Tap Drill Chart & Thread Reference

Tap Drill Chart & Thread Reference

Practical shop-floor reference for common cut-tap drill sizes. Select a target thread percentage, then compare the theoretical hole size to the nearest real standard drill.

What this tool shows:
  • Target theoretical drill size
  • Nearest standard drill size
  • Best practical drill match from the built-in list
  • Actual achieved thread percentage with that real drill

Imperial Threads (UNC / UNF)

Choose an imperial thread and desired thread percentage.

Metric Threads

Choose a metric thread and desired thread percentage.

Material Guidance

  • Aluminum: often fine in the 65–75% range
  • Mild steel: 70–75% is a practical starting point for a lot of work
  • Stainless / tougher materials: 60–70% often helps reduce torque and broken taps
  • Reality check: chip evacuation, tap style, coolant, and depth matter as much as chart math
Reference Only: This tool is intended as a general shop-floor reference for cut taps. The calculated size is theoretical. The suggested standard drill is the nearest common off-the-shelf drill size from the built-in list. Always verify critical applications against your print, tooling supplier data, and fit requirements before production use.
Built by Cinci CNC in Cincinnati, Ohio. Practical tooling and shop-floor solutions for real machining work.