# #55 drill size

A #55 drill is 0.0520 in (1.32 mm). It sits between #56 and #54 in the number series; the nearest metric drill is 1.3 mm.

## #55 drill data

- Series: Number drill
- Decimal: 0.0520 in
- Metric: 1.32 mm (1.3208 mm exact)
- Nearest metric drill: 1.3 mm (−0.021 mm)
- Nearest fractional: 3/64" (0.0469 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 1.3 mm | 0.0512 | −0.021 mm |
| 1.35 mm | 0.0531 | +0.029 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #56 | Number | 0.0465 | 1.18 |
| 3/64" | Fractional | 0.0469 | 1.19 |
| #55 | Number | 0.0520 | 1.32 |
| #54 | Number | 0.0550 | 1.40 |
| 1/16" | Fractional | 0.0625 | 1.59 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M1.6 × 0.35 | 1.25 mm | 61 |


## FAQ

**What size is a #55 drill?**
A #55 drill is 0.0520 in, which is 1.32 mm (1.3208 mm exactly).

**What is the metric equivalent of a #55 drill?**
The nearest metric drill is 1.3 mm, 0.021 mm smaller. The other close size is 1.35 mm.

**What thread can I tap with a #55 drill?**
It leaves about 61 % thread in M1.6 × 0.35.

**Which fractional drill is closest to #55?**
3/64 in (0.0469 in) is the closest, 0.0051 in smaller.

Source page: https://machinistcharts.com/drill-size/number-55/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)