Metric, BSF/BSW, UNC and UNF Conversion Table

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The table below can be used to help find the nearest sized metric coarse, metric fine, british standard fine, british standard whitworth, unified coarse and unified fine fasteners.

Thread sizes are not directly interchangeable. For guidance only.

Metric CoarseMetric FineBSF/BSWUNCUNF
M2 x 0.4--1-641-72
M2.5 x 0.45--3-483-56
M3 x 0.5--4-404-48
M3.5 x 0.6--6-326-40
M4 x 0.7--8-328-36
M5 x 0.8--10-2410-32
M6 x 1M6 x 0.751/4"1/4-201/4-28
M8 x 1.25M8 x 15/16"5/16-185/16-24
M10 x 1.5M10 x 1.253/8"3/8-163/8-24
M12 x 1.75M12 x 1.251/2"1/2-131/2-20
M14 x 2M14 x 1.59/16"9/16-129/16-18
M16 x 2M16 x 1.55/8"5/8-115/8-18
M20 x 2.5M20 x 1.53/4"3/4-103/4-16
M24 x 3M24 x 21"1-81-12
M30 x 3.5M30 x 21-1/8"1 1/4-71 1/8-12
M36 x 4M36 x 31-3/8"1 1/2-61 1/4-12

* Calculated with: HB = 0,95 · HV

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