#10-32 Tap Drill — #21
The recommended tap drill for a #10-32 thread is #21. Thread engagement: ~75%.
Result
Answer
#21 drill bit (0.159")
Standard
Thread#10-32 UNF
TPI32
Tap Drill#21
Decimal Equivalent0.159"
Thread Engagement~75%
For a #10-32 UNF thread (32 TPI), use a #21 drill bit (0.159" decimal). This targets approximately 75% thread engagement, which is the standard recommendation for most applications.
Note
Reference value from published fastener data. Always verify with the fastener manufacturer for critical applications.
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About #10-32 Tap Drill
For a #10-32 UNF thread (32 TPI), the recommended tap drill size is #21 (0.159" decimal). This produces approximately 75% thread engagement, which is the industry standard for most applications. Always use a sharp HSS or cobalt drill bit and proper cutting fluid when tapping.