M3 thread: tap drill, clearance hole and counterbore sizes
The hole sizes and depths for an M3 coarse thread, and how to put it on a drawing.
| Property | Value |
|---|---|
| Nominal diameter | 3 mm |
| Pitch (coarse) | 0.5 mm |
| Tap drill | Ø2.5 mm |
| Clearance hole, fine | Ø3.2 mm |
| Clearance hole, medium | Ø3.4 mm |
| Clearance hole, coarse | Ø3.6 mm |
| Socket head cap screw head Ø (ISO 4762) | 5.5 mm |
| Counterbore Ø (DIN 974-1) | 6.5 mm |
| Counterbore depth (head flush) | about 3.5 mm |
Thread depth
| Material | Full thread engagement |
|---|---|
| Steel, stainless steel | 3–4.5 mm |
| Aluminium, brass | 4.5–6 mm |
| Plastics | 6–7.5 mm or an insert |
Drill the tap hole at least 1.5–2 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: M3x0.5-6H, thread 4.5 deep, tap drill Ø2.5 6.5 deep.
Clearance hole with counterbore: Ø3.4 through, counterbore Ø6.5 × 3.5 deep.
M2.5 | M4 | All thread sizes
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