Set Up Tapping
Choose metric or imperial, then enter major diameter and pitch (or TPI for inch threads).
Tap Drill Size Calculator
Estimate a starting tap drill size from thread major diameter and pitch.
Metrik MFG / TappingREADY
Tap Drill Size Calculator
INPUTVALUEOUTPUT
Primary input01
Process setting02
Calculated output03
CALCULATION STATUSREADY TO CALCULATEEnter values below to generate results
STANDARD MODE
READY TO CALCULATE
Tap Drill Size Calculator
Advanced Engineering
PRACTICAL CONTEXT
Using the result in real shop work
A tap drill needs to leave enough material for the thread while avoiding excessive torque. This calculator provides the common starting relationship for metric and inch threads.
Where This Result Helps
Use the result as a starting shop reference and verify the final drill from the tap manufacturer or approved thread chart.
What Can Distort the Result
Treating the estimate as a universal drill chart, entering pitch in the wrong unit, or ignoring thread percentage requirements.
ENGINEERING METHOD
How the tapping calculation works.
FORMULAMetric starting drill ≈ major diameter − pitch. Imperial starting drill ≈ major diameter − (1 ÷ TPI). The relationships are practical starting estimates, not universal thread charts.
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