Drill Bits / #29 Diameter
8-32 Tap Drill Size is a #29 Drill Bit
For an 8-32 UNC tap, use a #29 drill bit with a 0.1360" hole diameter, equal to 3.45mm.
Correct Drill Bit Size for an 8-32 Tap
The correct drill bit size for an 8-32 & 8-36 tap is a #29 drill bit. A #29 drill measures 0.1360" or 3.45mm, making it the proper tap drill size for 8-32 UNC internal threads.
Using a #29 Drill Before Tapping
Drill the hole with a #29 drill bit before running the tap. This size is also commonly used for 8-36 tap drill applications, so it is a useful number drill size for #8 machine screw thread work.
8-32 Hole Size and Thread Engagement
The 0.1360" hole size leaves enough material for the tap to cut clean, usable threads without making the hole unnecessarily tight. This helps maintain proper thread engagement while reducing stress on the tap during machining, repair, or maintenance work.
Why the Correct Tap Drill Size Matters
Choosing the correct tap drill size helps improve tapped-hole consistency, fastener fit, and tool life. In production environments, using the correct #29 drill size for 8-32 UNC threads can reduce broken taps, oversized threads, and rejected parts.
Additional Drill and Tap Size References
Use the chart links below to compare nearby number drill sizes, standard tap drill charts, metric tap drill charts, and other drill size references when selecting hole sizes for production or repair work.
Find Complete Tap and Drill Charts
Additional tap and drill resources are available for machinists, maintenance personnel, and industrial users.
