Interactive calculator
Tap Drill Size Calculator
Select the full thread designation and tapping process. Results show the source context, units and limits that matter to the choice.
Methodology
Straight-thread cutting results are manufacturer lookups. Forming results appear only where a maker publishes a reviewed pre-hole range. NPT recommendations stay tied to their tooling context because Cle-Line and Travers publish different values for 1/8-27 NPT. No straight-thread formula is applied to pipe threads.
Inputs and assumptions
- Thread family and complete designation
- Cutting versus forming process
- Named manufacturer context
Always verify the exact tap maker’s current data for the tool, work material and required thread class.