M39x3 Thread Specs
Standard: ISO 261 (ISO Metric Fine)
This reference guide outlines the technical dimensions and tapping parameters for the standard M39x3 metric thread.
Part of the ISO Metric Fine series defined by ISO 261, the thread features a nominal diameter of 39 mm and a pitch of 3 mm.
For machining or fabrication, the recommended tap drill size is 36 mm (for 75% thread depth) or 36.19 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
39 mm
Pitch
3 mm
Threads per mm
0.33
Major Diameter
39 mm
Pitch Diameter (d₂)
37.051 mm
Minor Diameter (d₁) Ext
35.752 mm
Minor Diameter (D₁) Int
36.185 mm
Thread Height
2.598 mm
Root Radius
0.433 mm
Drilling & Strength Specs
Tap Drill (75%)
36 mm
Tap Drill (65%)
36.19 mm
Stress Area
1028.39 mm²
Stress Diameter
35.319 mm
Quick Unit Converter
mm
⇄
inch
Frequently Asked Questions
What is the tap drill size for a M39x3 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M39x3 is 36 mm. For a slightly looser 65% thread engagement, a 36.19 mm drill bit is recommended.
What is the pitch of a M39x3 thread?
The thread pitch for a standard M39x3 thread is 3 mm, which equates to approximately 0.33 threads per millimeter.
What are the major and pitch diameters for M39x3?
The nominal major diameter of M39x3 is 39 mm. The calculated pitch diameter (d₂) is 37.051 mm per the ISO 68-1/ISO 261 standards.