# #1-72 tap drill size

The tap drill for a #1-72 UNF thread is a #53 drill (0.0595 in, 1.51 mm). It leaves about 75 % thread. The closest metric drill is 1.5 mm, which leaves 77 % thread.

## Drill options for #1-72 UNF

| Drill | Inch | Thread % |
|---|---|---|
| #53 | 0.0595 | 75 % |
| 1.4 mm | 0.0551 | 99 % |
| 1.5 mm | 0.0591 | 77 % |
| 1.6 mm | 0.0630 | 55 % |

## #1-72 thread data

- Thread: #1-72 UNF, 72 TPI
- Major diameter: 0.0730 in (1.85 mm)
- Tap drill: #53 = 0.0595 in (1.51 mm)
- Thread engagement: 75 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 72 × 0.0135 / 0.01299 = 75 %.

## FAQ

**What size drill for a #1-72 tap?**
Use a #53 drill (0.0595 in, 1.51 mm). It leaves about 75 % thread.

**Can I use a metric drill for #1-72?**
Yes. A 1.5 mm drill gives about 77 % thread.

Source page: https://machinistcharts.com/tap-drill/1-72/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)