Acting on a tip given on the ukulele underground in an old thread I got onto ebay and looked up how much a Diamond coated core drill bit would set me back

Saw a set  described as "3mm ( 1/8" ) to 12mm ( 1/2" ) Diamond coated drill bit hole saw core drills set." for $9.99 in our Australian dollars.

Have not got too serious with it yet but so far it has made short work of making dots out of wood, an old lamb bone, oyster shells, and a beer bottle. The sizing of the bit is to the outer hole, which is about 2.5mm wider than the dot left over. I.e. I got a 8.6mm dot out of a beer bottle using the 11mm bit.

I saw two types, one with a 1/8 dremel size shaft and one which is hollow through to the end for drills, which is what I bought. The hollow one would be easier to get the dots out of as you can stick a nail all the way through.

Perfect for fret and side marking dots in whatever size you choose out of whatever you feel like.