sheet.........26 ga. I haven't hammered it in yet, I'm reviewing options on burr raising to make sure it stays put. Then I'll play around with shading etc.
Make sure your burrs are strong, the copper as soft as you can get it and back the handle scale very solidly. It will take a fairly stiff blow to set the sheet. Also you want undercuts around the outline to help hold the edges of the inlay from being easily lifted. Backing the knife handle so there can be no bounce is probably the most important part.
Paps, you really should take the scale off the knife and back it to set the copper. With the knife together you have gaps that will not give the support needed. On hard stainless it helps with vibration too less broken tips.
For small sheet like that I use a flat polished stainless tool blank with handle that covers the whole inlay (laying flat across the inlay) and give it a good whack first time to set the inlay. After that a punch can be used to go over the area to insure a good set everywhere. I find the flat makes it much easier to set the inlay without it getting out from under a punch. As flint says the scale needs to be solidly backed. If not removable then make a steel thin insert that is a light press fit into the slot to support, and support the other side of the knife. You want no vibration/movement of the handle.
I am going to put MORE HEAT on it and see if they break loose then. I definitley would prefer to to seperate the scale from the frame. guess the worst could happen and I would have to put a brass/bronze back bone in,,,,,,,,,,,,
To clarify my comments...you could use even a good hard wood (such as maple) for the insert which would be easier to make. And I use my chasing hammer for setting the inlay so my "whack" is not as hard as it sounds.
A little more heat released the screws finally, the rest of this day was spent sharpening and stoning OOPSIES around the escavation area. Done.............so not to bad. I have a little more leveling to do and sharpening the side wall, then I'm climb on and have a go at it. I look forward to the generous comments and help on this web site. Thanks goes to you Sam...........................paps