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Koshira punch and die troubleshoot


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I made a hardwood punch and a steel die for stamping Koshira blanks out the other day. I couldn't resist smacking some copper through to see what I'd get. I'm using bits of copper pipe or connectors flattened out, measures .060" thick or 1.52mm. These are my tools and results so far...


In the first image you can see my tools and copper, I annealed all the copper before hammering through, one anneal one pass.


The second shows how the die matches my punch. It's a little irregular, which I'm unhappy about, but I don't know how much it really effects things? I'm concerned that the radius of the die edge is too tight which causes the problem in the last image.


I reshaped the punch because I didn't like the flat top of the first blank.


For those of you that punch koshira, do you complete the punching in one anneal and one pass? Are my punch and die tolerances okay? Is the edge radius too tight? Any insight would be helpful.


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Edited by TrevorWalsh
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Nice project...the male die looks very loose, I assume you ended up there after attempting a tighter fit. I am not sure what a koshira is.


These shapes may also be created by raising. A steel male plug , a disc of copper ( annealed) and a short piece of steel or very hard wood can be set into a vise. The copper is worked over the male form and will want to wrinkle. The wrinkles can be worked out but have to be supported so they do not create overlaps or shuts. I have made some ferrules that way and find it a good way to go for a 1 off.


I may get a look at koshiras today as I am off to the Japanese Sword Show in San Francisco ( held this weekend ). My primary interest is to see the steel and see if I can buy a couple of water stones.




Edited by Jan Ysselstein
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