This is a manufacturer recommendation in the reviewed dataset. The major-minus-pitch estimate gives 0.2000 inch, which explains why the nearby #7 drill is a common selected size without claiming the estimate is a standard value.
Calculation cross-check
Nominal major diameter is 0.2500 inch. One pitch at 20 TPI is 0.0500 inch. Subtracting gives a 0.2000-inch approximation; the reviewed lookup selects the #7 drill at 0.2010 inch.
Before tapping
Confirm that the tap is a cutting tap, secure the work, keep the drill aligned, and use cutting practice appropriate to the material. Gauge the thread when fit matters.
Important limitation
A forming tap generally needs a larger hole. Use the forming-tap maker’s chart rather than this cut-tap value.
A forming tap generally needs a larger hole. Use the forming-tap maker’s chart rather than this cut-tap value.
Technical references
- Cle-Line C01112 Tap and Drill Recommendations — Greenfield Industries / Cle-Line. Accessed 2026-11-09.
- NASA Robotics Alliance Project Design Guide, Appendix C — Hole Size Charts — NASA Robotics Alliance Project. Accessed 2026-11-10.
Standards references identify scope and terminology; protected dimensional tables are not reproduced.