Perhaps less about machining pewter buttons and more about holding them so we could. The pewter buttons have been cast in an open one-sided sand mold. The stars on the front face are the important face to keep. The open casting means the thicknesses are variable.
The big issue was there was no easy way to hold them as pewter is quite soft.
My solution was to machine a relief with a tapered edge into a piece of round mild steel.
The hole is irrelevant and was already there as this was an offcut of metal.
The button would then sit and centre reasonably well in this recess.
You can see the overhanging mass of extra pewter from the casting process.
As the pewter is quite soft I could not just use a sharp centre. So I made a small 6mm diameter brass bobbin that I centre drilled from one end.
I used a small amount of wax to fix this temporarily to the rotating centre. This way I didn’t have to hold quite so many things. Holding the button in the recess, bring up the live centre and brass bobbin to push the pewter against the steel support.
This allowed us to face the the back of the button so that all 8 were 4.5mm thick.
We were left with just a 6mm wide section of pewter in the centre that we just filed off.
So, as described, perhaps less about machining pewter buttons and more about holding them so we could. However, hopefully this gives you another idea for workholding awkward parts.
Sometimes I just have to do something totally different. Not sure if it is because I’m stuck in a groove or just bored. Something though kicks in, I get an idea and I just need to try it. The thing is it absolutely drives me.