M2.5 thread: tap drill, clearance hole and counterbore sizes
The hole sizes and depths for an M2.5 coarse thread, and how to put it on a drawing.
| Property | Value |
|---|---|
| Nominal diameter | 2.5 mm |
| Pitch (coarse) | 0.45 mm |
| Tap drill | Ø2.05 mm |
| Clearance hole, fine | Ø2.7 mm |
| Clearance hole, medium | Ø2.9 mm |
| Clearance hole, coarse | Ø3.1 mm |
| Socket head cap screw head Ø (ISO 4762) | 4.5 mm |
| Counterbore Ø (DIN 974-1) | 5.5 mm |
| Counterbore depth (head flush) | about 3 mm |
Thread depth
| Material | Full thread engagement |
|---|---|
| Steel, stainless steel | 2.5–3.8 mm |
| Aluminium, brass | 3.8–5 mm |
| Plastics | 5–6.3 mm or an insert |
Drill the tap hole at least 1.4–1.8 mm (3–4 pitches) deeper than the full thread, plus the drill point. More on this in how deep a tapped thread should be.
How to call it out on a drawing
Tapped blind hole: M2.5x0.45-6H, thread 3.8 deep, tap drill Ø2.05 5.5 deep.
Clearance hole with counterbore: Ø2.9 through, counterbore Ø5.5 × 3 deep.
M2 | M3 | All thread sizes
Draw your own part
Drop a STEP file into DrawMyPart. It finds every body, asks you to confirm threads, fits and tolerances, and draws a sheet your manufacturer can build from.
Open the tool