Example designation
Tr12 x 2-7e
- Tr
- Metric trapezoidal thread form.
- 12
- Nominal major diameter of 12 mm.
- 2
- Pitch of 2 mm for this single-start example.
- 7e
- Pitch-diameter grade 7 at external position e.
Set the pitch-diameter tolerance
Pitch grades 7, 8, and 9 are available. External positions c and e pair with internal position H; the diameter grades remain fixed at 4 in this calculator.
For a screw with several starts
Enter the spacing between adjacent threads as pitch. The start count sets the lead and helix angle, which also affect measurement over wires. Confirm the complete lead-and-pitch callout when documenting the part.