M33 Thread Specs
Standard: ISO 261 (ISO Metric Coarse)
This reference guide outlines the technical dimensions and tapping parameters for the standard M33 metric thread.
Part of the ISO Metric Coarse series defined by ISO 261, the thread features a nominal diameter of 33 mm and a pitch of 3.5 mm.
For machining or fabrication, the recommended tap drill size is 29.5 mm (for 75% thread depth) or 29.72 mm (for 65% thread depth).
Dimensional Specifications (mm)
Nominal Diameter
33 mm
Pitch
3.5 mm
Threads per mm
0.29
Major Diameter
33 mm
Pitch Diameter (d₂)
30.727 mm
Minor Diameter (d₁) Ext
29.211 mm
Minor Diameter (D₁) Int
29.716 mm
Thread Height
3.031 mm
Root Radius
0.505 mm
Drilling & Strength Specs
Tap Drill (75%)
29.5 mm
Tap Drill (65%)
29.72 mm
Stress Area
693.55 mm²
Stress Diameter
28.706 mm
Recommended Tightening Torque
| Property Class | Dry (Nm) | Lubricated (Nm) |
|---|---|---|
| Class 8.8 | 2390 | 1792.5 |
| Class 10.9 | 3515 | 2636.3 |
| Class 12.9 | 4218 | 3163.5 |
Quick Unit Converter
mm
⇄
inch
Frequently Asked Questions
What is the tap drill size for a M33 thread?
For standard thread engagement (approx. 75%), the recommended tap drill size for M33 is 29.5 mm. For a slightly looser 65% thread engagement, a 29.72 mm drill bit is recommended.
What is the pitch of a M33 thread?
The thread pitch for a standard M33 thread is 3.5 mm, which equates to approximately 0.29 threads per millimeter.
What are the major and pitch diameters for M33?
The nominal major diameter of M33 is 33 mm. The calculated pitch diameter (d₂) is 30.727 mm per the ISO 68-1/ISO 261 standards.