# #10-24 tap drill size

The tap drill for a #10-24 UNC thread is a #25 drill (0.1495 in, 3.80 mm). It leaves about 75 % thread. The closest metric drill is 3.8 mm, which leaves 75 % thread.

## Drill options for #10-24 UNC

| Drill | Inch | Thread % |
|---|---|---|
| #25 | 0.1495 | 75 % |
| 3.7 mm | 0.1457 | 82 % |
| 3.8 mm | 0.1496 | 75 % |
| 3.9 mm | 0.1535 | 67 % |

## #10-24 thread data

- Thread: #10-24 UNC, 24 TPI
- Major diameter: 0.1900 in (4.83 mm)
- Tap drill: #25 = 0.1495 in (3.80 mm)
- Thread engagement: 75 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 24 × 0.0405 / 0.01299 = 75 %.

## FAQ

**What size drill for a #10-24 tap?**
Use a #25 drill (0.1495 in, 3.80 mm). It leaves about 75 % thread.

**Can I use a metric drill for #10-24?**
Yes. A 3.8 mm drill gives about 75 % thread.

Source page: https://machinistcharts.com/tap-drill/10-24/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)