NPT Tap Drill Sizes When tapping NPT threads, the drill size determines the minor diameter of the internal thread. Because NPT threads are tapered, the drill creates a straight hole that the tapered tap gradually engages — you’ll get full threads near the entrance and partial threads at depth. NPT Size TPI Tap Drill (in) … Read more
Metric Tap & Clearance Drill Sizes This table covers standard coarse pitch metric threads (the default — if a drawing says “M10” without specifying pitch, it means M10×1.5 coarse). For each thread size, you get the tap drill (for cutting internal threads) and clearance drill (for a bolt to pass through freely). Thread Pitch (mm) … Read more
UNF Tap Drill Sizes UNF (Unified National Fine) threads have more threads per inch than UNC for the same diameter. They’re stronger in thin-walled parts, provide finer adjustment, and resist vibration loosening better — but they’re less forgiving and easier to cross-thread. Thread Size TPI Tap Drill Decimal (in) 75% Thread Clearance Drill #0-80 80 … Read more
UNC Tap Drill Sizes UNC (Unified National Coarse) is the default thread series in the US. If a drawing says “1/2-13” — that’s UNC. Coarse threads are stronger, more forgiving of dirty conditions, and easier to assemble than fine threads. Thread Size TPI Tap Drill Decimal (in) 75% Thread Clearance Drill #1-64 64 #53 0.0595 … Read more