Machining - brunius.me

Tap Drill Chart

I got sick of online tap drill charts giving you weird numbers for stuff. So I made my own!
The 100% - 50% columns correspond to thread engagement - how much of the thread is in contact with the material.

• For most purposes, use 75%.
• In plastic (and other soft materials), 100% can provide great strength.
• 50% will be easier to tap, and is what you should use in tougher materials (eg steel).
  If it's a hole with depth at least 2 x diameter, you can use this to make it easier to tap, without giving up most of the strength.

TapDrillMath.ods