# #38 drill size

A #38 drill is 0.1015 in (2.58 mm). It is the standard tap drill for #5-40 UNC; the nearest metric drill is 2.6 mm.

## #38 drill data

- Series: Number drill
- Decimal: 0.1015 in
- Metric: 2.58 mm (2.5781 mm exact)
- Nearest metric drill: 2.6 mm (+0.022 mm)
- Nearest fractional: 3/32" (0.0938 in)
- Standard tap drill for: #5-40 UNC

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 2.55 mm | 0.1004 | −0.028 mm |
| 2.6 mm | 0.1024 | +0.022 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 3/32" | Fractional | 0.0938 | 2.38 |
| #39 | Number | 0.0995 | 2.53 |
| #38 | Number | 0.1015 | 2.58 |
| #37 | Number | 0.1040 | 2.64 |
| 7/64" | Fractional | 0.1094 | 2.78 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| #5-40 UNC | #38 | 72 |
| #5-44 UNF | #37 | 80 |
| M3 × 0.5 | 2.5 mm | 65 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #1 screw | 0.0730" | 0.0285" | 0.0143" | – |
| M2 bolt | 2 mm | 0.58 mm | 0.29 mm | Normal fit (normal 2.4, loose 2.6 mm) |
| #2 screw | 0.0860" | 0.0155" | 0.0078" | – |
| M2.5 bolt | 2.5 mm | 0.08 mm | 0.04 mm | Tighter than close fit (2.7 mm) |
| #3 screw | 0.0990" | 0.0025" | 0.0013" | – |


## FAQ

**What size is a #38 drill?**
A #38 drill is 0.1015 in, which is 2.58 mm (2.5781 mm exactly).

**What is the metric equivalent of a #38 drill?**
The nearest metric drill is 2.6 mm, 0.022 mm larger. The other close size is 2.55 mm.

**What tap uses a #38 drill?**
A #38 drill is the standard tap drill for #5-40 UNC (about 72 % thread).

**Which fractional drill is closest to #38?**
3/32 in (0.0938 in) is the closest, 0.0078 in smaller.

**What does a #38 drill clear?**
It clears a #3 screw with 0.0025" total clearance (0.0013" per side).

Source page: https://machinistcharts.com/drill-size/number-38/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)