Example designation
0.5-10-ACME-4G
- 0.5
- Nominal major diameter in inches.
- 10
- Threads per inch; adjacent threads are 0.1000 in apart.
- ACME
- Acme thread form.
- 4G
- Class 4 general-purpose fit.
Start with the Acme form
GEN uses general-purpose G classes, STUB uses the shallower stub form with class 2, and CEN uses centralizing C classes. Changing the form changes the available fit choices.
Pitch is the spacing; lead is the travel
For multiple starts, lead equals pitch multiplied by the number of starts. Keep the TPI based on adjacent thread spacing, then choose the start count to obtain the intended travel per revolution.
Check the engaged length
The default engagement is twice the nominal diameter. Enter the actual engagement when it differs, and review the resulting allowance and pitch-diameter limits before choosing machining targets.