# 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" drill data

- Series: Fractional drill
- Decimal: 0.4844 in
- Metric: 12.30 mm (12.3031 mm exact)
- Nearest metric drill: 12.3 mm (−0.003 mm)
- Standard tap drill for: 9/16-12 UNC

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 12.3 mm | 0.4843 | −0.003 mm |
| 12.4 mm | 0.4882 | +0.097 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| Letter Z | Letter | 0.4130 | 10.49 |
| 15/32" | Fractional | 0.4688 | 11.91 |
| 31/64" | Fractional | 0.4844 | 12.30 |
| 1/2" | Fractional | 0.5000 | 12.70 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| 9/16-12 UNC | 31/64 | 72 |
| M14 × 2 | 12 mm | 65 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| 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) |


## FAQ

**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.

Source page: https://machinistcharts.com/drill-size/31-64-inch/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)