M80 Thread Specs
Standard: ISO 261 (ISO Metric Coarse)
This reference guide outlines the technical dimensions and tapping parameters for the standard M80 metric thread.
Part of the ISO Metric Coarse series defined by ISO 261, the thread features a nominal diameter of 80 mm and a pitch of 6 mm.
For machining or fabrication, the recommended tap drill size is 74 mm (for 75% thread depth) or 74.37 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
80 mm
Pitch
6 mm
Threads per mm
0.17
Major Diameter
80 mm
Pitch Diameter (d₂)
76.103 mm
Minor Diameter (d₁) Ext
73.505 mm
Minor Diameter (D₁) Int
74.371 mm
Thread Height
5.196 mm
Root Radius
0.866 mm
Drilling & Strength Specs
Tap Drill (75%)
74 mm
Tap Drill (65%)
74.37 mm
Stress Area
4344.05 mm²
Stress Diameter
72.639 mm
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Frequently Asked Questions
What is the tap drill size for a M80 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M80 is 74 mm. For a slightly looser 65% thread engagement, a 74.37 mm drill bit is recommended.
What is the pitch of a M80 thread?
The thread pitch for a standard M80 thread is 6 mm, which equates to approximately 0.17 threads per millimeter.
What are the major and pitch diameters for M80?
The nominal major diameter of M80 is 80 mm. The calculated pitch diameter (d₂) is 76.103 mm per the ISO 68-1/ISO 261 standards.