Back in 2008, a Group Buy was done to order all the drill bits commonly used in pen turning.
Here is a list of what was included at that time.
"set includes all the bits needed to make any pen from any major supplier, plus a few that have been mentioned as preferred alternatives.
The big plus with this set is getting all the odd metric size bits as well as all the bits larger than 1/2 inch bits at very low prices.
complete set includes these bits.
7mm, 8mm, 8.2mm, 10mm, 10.5mm, 11mm, 12.5mm, 13.3mm, 14mm,
I, J, L, O, S, T, U, V, X, Z
9/32, 21/64, 11/32, 23/64, 3/8, 25/64, 13/32, 27/64, 7/16, 15/32, 31/64, 1/2,
33/64, 17/32, 35/64, 37/64, 19/32,"