Drill Bit Size Calculator — Precision Holes

Use a drill bit that matches your pin diameter. For 0.8mm brass rod, use a 0.8mm bit. For 1.0mm piano wire, use a 1.0mm bit. A slightly larger bit (0.1mm oversize) makes insertion easier but gives a weaker joint — fill any gap with CA glue.

A basic set covers 0.3mm to 2.0mm in 0.1mm increments. The most commonly used sizes are 0.5mm (fine detail), 0.8mm (pinning), and 1.0mm (larger pins). Buy quality HSS bits — cheap ones snap easily at small diameters.

A pin vise (hand drill) is essential for model work. It gives you precise control and prevents breaking small bits. Power drills spin too fast and can crack plastic. Use a pin vise with double-ended collets to hold any bit from 0.1mm to 3.0mm.

Keep the bit perpendicular to the surface. Let the bit do the work — do not press hard. Clear swarf frequently by withdrawing the bit. Start with a smaller pilot hole for larger sizes. Replace blunt bits — they need more pressure and are more likely to snap.