#30 Drill Bit Size and Diameter
A #30 drill bit measures 0.1285 in
3.26 mm · number-size drill · common in sheet-metal and 6-48 screw work
The #30 is a numbered drill bit in the American gauge series, measuring 0.1285 inches (3.26 mm). It sits between a #31 bit (0.1200 in) and a #29 bit (0.1360 in) — note there is no #30-adjacent fractional equivalent, which is exactly why number bits exist.
At a glance
| Drill size | #30 |
|---|---|
| Diameter | 0.1285 in |
| Millimetres | 3.26 mm |
| Series | Number drill (gauge) 1–97 |
| Neighbours | #31 (0.1200 in) · #29 (0.1360 in) |
What the #30 is used for
#30 is not a standard tap drill for a common UNC/UNF thread. It is widely used for clearance and pilot work in thin material and for 6-48 / 8-32 screw-hole preparation at a tighter fit.
If you came here looking for an 8-32 tap drill, that is the #29 bit (0.1360 in). The #30 sits just under it and gives a lighter thread fit in soft material.
Related sizes
Other number drill bits
The neighbourhood of the #30 in the gauge series: