# #19 drill size

A #19 drill is 0.1660 in (4.22 mm). It sits between #20 and #18 in the number series; the nearest metric drill is 4.2 mm.

## #19 drill data

- Series: Number drill
- Decimal: 0.1660 in
- Metric: 4.22 mm (4.2164 mm exact)
- Nearest metric drill: 4.2 mm (−0.016 mm)
- Nearest fractional: 11/64" (0.1719 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 4.2 mm | 0.1654 | −0.016 mm |
| 4.3 mm | 0.1693 | +0.084 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 5/32" | Fractional | 0.1562 | 3.97 |
| #20 | Number | 0.1610 | 4.09 |
| #19 | Number | 0.1660 | 4.22 |
| #18 | Number | 0.1695 | 4.31 |
| 11/64" | Fractional | 0.1719 | 4.37 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M5 × 0.8 | 4.2 mm | 75 |
| #10-32 UNF | #21 | 59 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #4 screw | 0.1120" | 0.0540" | 0.0270" | – |
| #5 screw | 0.1250" | 0.0410" | 0.0205" | – |
| #6 screw | 0.1380" | 0.0280" | 0.0140" | – |
| M4 bolt | 4 mm | 0.22 mm | 0.11 mm | Tighter than close fit (4.3 mm) |
| #8 screw | 0.1640" | 0.0020" | 0.0010" | – |


## FAQ

**What size is a #19 drill?**
A #19 drill is 0.1660 in, which is 4.22 mm (4.2164 mm exactly).

**What is the metric equivalent of a #19 drill?**
The nearest metric drill is 4.2 mm, 0.016 mm smaller. The other close size is 4.3 mm.

**What thread can I tap with a #19 drill?**
It leaves about 75 % thread in M5 × 0.8 and 59 % in #10-32 UNF.

**Which fractional drill is closest to #19?**
11/64 in (0.1719 in) is the closest, 0.0059 in larger.

**What does a #19 drill clear?**
It clears a #8 screw with 0.0020" total clearance (0.0010" per side).

Source page: https://machinistcharts.com/drill-size/number-19/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)