# 3/4-16 tap drill size

The tap drill for a 3/4-16 UNF thread is a 11/16 drill (0.6875 in, 17.46 mm). It leaves about 77 % thread. The closest metric drill is 17.5 mm, which leaves 75 % thread.

## Drill options for 3/4-16 UNF

| Drill | Inch | Thread % |
|---|---|---|
| 11/16 | 0.6875 | 77 % |
| 17.4 mm | 0.6850 | 80 % |
| 17.5 mm | 0.6890 | 75 % |
| 17.6 mm | 0.6929 | 70 % |

## 3/4-16 thread data

- Thread: 3/4-16 UNF, 16 TPI
- Major diameter: 0.7500 in (19.05 mm)
- Tap drill: 11/16 = 0.6875 in (17.46 mm)
- Thread engagement: 77 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 16 × 0.0625 / 0.01299 = 77 %.

## FAQ

**What size drill for a 3/4-16 tap?**
Use a 11/16 drill (0.6875 in, 17.46 mm). It leaves about 77 % thread.

**Can I use a metric drill for 3/4-16?**
Yes. A 17.5 mm drill gives about 75 % thread.

**How tight should a 3/4 grade 5 bolt be?**
About 297 ft-lb dry for 3/4-16 UNF.

Source page: https://machinistcharts.com/tap-drill/3-4-16/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)