In a recent experience i modified some leather belts by adding some extra loop holes. I found my bicycle dremel to be the perfect device for drilling holes in leather (and probably plastic B-18 saddles as well.) At 20,000 RPM, the holes are perfectly formed with no shredding around the edges. Careful hole positioning is important for a 'factory look'. There are dremel bits that look like helical gears and these where what i used to get a uniform hole.
http://www.engineersedge.com/
- Don Gillies
San Diego, CA, USA