Drill Bits / #21 Diameter
10-32 Tap Drill Size is a #21 Drill Bit
The correct 10-32 tap drill size is a #21 drill bit with a 0.1590" (4.04mm) hole diameter for 10-32 UNF threads.
Correct Tap Drill Size for 10-32 Threads
The recommended 10-32 tap drill size is a #21 drill bit, producing a hole diameter of 0.1590" (4.04mm) for 10-32 UNF threads. This size is widely used across machining and production environments to establish the correct starting point for thread cutting.
Choosing the Right Drill Bit for 10-32 Tapping
Using the correct drill bit size for a 10-32 tap ensures consistent thread formation and reduces cutting resistance during tapping. A #21 drill provides a balanced hole size that supports clean thread generation without excessive tool load.
10-32 Hole Size and Thread Fit
The 10-32 tap hole size directly influences thread engagement and fit. A properly sized hole allows the tap to cut accurate threads while maintaining strength and minimizing the risk of tool breakage. The standard 0.1590" hole diameter offers reliable results for most UNF applications.
Why Drill Size Matters in Production
In CNC machining, repair work, and general fabrication, selecting the correct 10-32 drill size improves repeatability, thread quality, and tool life. Shops working in metric environments can reference the equivalent size of 4.04mm when selecting tooling.
Browse Additional Drill Tap Charts
Compare standard, letter, number, and metric drill sizes to quickly find the correct tap drill for similar thread sizes and machining applications.
