# #3-48 tap drill size

The tap drill for a #3-48 UNC thread is a #47 drill (0.0785 in, 1.99 mm). It leaves about 76 % thread. The closest metric drill is 2.0 mm, which leaves 75 % thread.

## Drill options for #3-48 UNC

| Drill | Inch | Thread % |
|---|---|---|
| #47 | 0.0785 | 76 % |
| 1.9 mm | 0.0748 | 89 % |
| 2.0 mm | 0.0787 | 75 % |
| 2.1 mm | 0.0827 | 60 % |

## #3-48 thread data

- Thread: #3-48 UNC, 48 TPI
- Major diameter: 0.0990 in (2.51 mm)
- Tap drill: #47 = 0.0785 in (1.99 mm)
- Thread engagement: 76 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 48 × 0.0205 / 0.01299 = 76 %.

## FAQ

**What size drill for a #3-48 tap?**
Use a #47 drill (0.0785 in, 1.99 mm). It leaves about 76 % thread.

**Can I use a metric drill for #3-48?**
Yes. A 2.0 mm drill gives about 75 % thread.

Source page: https://machinistcharts.com/tap-drill/3-48/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)