I suggest getting a bag of 80 grit and a bag of 120 grit.  The 80 grit is good for enlarging holes that have become too small -- usually for your junior bowlers.  The 120 grit is perfect for normal beveling and sanding after drilling.  I keep a spare bevel sander supplied with an ~1" square piece of 400 grit sandpaper for final smoothing after the rough work is done.  When I've used the 80 grit, I follow up by smoothing with the 120 grit, then finish with the 400 grit.  --  JohnP

Added on edit:  My response assumed you operate a shop and will be working on customer's equipment.  If you'll only be working on yours, get the 120 grit.

Edited on 1/13/2006 11:57 AM