# 9/16-12 tap drill size

The tap drill for a 9/16-12 UNC thread is a 31/64 drill (0.4844 in, 12.30 mm). It leaves about 72 % thread. The closest metric drill is 12.3 mm, which leaves 72 % thread.

## Drill options for 9/16-12 UNC

| Drill | Inch | Thread % |
|---|---|---|
| 31/64 | 0.4844 | 72 % |
| 12.2 mm | 0.4803 | 76 % |
| 12.3 mm | 0.4843 | 72 % |
| 12.4 mm | 0.4882 | 69 % |

## 9/16-12 thread data

- Thread: 9/16-12 UNC, 12 TPI
- Major diameter: 0.5625 in (14.29 mm)
- Tap drill: 31/64 = 0.4844 in (12.30 mm)
- Thread engagement: 72 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 12 × 0.0781 / 0.01299 = 72 %.

## FAQ

**What size drill for a 9/16-12 tap?**
Use a 31/64 drill (0.4844 in, 12.30 mm). It leaves about 72 % thread.

**Can I use a metric drill for 9/16-12?**
Yes. A 12.3 mm drill gives about 72 % thread.

**How tight should a 9/16 grade 5 bolt be?**
About 109 ft-lb dry for 9/16-12 UNC.

Source page: https://machinistcharts.com/tap-drill/9-16-12/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)