Copper Go-Mai

K

Ken H>

Joined
Dec 31, 2011
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I've always been impressed with the copper line in the blade and wanted to try one myself. I did this one with a .070" of 26C3 core, a .030" layer of copper on each side, with a 3/16" of 1075 on each side. After forging and shaping I got this skinner. It's still a bit rough in the ricasso area. It seems the tong hole is popular so I added a bit of paracord with mammoth ivory button.
Copper-Skinner-s.jpg
 
Ken H> said:
I've always been impressed with the copper line in the blade and wanted to try one myself. I did this one with a .070" of 26C3 core, a .030" layer of copper on each side, with a 3/16" of 1075 on each side. After forging and shaping I got this skinner. It's still a bit rough in the ricasso area. It seems the tong hole is popular so I added a bit of paracord with mammoth ivory button.
Copper-Skinner-s.jpg
Click to expand...
Like it ! On which temperature you weld it ?
 
Looks great, to my eye I would go even thinner on the copper, I guess 0.015, or 0.010"...
 
It's forged around 1850F to stay below the melting point of copper. The copper acts as a bonding (soldering?) agent between the two layers of steel.
The billet for that knife was pretty thick with 2 layers of 3/16", a .070", and 2 layers of .030". Knowing it would have to be drawn out I seal welded all the way around, just like San Mai with SS cladding. I did the work in the forge while trying to hold temp around the 1850°F range to prevent melting the copper.

The next I did was with a thinner billet, .040" core of 26C3, .010" copper on each side, and .062" of 410 SS cladding.This I wrapped in SS foil and heated in oven at 1850°F. I figured the oven would help hold the temp more accurately than I could in the forge. Using a 4" flat die in the 16 ton press I just squeezed the foil packet. The first billet done this way I used the drawing dies to to get the billet thinner for kitchen knife, trying to .090 or less. It looked like I did a bit too much pressing and the thin copper didn't like that.
CuMai-2.jpg

So, next billet I just pressed with 16 tons using only full flat die. This blade is the result. After squeezing I expect the core and copper might only be in the .050" thick range, I used the SGA to grind the SS so the final thickness is in the .090" range for the final blade. Still a tad thicker than I like for small kitchen knives, but they work pretty good - and the wife LOVES her some copper :) At .090" with a .050" core/copper thickness that only .020" on each side causing more of the 26C3 core to be exposed than I wished. Especially on this side.
CuMai-3a.jpg

and more copper than I wished on this side:
CuMai-3b.jpg

I think my next attempt will use the drawing die, but gently so it doesn't squeeze quiet so much, but still give a wavy line to the copper.
 
right at the bottom of some of the copper "divots" where it comes right down to the edge there is "almost" no core material like it was squeezed a bit too much. Still 26C3 for the cutting edge, but there isn't much showing - gotta look really close to even see it. I think it's better to have a tad more core metal showing along the edge as in the skinner in first post.
 
I saw the same thing as Ken. The bevel was forged too much before grinding. This left insufficient core at the edge to protrude beyond the cladding. The solution in a new billet is a thicker core. Also, don't forge the blade down as thin at the edge as normal. This will leave enough room to grind back the cladding and expose a sufficient edge width.

It is fixable in an unmounted blade by grinding the edge back a little and re-doing the bevels. This exposes more core. On your finished knife, just consider it a learning experience.
 
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