M56 Thread Specs
Standard: ISO 261 (ISO Metric Coarse)
This reference guide outlines the technical dimensions and tapping parameters for the standard M56 metric thread.
Part of the ISO Metric Coarse series defined by ISO 261, the thread features a nominal diameter of 56 mm and a pitch of 5.5 mm.
For machining or fabrication, the recommended tap drill size is 50.5 mm (for 75% thread depth) or 50.84 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
56 mm
Pitch
5.5 mm
Threads per mm
0.18
Major Diameter
56 mm
Pitch Diameter (d₂)
52.428 mm
Minor Diameter (d₁) Ext
50.046 mm
Minor Diameter (D₁) Int
50.84 mm
Thread Height
4.763 mm
Root Radius
0.794 mm
Drilling & Strength Specs
Tap Drill (75%)
50.5 mm
Tap Drill (65%)
50.84 mm
Stress Area
2030.02 mm²
Stress Diameter
49.252 mm
Recommended Tightening Torque
| Property Class | Dry (Nm) | Lubricated (Nm) |
|---|---|---|
| Class 8.8 | 12500 | 9375 |
| Class 10.9 | 18375 | 13781.3 |
| Class 12.9 | 22050 | 16537.5 |
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Frequently Asked Questions
What is the tap drill size for a M56 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M56 is 50.5 mm. For a slightly looser 65% thread engagement, a 50.84 mm drill bit is recommended.
What is the pitch of a M56 thread?
The thread pitch for a standard M56 thread is 5.5 mm, which equates to approximately 0.18 threads per millimeter.
What are the major and pitch diameters for M56?
The nominal major diameter of M56 is 56 mm. The calculated pitch diameter (d₂) is 52.428 mm per the ISO 68-1/ISO 261 standards.