# 5/8-11 tap drill size

The tap drill for a 5/8-11 UNC thread is a 17/32 drill (0.5313 in, 13.50 mm). It leaves about 79 % thread. The closest metric drill is 13.5 mm, which leaves 79 % thread.

## Drill options for 5/8-11 UNC

| Drill | Inch | Thread % |
|---|---|---|
| 17/32 | 0.5313 | 79 % |
| 13.4 mm | 0.5276 | 83 % |
| 13.5 mm | 0.5315 | 79 % |
| 13.6 mm | 0.5354 | 76 % |

## 5/8-11 thread data

- Thread: 5/8-11 UNC, 11 TPI
- Major diameter: 0.6250 in (15.88 mm)
- Tap drill: 17/32 = 0.5313 in (13.50 mm)
- Thread engagement: 79 %

## Method

Thread % = TPI × (D − drill) / 0.01299 = 11 × 0.0937 / 0.01299 = 79 %.

## FAQ

**What size drill for a 5/8-11 tap?**
Use a 17/32 drill (0.5313 in, 13.50 mm). It leaves about 79 % thread.

**Can I use a metric drill for 5/8-11?**
Yes. A 13.5 mm drill gives about 79 % thread.

**How tight should a 5/8 grade 5 bolt be?**
About 150 ft-lb dry for 5/8-11 UNC.

Source page: https://machinistcharts.com/tap-drill/5-8-11/
Updated: 2026-10-05
Publisher: MachinistCharts (https://machinistcharts.com)