M68x4 Thread Specs
Standard: ISO 261 (ISO Metric Fine)
This reference guide outlines the technical dimensions and tapping parameters for the standard M68x4 metric thread.
Part of the ISO Metric Fine series defined by ISO 261, the thread features a nominal diameter of 68 mm and a pitch of 4 mm.
For machining or fabrication, the recommended tap drill size is 64 mm (for 75% thread depth) or 64.25 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
68 mm
Pitch
4 mm
Threads per mm
0.25
Major Diameter
68 mm
Pitch Diameter (d₂)
65.402 mm
Minor Diameter (d₁) Ext
63.67 mm
Minor Diameter (D₁) Int
64.247 mm
Thread Height
3.464 mm
Root Radius
0.577 mm
Drilling & Strength Specs
Tap Drill (75%)
64 mm
Tap Drill (65%)
64.25 mm
Stress Area
3241.89 mm²
Stress Diameter
63.093 mm
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Frequently Asked Questions
What is the tap drill size for a M68x4 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M68x4 is 64 mm. For a slightly looser 65% thread engagement, a 64.25 mm drill bit is recommended.
What is the pitch of a M68x4 thread?
The thread pitch for a standard M68x4 thread is 4 mm, which equates to approximately 0.25 threads per millimeter.
What are the major and pitch diameters for M68x4?
The nominal major diameter of M68x4 is 68 mm. The calculated pitch diameter (d₂) is 65.402 mm per the ISO 68-1/ISO 261 standards.