use now are combinations of methods that I picked up from other makers through the years. What I do is not exactly like anything else I've seen any one maker do. In time, by experimenting with and combining various techniques shown to you by others, and incorporating your own little tweaks learned through trial and error, you will come up with what works for you personally.

Anyway, why the heck am I rambling like this? Too much coffee again today.

Here's a shot of what Robert was talking about.

This is not something I do on every knife. It this case I had done a full quench. I left the tang above the quench line, and because of how quickly the tang lost all color, I figured that I probably had a harder tang than I wanted. I drill my holes after the handle is in place, and nothing is as frustrating as getting part way through the tang and hearing that "s-c-r-e-e-e-c-h" sound. So, after tempering, and testing the blade, I started drawing back the tang and the back of the ricasso.

The reason I hold the blade in my bare hand is so that I am attuned to how much heat is traveling down to the blade. I start at the back of the ricasso with a painting action. I work all the way around the ricasso, and gradually work up the tang. When my thumb and forefinger start to get uncomfortable, I am still a l-o-o-n-g way from being too hot on the blade. I put the blade and my hand in the bucket of cool water, leaving the ricasso and the tang above the water line. This not only keeps the blade cool, it starts forcing the heat up the tang towards the butt. I will see the tang starting to turn blue where I have not yet even touched it with the torch.

When my fingers are cool again, I come up out of the water and continue with the heating. I concentrate mainly on the thicker areas and keep forcing the heat to travel to the thinner areas. I will seldom get the torch past the halfway mark. Once the tang is an even deep blue and the back of the ricasso is peacock (purple), I let the thing cool down completely, then sand the area down to shiny steel and go at it again. I do this three times which seems to be a magic number to knifemakers. When I can drill a test hole in the tang with no cutting fluid, I'm happy.

The steel in this photo is 1084. For steels like 5160 and O1, you really want to make sure that you don't heat too quickly, and definitely don't let the steel get red. You will likely get some air hardening, which is exactly the opposite of what you are trying to achieve.

 

[C L Wilkins]

Mr. Primos,
You have a way with words. That is as thorough an explanation as I have seen.

Craig

 

[RARanney]

You can ramble like this anytime. Information such as this is very hard to come by, and very much appreciated.