M18x2 Thread Specs
Standard: ISO 261 (ISO Metric Fine)
This reference guide outlines the technical dimensions and tapping parameters for the standard M18x2 metric thread.
Part of the ISO Metric Fine series defined by ISO 261, the thread features a nominal diameter of 18 mm and a pitch of 2 mm.
For machining or fabrication, the recommended tap drill size is 16 mm (for 75% thread depth) or 16.12 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
18 mm
Pitch
2 mm
Threads per mm
0.5
Major Diameter
18 mm
Pitch Diameter (d₂)
16.701 mm
Minor Diameter (d₁) Ext
15.835 mm
Minor Diameter (D₁) Int
16.124 mm
Thread Height
1.732 mm
Root Radius
0.289 mm
Drilling & Strength Specs
Tap Drill (75%)
16 mm
Tap Drill (65%)
16.12 mm
Stress Area
204.18 mm²
Stress Diameter
15.546 mm
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Frequently Asked Questions
What is the tap drill size for a M18x2 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M18x2 is 16 mm. For a slightly looser 65% thread engagement, a 16.12 mm drill bit is recommended.
What is the pitch of a M18x2 thread?
The thread pitch for a standard M18x2 thread is 2 mm, which equates to approximately 0.5 threads per millimeter.
What are the major and pitch diameters for M18x2?
The nominal major diameter of M18x2 is 18 mm. The calculated pitch diameter (d₂) is 16.701 mm per the ISO 68-1/ISO 261 standards.