#29 Drill Bit Size and Diameter
A #29 drill bit measures 0.1360 in
3.45 mm · number-size drill · used as the 8-32 tap drill
The #29 is a numbered drill bit in the American gauge series, measuring 0.1360 inches (3.45 mm). It sits between a #30 bit (0.1285 in) and a 9/64 in bit (0.1406 in). It is best known as the standard tap drill for an 8-32 UNC machine screw thread.
At a glance
| Drill size | #29 |
|---|---|
| Diameter | 0.1360 in |
| Millimetres | 3.45 mm |
| Series | Number drill (gauge) 1–97 |
| Closest fractional | 9/64 in (0.1406 in, slightly larger) |
What the #29 is used for
8-32 tap drill: drillØ = major − (pitch × 0.75) = 0.1640 − (0.0313 × 0.75) = 0.1405 in → nearest standard bit = #29 (0.1360 in)
A #29 hole before an 8-32 tap gives the standard ~75% thread engagement. For a clearance hole (bolt passes through unthreaded) a #15 bit is the close fit — bigger than the tap drill on purpose.
Related sizes
Other number drill bits
The neighbourhood of the #29 in the gauge series: