# #27 drill size

A #27 drill is 0.1440 in (3.66 mm). It sits between #28 and #26 in the number series; the nearest metric drill is 3.7 mm.

## #27 drill data

- Series: Number drill
- Decimal: 0.1440 in
- Metric: 3.66 mm (3.6576 mm exact)
- Nearest metric drill: 3.7 mm (+0.042 mm)
- Nearest fractional: 9/64" (0.1406 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 3.6 mm | 0.1417 | −0.058 mm |
| 3.7 mm | 0.1457 | +0.042 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #28 | Number | 0.1405 | 3.57 |
| 9/64" | Fractional | 0.1406 | 3.57 |
| #27 | Number | 0.1440 | 3.66 |
| #26 | Number | 0.1470 | 3.73 |
| 5/32" | Fractional | 0.1562 | 3.97 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| #10-24 UNC | #25 | 85 |
| #8-36 UNF | #29 | 55 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #2 screw | 0.0860" | 0.0580" | 0.0290" | – |
| #3 screw | 0.0990" | 0.0450" | 0.0225" | – |
| #4 screw | 0.1120" | 0.0320" | 0.0160" | – |
| #5 screw | 0.1250" | 0.0190" | 0.0095" | – |
| M3.5 bolt | 3.5 mm | 0.16 mm | 0.08 mm | Tighter than close fit (3.7 mm) |
| #6 screw | 0.1380" | 0.0060" | 0.0030" | – |


## FAQ

**What size is a #27 drill?**
A #27 drill is 0.1440 in, which is 3.66 mm (3.6576 mm exactly).

**What is the metric equivalent of a #27 drill?**
The nearest metric drill is 3.7 mm, 0.042 mm larger. The other close size is 3.6 mm.

**What thread can I tap with a #27 drill?**
It leaves about 85 % thread in #10-24 UNC and 55 % in #8-36 UNF.

**Which fractional drill is closest to #27?**
9/64 in (0.1406 in) is the closest, 0.0034 in smaller.

**What does a #27 drill clear?**
It clears a #6 screw with 0.0060" total clearance (0.0030" per side).

Source page: https://machinistcharts.com/drill-size/number-27/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)