# 21/32" drill size

A 21/32 in drill is 0.6562 in (16.67 mm). It is the standard tap drill for 3/4-10 UNC; the nearest metric drill is 16.7 mm.

## 21/32" drill data

- Series: Fractional drill
- Decimal: 0.6562 in
- Metric: 16.67 mm (16.6687 mm exact)
- Nearest metric drill: 16.7 mm (+0.031 mm)
- Standard tap drill for: 3/4-10 UNC

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 16.6 mm | 0.6535 | −0.069 mm |
| 16.7 mm | 0.6575 | +0.031 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| Letter Z | Letter | 0.4130 | 10.49 |
| 41/64" | Fractional | 0.6406 | 16.27 |
| 21/32" | Fractional | 0.6562 | 16.67 |
| 43/64" | Fractional | 0.6719 | 17.07 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| 3/4-10 UNC | 21/32 | 72 |
| M18 × 1.5 | 16.5 mm | 68 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| 5/8" bolt | 0.6250" | 0.0312" | 0.0156" | – |
| M16 bolt | 16 mm | 0.67 mm | 0.33 mm | Tighter than close fit (17 mm) |


## FAQ

**What size is a 21/32 in drill?**
A 21/32 in drill is 0.6562 in, which is 16.67 mm (16.6687 mm exactly).

**What is the metric equivalent of a 21/32 in drill?**
The nearest metric drill is 16.7 mm, 0.031 mm larger. The other close size is 16.6 mm.

**What tap uses a 21/32 in drill?**
A 21/32 in drill is the standard tap drill for 3/4-10 UNC (about 72 % thread).

**What does a 21/32 in drill clear?**
It clears a M16 bolt with 0.67 mm total clearance (0.33 mm per side); for metric bolts: tighter than close fit.

Source page: https://machinistcharts.com/drill-size/21-32-inch/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)