Tap drill & clearance hole
Tap drill and clearance hole sizes for common UNC, UNF and metric threads, #4-40 through 3/4-10 and M3 through M16.
Tap drill & clearance hole
Tap drill sizes are for about 75% thread, which is what most shops run. Clearance is the normal fit.
Tap drill for about 75% thread: drill ≈ major dia − 0.975 · pitch (inch) or major − pitch (metric), rounded to the nearest stock drill.
Clearance is the normal fit from ASME B18.2.8, roughly major diameter plus 6% for small fasteners.
For cold-form (roll) taps the drill is larger; use the tap maker's chart. Die cast and molded parts get a cored hole with a lead-in per the caster's table.
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