---
type: "drill"
designation: "2.15 mm"
series: "metric"
series_name: "Metric Drill Sizes"
diameter_in: 0.084646
diameter_mm: 2.15
standard: "ANSI/ASME B94.11M; BS 328"
verified: "August 1, 2026"
url: https://shopmath.org/drills/metric/2-15mm
---

# 2.15 mm Drill Bit Size — 0.0846 in / 2.150 mm

A 2.15 mm drill bit is 0.0846 in (2.150 mm) in diameter. It belongs to the metric series of standard twist drills. It is the recommended tap drill for M2.5×0.35.

- **Designation**: 2.15 mm
- **Series**: Metric
- **Diameter**: 0.0846 in (2.150 mm)

## 2.15 mm Drill Diameter

| Property | Value |
| --- | --- |
| Designation | 2.15 mm |
| Series | Metric |
| Diameter (in) | 0.0846 |
| Diameter (mm) | 2.150 |

## 2.15 mm Drill Equivalents in the Other Size Series

The nearest standard drill to 2.15 mm in each of the other three series. Nothing here is an exact match unless the difference column reads 0.0000 in.

| Series | Nearest drill | Diameter (in) | Diameter (mm) | Difference |
| --- | --- | --- | --- | --- |
| Number | [#44](https://shopmath.org/drills/number/44.md) | 0.0860 | 2.184 | +0.0014 in |
| Letter | [A](https://shopmath.org/drills/letter/a.md) | 0.2340 | 5.944 | +0.1494 in |
| Fractional | [5/64](https://shopmath.org/drills/fractional/5-64.md) | 0.0781 | 1.984 | -0.0065 in |

## Threads Tapped With a 2.15 mm Drill

| Thread | Pitch | Thread engagement (%) |
| --- | --- | --- |
| [M2.5×0.35](https://shopmath.org/threads/metric-fine/m2.5x0.35.md) | 0.350 mm | 77.0 |

_Engagement is what the real drill leaves with a cut tap, not the requested target._

## Sources and Method for the 2.15 mm Drill Size

### Drill index

- **Source**: Number/letter: bd_warehouse drill_sizes.csv (Apache-2.0) cross-checked against Wikipedia Drill bit sizes (CC BY-SA 4.0). Fractional: computed 1/64 in steps per ANSI B94.11M. Metric: computed BS 328 increment pattern.
- **Method**: computed
- **Verified against**: Wikipedia Drill bit sizes (CC BY-SA 4.0); 31/31 checks passed

### Assumptions

- Drill diameters are nominal. A worn or run-out drill cuts oversize; measure the hole, not the shank, when the fit matters.
- Dataset scope: Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.

**Data last verified**: August 1, 2026

## Common Questions About the 2.15 mm Drill Bit

### What size is a 2.15 mm drill bit size?

A 2.15 mm drill bit is 0.0846 in (2.150 mm) in diameter.

### What fraction is a 2.15 mm drill bit?

2.15 mm is 0.0846 in (2.150 mm), which is not itself a fractional size. The closest fractional drill is 5/64 at 0.0781 in (1.984 mm).

### What thread does a 2.15 mm drill bit tap?

A 2.15 mm drill is the recommended tap drill for M2.5×0.35. That leaves the thread engagement shown in the table above with a cut tap.

## Related pages

- Next size down (any series): [2.1 mm](https://shopmath.org/drills/metric/2-1mm.md) — 0.0827 in (2.100 mm)
- Next size up (any series): [#44](https://shopmath.org/drills/number/44.md) — 0.0860 in (2.184 mm)
- Previous in the metric series: [2.1 mm](https://shopmath.org/drills/metric/2-1mm.md)
- Next in the metric series: [2.2 mm](https://shopmath.org/drills/metric/2-2mm.md)
- All metric sizes: [Metric drill sizes](https://shopmath.org/drills/metric.md)
- All drill sizes: [Drill bit size reference](https://shopmath.org/drills.md)
- Complete index by diameter: [Drill size chart](https://shopmath.org/charts/drill-sizes.md)
- Tap drills by thread: [Tap drill chart](https://shopmath.org/charts/tap-drill.md)

---

*Source: [ShopMath](https://shopmath.org/drills/metric/2-15mm) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*