M8 thread: tap drill, clearance hole and counterbore sizes
The hole sizes and depths for an M8 coarse thread, and how to put it on a drawing.
| Property | Value |
|---|---|
| Nominal diameter | 8 mm |
| Pitch (coarse) | 1.25 mm |
| Tap drill | Ø6.8 mm |
| Clearance hole, fine | Ø8.4 mm |
| Clearance hole, medium | Ø9 mm |
| Clearance hole, coarse | Ø10 mm |
| Socket head cap screw head Ø (ISO 4762) | 13 mm |
| Counterbore Ø (DIN 974-1) | 15 mm |
| Counterbore depth (head flush) | about 8.5 mm |
Thread depth
| Material | Full thread engagement |
|---|---|
| Steel, stainless steel | 8–12 mm |
| Aluminium, brass | 12–16 mm |
| Plastics | 16–20 mm or an insert |
Drill the tap hole at least 3.8–5 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: M8x1.25-6H, thread 12 deep, tap drill Ø6.8 17 deep.
Clearance hole with counterbore: Ø9 through, counterbore Ø15 × 8.5 deep.
M6 | M10 | All thread sizes
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