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Thread & tap drill calculator

Find a tapping drill size from the thread, or look up supported threads by diameter and pitch.

How to use

Selections and dimensions

Calculation result

Thread sizeNominal diametermmPitchmmTap drill lower valuemmTap drill upper valuemm
M6 × 16155
M8 × 1.2581.256.86.8
M10 × 1.5101.58.58.5
M12 × 1.75121.7510.210.2
#10-24 UNC4.8261.058333.6833.937
1/4-20 UNC6.351.274.97845.2578
#10-32 UNF4.8260.793753.96244.1656
1/4-28 UNF6.350.907145.35945.588

Supported scopeM6 / M8 / M10 / M12 · #10-24 UNC / 1/4-20 UNC · #10-32 UNF / 1/4-28 UNF

Metric rows are manufacturer drill examples. UNC/UNF ranges apply to Gühring 4388/4389 cutting taps. Form taps, tapered pipe threads and other sizes are unsupported. Check tooling data for the material and thread engagement.

How to use

Search a thread name or enter diameter/pitch in mm; blank fields do not filter. Numeric matching is ±0.005 mm. Inch pitch is 25.4/TPI.

Example calculation

M8 × 1.25 → Ø6.8 mm; 1/4-20 UNC → Ø4.9784–5.2578 mm

Calculation method

Results use the stated subset of the sources below. Numerical conversions and limits are explicit.

P[mm] = 25.4 / TPI

Calculation limits

Metric rows are manufacturer drill examples. UNC/UNF ranges apply to Gühring 4388/4389 cutting taps. Form taps, tapered pipe threads and other sizes are unsupported. Check tooling data for the material and thread engagement.

Sources