engrssc wrote:Thanks for the input, Nick. Otherwise ok?
Yes, otherwise they are OK.
As it happens, I prefer these:
http://www.ebay.co.uk/itm/232257202330 which are about 1/2 the size in terms of diameter (but, perversely, need a somewhat deeper hole). Also the buttons on these don't rotate so I guess one could have them engraved with one or maybe two numerals if desired.
For drilling the holes, I use what I know as a 'flat-bit' but which may be called something else in the USA. If you can't get one of exactly the right size for the button to be a snug push fit in the hole, it's not difficult to buy the next size up and grind or file the sides of the bit, a little at a time, until the hole is just right.
Obviously, it's best to use a piece of scrap timber for this.
Nick