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M16 x 2 tap drill size
Use a 14 mm drill to tap M16 x 2 (coarse pitch). The rule is major diameter minus pitch: 16 − 2 = 14 mm. Closest inch drill: 35/64 (13.89 mm).
M16 x 2 thread specifications
| Thread | M16 x 2 ISO metric coarse |
|---|---|
| Major (nominal) diameter | .6299 in / 16.00 mm |
| Pitch | 2 mm (≈ 12.7 threads per inch) |
| Recommended tap drill | 14 mm = .5512 in |
M16 clearance hole (ISO 273)
| Fit | Hole diameter |
|---|---|
| Fine (close) | 17 mm |
| Medium (normal) | 17.5 mm |
| Coarse (loose) | 18.5 mm |
A clearance hole lets the M16 bolt pass through freely. Drill the tap-drill size only in the part that gets threaded.
Tips for tapping M16 x 2
- 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 (8.0 mm here).
- Thread engagement of 1–1.5 × the diameter (16.0–24.0 mm) is enough for most steel parts. Softer materials need more.