8.5 mm Drill Bit Size
An 8.5 mm drill bit is 0.3346 inches. A letter Q drill bit at 0.3320 inches is close, while common fractional choices are 21/64 inch undersized or 11/32 inch oversized.
Quick Answer
Decimal
0.3346 in
Metric
8.50 mm
Closest
Q
8.5 mm Drill Bit Equivalent Chart
| Size | Decimal Inches | Metric | Note |
|---|---|---|---|
| 8.5 mm | 0.3346 in | 8.50 mm | Exact size |
| Q | 0.3320 in | 8.43 mm | Close letter drill size |
| 21/64 inch | 0.3281 in | 8.33 mm | Common fractional undersize |
| 11/32 inch | 0.3438 in | 8.73 mm | Common fractional oversize |
Common Uses
Metric clearance holes and applications where the specified hole is larger than 8 mm.
Exact vs Nearest Size
Choose the exact bit for threads, tight hardware fits, dowels, and precision layouts. Use the nearest common equivalent only for rough pilot holes, clearance holes, or material removal where a slight difference is acceptable.
8.5 mm Drill Bit FAQ
What are the inch and metric dimensions for 8.5 mm?
8.5 mm drill bit measures 0.3346 in and 8.50 mm.
What is the closest common equivalent to 8.5 mm?
Q is the closest common equivalent listed here. It measures 0.3320 in or 8.43 mm.
Can I substitute another bit for 8.5 mm?
Use the exact bit size for tap drilling, precision holes, dowels, and manufacturer-specified hardware. A nearby fractional, metric, numbered, or letter drill bit is usually fine only for clearance holes or rough pilot holes.