# 41/64" drill size

A 41/64 in drill is 0.6406 in (16.27 mm). It sits between 5/8 in and 21/32 in in the fractional series; the nearest metric drill is 16.3 mm.

## 41/64" drill data

- Series: Fractional drill
- Decimal: 0.6406 in
- Metric: 16.27 mm (16.2719 mm exact)
- Nearest metric drill: 16.3 mm (+0.028 mm)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 16.2 mm | 0.6378 | −0.072 mm |
| 16.3 mm | 0.6417 | +0.028 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| Letter Z | Letter | 0.4130 | 10.49 |
| 5/8" | Fractional | 0.6250 | 15.88 |
| 41/64" | Fractional | 0.6406 | 16.27 |
| 21/32" | Fractional | 0.6562 | 16.67 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| 3/4-10 UNC | 21/32 | 84 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| M14 bolt | 14 mm | 2.27 mm | 1.14 mm | Normal fit (normal 15.5, loose 16.5 mm) |
| 5/8" bolt | 0.6250" | 0.0156" | 0.0078" | – |
| M16 bolt | 16 mm | 0.27 mm | 0.14 mm | Tighter than close fit (17 mm) |


## FAQ

**What size is a 41/64 in drill?**
A 41/64 in drill is 0.6406 in, which is 16.27 mm (16.2719 mm exactly).

**What is the metric equivalent of a 41/64 in drill?**
The nearest metric drill is 16.3 mm, 0.028 mm larger. The other close size is 16.2 mm.

**What thread can I tap with a 41/64 in drill?**
It leaves about 84 % thread in 3/4-10 UNC.

**What does a 41/64 in drill clear?**
It clears a M16 bolt with 0.27 mm total clearance (0.14 mm per side); for metric bolts: tighter than close fit.

Source page: https://machinistcharts.com/drill-size/41-64-inch/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)