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Grade C Hex Nut Dimensions (ISO 4034, M5 to M64)
Guide · Updated October 28, 2026
ISO 4034 covers hexagon regular nuts (style 1), product grade C, M5 to M64. This chart shows the preferred threads. Values agree across the ISO 4034:2012 published table and globalfastener (DIN EN ISO 4034:2012). s max is nominal; e is minimum.
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Step by step
- Find the thread: Pick the row for your thread size, M5 to M64.
- Pick the spanner: Use s for the wrench size, e.g. 24 mm for M16.
- Check the height: Grade C nuts vary more in height; allow for m max when checking bolt protrusion.
- Match the bolt: Pair with grade C bolts (ISO 4016) or screws (ISO 4018) of the same thread.
ISO 4034 grade C hex nut dimensions (mm)
Columns: thread D, pitch P, width across flats s max and min, width across corners e min, nut height m max and min.
- Size | P | s max | s min | e min | m max | m min
- M5 | 0.8 | 8 | 7.64 | 8.63 | 5.6 | 4.4
- M6 | 1 | 10 | 9.64 | 10.89 | 6.4 | 4.9
- M8 | 1.25 | 13 | 12.57 | 14.2 | 7.9 | 6.4
- M10 | 1.5 | 16 | 15.57 | 17.59 | 9.5 | 8
- M12 | 1.75 | 18 | 17.57 | 19.85 | 12.2 | 10.4
- M16 | 2 | 24 | 23.16 | 26.17 | 15.9 | 14.1
- M20 | 2.5 | 30 | 29.16 | 32.95 | 19 | 16.9
- M24 | 3 | 36 | 35 | 39.55 | 22.3 | 20.2
- M30 | 3.5 | 46 | 45 | 50.85 | 26.4 | 24.3
- M36 | 4 | 55 | 53.8 | 60.79 | 31.9 | 29.4
- M42 | 4.5 | 65 | 63.1 | 71.3 | 34.9 | 32.4
- M48 | 5 | 75 | 73.1 | 82.6 | 38.9 | 36.4
- M56 | 5.5 | 85 | 82.8 | 93.56 | 45.9 | 43.4
- M64 | 6 | 95 | 92.8 | 104.86 | 52.4 | —
Worked example: M16 grade C nut
An M16 ISO 4034 nut takes a 24 mm spanner and is 14.1 to 15.9 mm tall. Allow for the 15.9 mm maximum plus at least a thread or two of bolt protrusion when choosing bolt length.
Common problems
- Bolt too short: grade C nuts can be taller than ISO 4032; check m max.
- Socket slips: wide flat tolerance (e.g. M24 s 35 to 36 mm); use a good six-point socket.
- Mixed grades: grade C nuts are for general work; use ISO 4032 grade A/B for precision joints.
FAQ
ISO 4034 vs ISO 4032?
Same flats s, but grade C nuts have wider tolerances and a different height range (e.g. M12 m 10.4 to 12.2 mm vs 10.37 to 10.8 for ISO 4032). They are for general and structural work, not precision assemblies.
What does product grade C mean?
The widest tolerance grade in ISO 4759-1 (grades A, B, C).
Is there a DIN equivalent?
It is published as DIN EN ISO 4034, identical to ISO 4034:2012.
Why is M64 m min a dash?
The ISO table gives 49.4 mm and a second source 49.1 mm, so the cell is left blank.
Related guides and calculators
- Grade C hex bolts (ISO 4016)
- Hex nuts (ISO 4032)
- Hex head bolts (ISO 4014)
- Hex head screws (ISO 4017)
- All free machinist calculators
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