Understanding Tap Hole Size Charts for Accurate Drilling

Hello everyone,

If you’ve ever stripped threads or struggled with loose fits, chances are the wrong tap hole size was the culprit. A tap hole size chart is your go-to reference for matching drill bit sizes to tap threads (metric or imperial). Using the correct size ensures proper thread engagement without excessive force.

For example, an M6 × 1.0 tap typically needs a 5.0 mm drill, while a ¼»-20 UNC tap calls for a #7 bit. Always check the chart before drilling—guesswork leads to broken taps or weak threads. Keep one handy in your toolbox for consistent, professional results.