ISO metric · coarse
M6 × 1 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
5.1 mm
0.2008" · 69% thread
Form tap
5.5 mm
0.2165" · 74% thread
Or 7/32 (0.2188") for 65%
Pick your material for its % of thread, tapping RPM and the rigid-tap code.
Thread dimensions
- Major Ø
- 6.000 mm (0.2362")
- Pitch
- 1 mm
- Pitch Ø (basic)
- 5.350 mm (0.2106")
- Minor Ø (internal, basic)
- 4.917 mm (0.1936")
- Thread depth (internal)
- 0.541 mm (0.0213")
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 |
|---|---|---|---|
| 4.9 mm | 0.1929 | 4.90 | 85% |
| #10 | 0.1935 | 4.91 | 84% |
| #9 | 0.1960 | 4.98 | 79% |
| 5 mm | 0.1969 | 5.00 | 77% |
| #8 | 0.1990 | 5.05 | 73% |
| 5.1 mmsuggested | 0.2008 | 5.10 | 69% |
| #7suggested | 0.2010 | 5.11 | 69% |
| 13/64suggested | 0.2031 | 5.16 | 65% |
| #6 | 0.2040 | 5.18 | 63% |
| 5.2 mm | 0.2047 | 5.20 | 62% |
| #5 | 0.2055 | 5.22 | 60% |
| 5.3 mm | 0.2087 | 5.30 | 54% |
| #4 | 0.2090 | 5.31 | 53% |
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 |
|---|---|---|---|
| 5.5 mm | 0.2165 | 5.50 | 74% |
| 7/32suggested | 0.2188 | 5.56 | 65% |
| 5.6 mm | 0.2205 | 5.60 | 59% |
| #2 | 0.2210 | 5.61 | 57% |
3-wire measurement
- Best wire size
- 0.577 mm (0.0227")
- Over wires, at basic pitch Ø
- 6.217 mm (0.2447")
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