As Justin stated, the small ones are very good. Clean cut, flat bottom - sizes 1/4, 5/16. 3/8, 7/16 are all very useful.
If you have a patch box, the larger sizes will give you a flat bottom very quickly - then you can use your sharp chisels to square the opening.
Some do not like the little divot that the starting point leaves - it doesn't bother me, as many old ML's show that spur hole. I think it would be a pretty quick job to chisel that final 1/8".
Available from many suppliers. I got mine years ago from Constantine's, down in south Florida. I believe that they are generally available by the 1/16", up to larger than 2" diameter.