MAN4MACHINEMJ20 x 1.5
Aerospace / High-Fatigue
Dimensionally an M thread at the pitch diameter -- same 60 degree flank, same pitch-diameter formula -- but the root is cut to a controlled minimum radius (rather than M's unspecified, often flat-truncated root) so the thread can survive repeated fatigue cycling. Used across aerospace and other high-fatigue fastening. Pitch-diameter and tolerance math is identical to M; the radius is a manufacturing and inspection requirement this database records but does not turn into a different basic diameter.
- Standard
- ISO 5855 / MIL-S-8879
- Flank angle
- 60° included
- Series
- Fine pitch
- Pitch
- 1.50 mm
- Coarse default
Thread profile
A 60 degree included flank angle, with a controlled root radius rather than a flat truncation -- the fatigue-resistant detail this diagram's rounded root stands in for.
Basic major 20.000 mm, pitch diameter 19.026 mm, minor diameter 18.376 mm -- theoretical dimensions at zero allowance, before any tolerance class is applied.
MJ fine sizes
| Designation | Pitch | Major Ø | Pitch Ø | Minor Ø |
|---|---|---|---|---|
| MJ8 x 1 | 1.00 mm | 8.00 mm | 7.350 mm | 6.917 mm |
| MJ10 x 1.25 | 1.25 mm | 10.00 mm | 9.188 mm | 8.647 mm |
| MJ12 x 1.25 | 1.25 mm | 12.00 mm | 11.188 mm | 10.647 mm |
| MJ14 x 1.5 | 1.50 mm | 14.00 mm | 13.026 mm | 12.376 mm |
| MJ16 x 1.5 | 1.50 mm | 16.00 mm | 15.026 mm | 14.376 mm |
| MJ18 x 1.5 | 1.50 mm | 18.00 mm | 17.026 mm | 16.376 mm |
| MJ20 x 1.5 | 1.50 mm | 20.00 mm | 19.026 mm | 18.376 mm |
| MJ22 x 1.5 | 1.50 mm | 22.00 mm | 21.026 mm | 20.376 mm |
| MJ24 x 2 | 2.00 mm | 24.00 mm | 22.701 mm | 21.835 mm |
| MJ27 x 2 | 2.00 mm | 27.00 mm | 25.701 mm | 24.835 mm |
| MJ30 x 2 | 2.00 mm | 30.00 mm | 28.701 mm | 27.835 mm |
| MJ33 x 2 | 2.00 mm | 33.00 mm | 31.701 mm | 30.835 mm |
| MJ36 x 3 | 3.00 mm | 36.00 mm | 34.051 mm | 32.752 mm |
Designation calculator
Try “M12x1.5-6g”, “M8” (coarse pitch assumed), “MJ6-4h6h”, or “Tr20x4-8H”. Add “-LH” for a left-hand thread.
Calculated live
Basic dimensions
- Major diameter
- 20.000 mm
- Pitch diameter
- 19.026 mm
- Minor diameter
- 18.376 mm
Tap drill · 75% thread
- Tap drill
- 18.75 mm (18.782 mm calculated)
- Clearance drill (normal)
- 21.00 mm (20.800 mm calculated)
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