ISO metric · coarse
M48 × 5 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
43.5 mm
1.7126" · 69% thread
Form tap
45.5 mm
1.7913" · 74% thread
Or 1-51/64 (1.7969") for 69%
Pick your material for its % of thread, tapping RPM and the rigid-tap code.
Thread dimensions
- Major Ø
- 48.000 mm (1.8898")
- Pitch
- 5 mm
- Pitch Ø (basic)
- 44.752 mm (1.7619")
- Minor Ø (internal, basic)
- 42.587 mm (1.6767")
- Thread depth (internal)
- 2.706 mm (0.1065")
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 |
|---|---|---|---|
| 42.5 mm | 1.6732 | 42.50 | 85% |
| 1-11/16 | 1.6875 | 42.86 | 79% |
| 43 mm | 1.6929 | 43.00 | 77% |
| 1-45/64 | 1.7031 | 43.26 | 73% |
| 43.5 mmsuggested | 1.7126 | 43.50 | 69% |
| 1-23/32suggested | 1.7188 | 43.66 | 67% |
| 44 mm | 1.7323 | 44.00 | 62% |
| 1-47/64 | 1.7344 | 44.05 | 61% |
| 1-3/4 | 1.7500 | 44.45 | 55% |
| 44.5 mm | 1.7520 | 44.50 | 54% |
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 |
|---|---|---|---|
| 1-25/32 | 1.7813 | 45.24 | 81% |
| 45.5 mm | 1.7913 | 45.50 | 74% |
| 1-51/64suggested | 1.7969 | 45.64 | 69% |
| 46 mm | 1.8110 | 46.00 | 59% |
| 1-13/16 | 1.8125 | 46.04 | 58% |
3-wire measurement
- Best wire size
- 2.887 mm (0.1137")
- Over wires, at basic pitch Ø
- 49.083 mm (1.9324")
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