M3 tap drill size (ISO coarse)
M3 tap drill size is 2.5 mm for standard 0.5 mm coarse pitch under common ISO workshop tables.
Fine pitch 0.35 mm changes the subtractive tap drill rule, so always confirm against your tap manufacturer sheet.
Use the tap drill calculator on BoltLab, then cross-check the bolt size chart hub for hex and pitch context.
Workshop practice often uses major diameter minus pitch; your tap packaging may specify a slightly different pilot for thread percentage.
M3 tap drill reference
| Item | Value |
|---|---|
| Coarse pitch | 0.5 mm |
| Typical tap drill (coarse) | 2.5 mm |
| Fine pitch (common) | 0.35 mm |
Shop workflow
Drill the pilot, chamfer the hole, then tap with cutting fluid and aligned squareness. Re-measure pitch with a gauge if the part is safety-critical.
M3 links and tools
Open the bolt size chart (M3) for hex, pitch, and tap drill in one hub table.
Use tap drill size when pitch differs from coarse or you need a quick recalculation.
Run the thread identifier after you measure major diameter and pitch on a sample thread.
Compare stocked inch hardware with screw size conversion when you cross-shop bins.
Convert pitch units with the thread pitch chart tool when drawings mix mm and TPI.
Review metric vs unc thread naming before you mix UNC taps with metric holes.
Neighbor metric hub: bolt size chart (M4) for the next larger shank.