# #1-64 tap drill size

The tap drill for a #1-64 UNC thread is a #53 drill (0.0595 in, 1.51 mm). It leaves about 67 % thread. The closest metric drill is 1.5 mm, which leaves 69 % thread.

## Drill options for #1-64 UNC

| Drill | Inch | Thread % |
|---|---|---|
| #53 | 0.0595 | 67 % |
| 1.4 mm | 0.0551 | 88 % |
| 1.5 mm | 0.0591 | 69 % |
| 1.6 mm | 0.0630 | 49 % |

## #1-64 thread data

- Thread: #1-64 UNC, 64 TPI
- Major diameter: 0.0730 in (1.85 mm)
- Tap drill: #53 = 0.0595 in (1.51 mm)
- Thread engagement: 67 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 64 × 0.0135 / 0.01299 = 67 %.

## FAQ

**What size drill for a #1-64 tap?**
Use a #53 drill (0.0595 in, 1.51 mm). It leaves about 67 % thread.

**Can I use a metric drill for #1-64?**
Yes. A 1.5 mm drill gives about 69 % thread.

Source page: https://machinistcharts.com/tap-drill/1-64/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)