How to punch/drill holes for headstock bearing shims?

[HMF]

To drill holes in thin gauge stock sandwich it between two pieces of plywood and drill through, will be a clean cut every time. I cut the outside edges with an exacto blade.

Or, you can ream or bore a hole in a block of metal to fit a dowel pin, make two additional holes for locating pins, cut it in half, then turn the end of a dowel pin to be flat instead of beveled and you can punch really nice holes in shim stock.

That's the idea behind one of these:

 

[Tony Wells]

I drill and ream a hole in a block the size I want in the shim, and use a ball bearing slightly larger and a hammer. Of course, this will round over the reamed hole after a few uses, but if you don't really pound it, it will make quite a few holes.