Recommendation? Press dies to mimic a Japanese power hammer

[Joshua Fisher]

As the title suggests I’m thinking of making/modifying some press dies to mimic Japanese power hammer dies. My hope is to be able to use these for the blade forging process to both widen and lengthen a bar but hopefully make keeping cores and cladding even on San mai bars. My big question would be is this even a feasible idea or on a thin blade is the press just going to pull out too much heat for this to work, I’d think having both die surfaces domed would help move thin material but I don’t know if I’m just being too optimistic. Here is a photo of what I’d like to end up with and some available dies that I could modify.

 

[Ken H>]

You're addressing a problem I've had with San Mai - thin billets cooling too fast. Are you planning to set the welds with flat dies, then do the "forging" with the rounded dies? Those bottom dies look to be from Coal Iron's 12 ton press - is that correct? That's what I've got and they come with a 3" cylinder giving only 9 tons, but still work darn good. The stroke is fast and that really helps with heat loss - go down, then up as quickly as possible to help prevent heat loss.

I like your idea - keep updating on progress.

 

[Joshua Fisher]

You're addressing a problem I've had with San Mai - thin billets cooling too fast. Are you planning to set the welds with flat dies, then do the "forging" with the rounded dies? Those bottom dies look to be from Coal Iron's 12 ton press - is that correct? That's what I've got and they come with a 3" cylinder giving only 9 tons, but still work darn good. The stroke is fast and that really helps with heat loss - go down, then up as quickly as possible to help prevent heat loss.

I like your idea - keep updating on progress.

These would be more for the blade forging process often using pre laminated stock or after the forge welding process is done. I’ve not had issues on the 12 ton with welding San mai, I usually have atleast a 3/4” thick billet or larger and that holds heat fairly well to set weld with flat dies then I switch to the rounded drawing dies that coal iron makes and they draw stock out in no time. You can also adjust pressure on the press with the hydraulic valve in the pump, they told me you can open it up till the motor starts to stall then close it back just a bit to get the most pressure.

 

[Ken H>]

That's interesting on "increase pressure until motor stalls" - Do you have a pressure gauge to determine what that pressure is? Aren't the hoses / cylinder rated at 3,000 psi? I have bumped my pressure up to 2600 psi and the motor didn't sound all that loaded. with a 4" cylinder I run a good bit lower pressure, but am getting the "full 12 ton" out of the press. A pressure gauge was the first thing I did to the press - gotta know what pressure the system is operating at. When I got my press it was only delivering 8 ton of press with the pressure set around 2250 psi.

I have made San Mai with a thick billet (1/2" or so) and also with a thin billet using .040" core and .060" cladding when trying to get a thin billet for a kitchen knife. Those suck the heat out quickly. I'll set the weld with a 4" long die, reheating between each press.

 

[Wyo Coyote]

If the dies are pulling heat out of the billet too fast you might try and "pre-heat" the dies with hot steel, keeping it between the dies until you're ready to press your billet.