ISO metric · coarse
M36 × 4 tap drill size
For general work, OSG suggests 65–70% of full thread. Harder materials and deep holes want less; the calculator sets it from your material.
Cut tap
32.5 mm
1.2795" · 67% thread
Form tap
34 mm
1.3386" · 74% thread
Or 1-11/32 (1.3438") for 69%
Pick your material for its % of thread, tapping RPM and the rigid-tap code.
Thread dimensions
- Major Ø
- 36.000 mm (1.4173")
- Pitch
- 4 mm
- Pitch Ø (basic)
- 33.402 mm (1.3150")
- Minor Ø (internal, basic)
- 31.670 mm (1.2468")
- Thread depth (internal)
- 2.165 mm (0.0852")
Basic sizes of the 60° form. Tolerance classes (6H) set the limits around them.
Cut tap drills
For a cutting (fluted or spiral) tap. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.
| Drill | Ø in | Ø mm | Thread |
|---|---|---|---|
| 1-1/4 | 1.2500 | 31.75 | 82% |
| 32 mm | 1.2598 | 32.00 | 77% |
| 1-17/64 | 1.2656 | 32.15 | 74% |
| 32.5 mmsuggested | 1.2795 | 32.50 | 67% |
| 1-9/32suggested | 1.2813 | 32.54 | 67% |
| 1-19/64 | 1.2969 | 32.94 | 59% |
| 33 mm | 1.2992 | 33.00 | 58% |
| 1-5/16 | 1.3125 | 33.34 | 51% |
Form tap drills
A form (roll) tap displaces metal instead of cutting it, so it needs a bigger hole. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.
| Drill | Ø in | Ø mm | Thread |
|---|---|---|---|
| 1-21/64 | 1.3281 | 33.73 | 83% |
| 34 mm | 1.3386 | 34.00 | 74% |
| 1-11/32suggested | 1.3438 | 34.13 | 69% |
| 34.5 mm | 1.3583 | 34.50 | 55% |
| 1-23/64 | 1.3594 | 34.53 | 54% |
3-wire measurement
- Best wire size
- 2.309 mm (0.0909")
- Over wires, at basic pitch Ø
- 36.866 mm (1.4514")
For the external thread (the screw). The best wire touches the flanks at the pitch diameter.
Sources
- ISO 261 / ISO 262 — ISO general purpose metric screw threads: general plan and selected sizes
- OSG — Tap drill size and pitch diameter limit chart (formula, suggested % of full thread)
- Cutting Tool Engineering — "Threads will roll": form tap hole size = D − 0.0068 × % / TPI
- ASME B94.11M — Twist drills (fractional, number, letter and metric sizes)
- NIST (NBS) Letter Circular 23 and Pratt & Whitney — three-wire thread measurement, best wire size