31/64" drill size
A 31/64 in drill is 0.4844 in (12.30 mm). It is the standard tap drill for 9/16-12 UNC; the nearest metric drill is 12.3 mm.
31/64" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.4844"
- Millimetres
- 12.30 mm 12.3031
- Nearest metric drill
- 12.3 mm −0.003 mm
- Hole area
- 0.184 in² 118.9 mm²
- Tap drill for
- 9/16-12 UNC
Nearest metric drills
Metric drills step by 0.05 mm below 3 mm and by 0.1 mm from 3 mm. Difference is metric minus inch size.
| Metric drill | Inch | Difference | In inches | Hole |
|---|---|---|---|---|
| 12.3 mm | 0.4843" | −0.003 mm | −0.0001" | Smaller |
| 12.4 mm | 0.4882" | +0.097 mm | +0.0038" | Larger |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a 31/64" drill can tap
Threads from the tap tables on this site that this drill can tap, with the thread percentage it leaves (55–85 % shown).
| Thread | Standard drill | Thread with this drill | Suits |
|---|---|---|---|
| 9/16-12 UNC | 31/64 | 72 % | Standard drill |
| M14 × 2 | 12 mm | 65 % | Good in steel |
Clearance for screws and bolts
Bolts and screws a 31/64" hole clears, with the diametral clearance and the gap each side. Metric sizes are compared with ISO 273.
| Fastener | Diameter | Clearance | Per side | ISO 273, metric only |
|---|---|---|---|---|
| 7/16" bolt | 0.4375" | 0.0469" | 0.0234" | – |
| M12 bolt | 12 mm | 0.30 mm | 0.15 mm | Tighter than close fit (13 mm) |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Fractional drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a 31/64 in drill?
A 31/64 in drill is 0.4844 in, which is 12.30 mm (12.3031 mm exactly).
What is the metric equivalent of a 31/64 in drill?
The nearest metric drill is 12.3 mm, 0.003 mm smaller. The other close size is 12.4 mm.
What tap uses a 31/64 in drill?
A 31/64 in drill is the standard tap drill for 9/16-12 UNC (about 72 % thread).
What does a 31/64 in drill clear?
It clears a M12 bolt with 0.30 mm total clearance (0.15 mm per side); for metric bolts: tighter than close fit.