Threads / Size reference

M20x1.5 Metric fine

M20x1.5 has a nominal outside diameter of 20 mm and a 1.5 mm pitch.

Nominal major diameter20 mm

0.787402 in

Pitch1.5 mm

16.933333 TPI · calculated

Check tap-drill options →Compare M20x2 →

Nominal dimensions; no class allowances or acceptance limits applied. M sizes state diameter and pitch in millimetres.

M20x1.5 · PITCH VIEWSCHEMATIC

same diameter comparison

M20x1.5 vs M20x2

M20x2 Metric fine shares the nominal diameter but has a 2.000000 mm pitch. The pitch difference is 0.500000 mm; these are different nominal threads.

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Nominal size comparison
Property	M20x1.5 Metric fine	M20x2 Metric fine
Nominal diameter · in	0.787402	0.787402
Nominal diameter · mm	20	20
Threads per inchDifferent	16.933333	12.7
Pitch · mmDifferent	1.5	2

All 3 options at this diameter

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Nominal thread sizes in this reference
Designation	Major Ø · in / mm	TPI	Pitch · mm	Drill evidence	Next step
M20x2.5 Metric coarse	0.787402 / 20	10.16 converted	2.5	Chart row	Tap-drill lookup →
M20x1.5 Metric fine	0.787402 / 20	16.933333 converted	1.5	Chart row	Tap-drill lookup →
M20x2 Metric fine	0.787402 / 20	12.7 converted	2	Equation only	Tap-drill lookup →

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Source chart available

Cutting-tap drill references

Cut taps · Guhring chart · PDF page 2
Target theoretical thread	Listed drill	Diameter · in / mm
55%	18.90 mm	0.744094 / 18.9
65%	18.75 mm	0.738189 / 18.75
75%	18.50 mm	0.728346 / 18.5

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Need acceptance limits?

The complete class and applicable drawing requirements are needed. These nominal values are not maximum/minimum inspection limits.

Part has no marking?

Measure the correct diameter and pitch, then compare candidates across metric and inch systems.

Basis for this size

Nominal designation and family transcribed from the live directory on 2026-10-19; unit conversions are calculated using exactly 25.4 mm/in. The drill row was read from Guhring PDF page 2; numbered and letter drill diameters use page 1. Paid standard limit tables have not been reviewed.

ISO 261 · metric general plan ↗ · Guhring · Tap Drill Sizes ↗ Full source scope →