# 45/64" drill size

A 45/64 in drill is 0.7031 in (17.86 mm). It sits between 11/16 in and 23/32 in in the fractional series; the nearest metric drill is 17.9 mm.

## 45/64" drill data

- Series: Fractional drill
- Decimal: 0.7031 in
- Metric: 17.86 mm (17.8594 mm exact)
- Nearest metric drill: 17.9 mm (+0.041 mm)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 17.8 mm | 0.7008 | −0.059 mm |
| 17.9 mm | 0.7047 | +0.041 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| Letter Z | Letter | 0.4130 | 10.49 |
| 11/16" | Fractional | 0.6875 | 17.46 |
| 45/64" | Fractional | 0.7031 | 17.86 |
| 23/32" | Fractional | 0.7188 | 18.26 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M20 × 2.5 | 17.5 mm | 66 |
| 3/4-16 UNF | 11/16 | 58 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| M16 bolt | 16 mm | 1.86 mm | 0.93 mm | Normal fit (normal 17.5, loose 18.5 mm) |


## FAQ

**What size is a 45/64 in drill?**
A 45/64 in drill is 0.7031 in, which is 17.86 mm (17.8594 mm exactly).

**What is the metric equivalent of a 45/64 in drill?**
The nearest metric drill is 17.9 mm, 0.041 mm larger. The other close size is 17.8 mm.

**What thread can I tap with a 45/64 in drill?**
It leaves about 66 % thread in M20 × 2.5 and 58 % in 3/4-16 UNF.

**What does a 45/64 in drill clear?**
It clears a M16 bolt with 1.86 mm total clearance (0.93 mm per side); for metric bolts: normal fit.

Source page: https://machinistcharts.com/drill-size/45-64-inch/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)