Metric Cutting-Tap Pilot Estimate
Subtract pitch from nominal metric diameter for a simple cutting-tap pilot-hole estimate. It is a rule of thumb, so compare the result with the sourced chart and the tap manufacturer’s recommendation before production.
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The M8 × 1.25 reference-chart row is 6.75 mm (17/64 in); a shop’s chosen drill can differ with the tap and process.
