M27 Thread Specs
Standard: ISO 261 (ISO Metric Coarse)
This reference guide outlines the technical dimensions and tapping parameters for the standard M27 metric thread.
Part of the ISO Metric Coarse series defined by ISO 261, the thread features a nominal diameter of 27 mm and a pitch of 3 mm.
For machining or fabrication, the recommended tap drill size is 24 mm (for 75% thread depth) or 24.19 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
27 mm
Pitch
3 mm
Threads per mm
0.33
Major Diameter
27 mm
Pitch Diameter (d₂)
25.051 mm
Minor Diameter (d₁) Ext
23.752 mm
Minor Diameter (D₁) Int
24.185 mm
Thread Height
2.598 mm
Root Radius
0.433 mm
Drilling & Strength Specs
Tap Drill (75%)
24 mm
Tap Drill (65%)
24.19 mm
Stress Area
459.41 mm²
Stress Diameter
23.319 mm
Recommended Tightening Torque
| Property Class | Dry (Nm) | Lubricated (Nm) |
|---|---|---|
| Class 8.8 | 1300 | 975 |
| Class 10.9 | 1912 | 1434 |
| Class 12.9 | 2294 | 1720.5 |
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Frequently Asked Questions
What is the tap drill size for a M27 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M27 is 24 mm. For a slightly looser 65% thread engagement, a 24.19 mm drill bit is recommended.
What is the pitch of a M27 thread?
The thread pitch for a standard M27 thread is 3 mm, which equates to approximately 0.33 threads per millimeter.
What are the major and pitch diameters for M27?
The nominal major diameter of M27 is 27 mm. The calculated pitch diameter (d₂) is 25.051 mm per the ISO 68-1/ISO 261 standards.