Thread size chart
Look up standard thread sizes, convert TPI and pitch, and calculate synchronized feed for single-point threading on the lathe.
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What it covers
- Pitch (mm) = 25.4 ÷ TPI
- Major, minor and pitch diameters for common classes
- Multi-start lead and synchronized feed
- Spindle and machine feed ceilings applied
Common questions
- How do I convert TPI to pitch?
- Divide 25.4 by the threads per inch. 20 TPI = 1.27 mm pitch.
- What is lead on a multi-start thread?
- Lead = pitch × number of starts. Threading feed per revolution equals the lead.