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M30 x 3.5 tap drill size
Use a 26.5 mm drill to tap M30 x 3.5 (coarse pitch). The rule is major diameter minus pitch: 30 − 3.5 = 26.5 mm. Closest inch drill: 1 in (25.40 mm).
M30 x 3.5 thread specifications
| Thread | M30 x 3.5 ISO metric coarse |
|---|---|
| Major (nominal) diameter | 1.1811 in / 30.00 mm |
| Pitch | 3.5 mm (≈ 7.3 threads per inch) |
| Recommended tap drill | 26.5 mm = 1.0433 in |
M30 clearance hole (ISO 273)
| Fit | Hole diameter |
|---|---|
| Fine (close) | 31 mm |
| Medium (normal) | 33 mm |
| Coarse (loose) | 35 mm |
A clearance hole lets the M30 bolt pass through freely. Drill the tap-drill size only in the part that gets threaded.
Tips for tapping M30 x 3.5
- Use cutting fluid, and with a hand tap back off about half a turn every turn or two to break the chip. Aluminium and soft materials are the exception: they tap cleanly with spiral-point taps.
- For blind holes, drill deeper than the thread you need. Allow at least 3–4 pitches beyond the last full thread for a plug tap (14.0 mm here).
- Thread engagement of 1–1.5 × the diameter (30.0–45.0 mm) is enough for most steel parts. Softer materials need more.