ISO metric · coarse
M5 × 0.8 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
4.3 mm
0.1693" · 67% thread
Form tap
4.6 mm
0.1811" · 74% thread
Or #14 (0.1820") for 69%
Pick your material for its % of thread, tapping RPM and the rigid-tap code.
Thread dimensions
- Major Ø
- 5.000 mm (0.1969")
- Pitch
- 0.8 mm
- Pitch Ø (basic)
- 4.480 mm (0.1764")
- Minor Ø (internal, basic)
- 4.134 mm (0.1628")
- Thread depth (internal)
- 0.433 mm (0.0170")
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 |
|---|---|---|---|
| 4.2 mm | 0.1654 | 4.20 | 77% |
| #19 | 0.1660 | 4.22 | 75% |
| 4.3 mmsuggested | 0.1693 | 4.30 | 67% |
| #18suggested | 0.1695 | 4.31 | 67% |
| 11/64 | 0.1719 | 4.37 | 61% |
| #17 | 0.1730 | 4.39 | 58% |
| 4.4 mm | 0.1732 | 4.40 | 58% |
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 |
|---|---|---|---|
| #15 | 0.1800 | 4.57 | 79% |
| 4.6 mm | 0.1811 | 4.60 | 74% |
| #14suggested | 0.1820 | 4.62 | 69% |
| #13 | 0.1850 | 4.70 | 55% |
| 4.7 mm | 0.1850 | 4.70 | 55% |
3-wire measurement
- Best wire size
- 0.462 mm (0.0182")
- Over wires, at basic pitch Ø
- 5.173 mm (0.2037")
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