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Grade C Hex Head Bolt Dimensions (ISO 4016, M5 to M64)
Guide · Updated October 28, 2026
ISO 4016 covers hexagon head bolts (partially threaded), product grade C, M5 to M64. This chart shows the preferred threads. Values agree across the ISO 4016:2022 published table and fasteners.eu. s max is nominal; e is minimum.
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Step by step
- Find the thread: Pick the row for your bolt, M5 to M64.
- Pick the spanner: Use s for the wrench size, e.g. 24 mm for M16.
- Check the head: Grade C heads vary more: use k max for clearance and k min for engagement.
- Read thread length: Use the b column for your bolt length range; a dash means that length range is not listed.
- Match the nut: Pair with grade C nuts (ISO 4034) of the same thread.
ISO 4016 grade C hex head bolt dimensions (mm)
Columns: thread d, pitch P, width across flats s max and min, width across corners e min, head height k max and min, thread length b (ref.) for l ≤ 125, 125 < l ≤ 200 and l > 200 mm.
- Size | P | s max | s min | e min | k max | k min | b ≤125 | b ≤200 | b >200
- M5 | 0.8 | 8 | 7.64 | 8.63 | 3.875 | 3.125 | 16 | 22 | 35
- M6 | 1 | 10 | 9.64 | 10.89 | 4.375 | 3.625 | 18 | 24 | 37
- M8 | 1.25 | 13 | 12.57 | 14.2 | 5.675 | 4.925 | 22 | 28 | 41
- M10 | 1.5 | 16 | 15.57 | 17.59 | 6.85 | 5.95 | 26 | 32 | 45
- M12 | 1.75 | 18 | 17.57 | 19.85 | 7.95 | 7.05 | 30 | 36 | 49
- M16 | 2 | 24 | 23.16 | 26.17 | 10.75 | 9.25 | 38 | 44 | 57
- M20 | 2.5 | 30 | 29.16 | 32.95 | 13.4 | 11.6 | 46 | 52 | 65
- M24 | 3 | 36 | 35 | 39.55 | 15.9 | 14.1 | 54 | 60 | 73
- M30 | 3.5 | 46 | 45 | 50.85 | 19.75 | 17.65 | 66 | 72 | 85
- M36 | 4 | 55 | 53.8 | 60.79 | 23.55 | 21.45 | — | 84 | 97
- M42 | 4.5 | 65 | 63.1 | 71.3 | 27.05 | 24.95 | — | 96 | 109
- M48 | 5 | 75 | 73.1 | 82.6 | 31.05 | 28.95 | — | 108 | 121
- M56 | 5.5 | 85 | 82.8 | 93.56 | 36.25 | 33.75 | — | — | 137
- M64 | 6 | 95 | 92.8 | 104.86 | 41.25 | 38.75 | — | — | 153
Worked example: M16 x 100 grade C bolt
An M16 x 100 ISO 4016 bolt takes a 24 mm spanner (s min 23.16 mm), has a 9.25 to 10.75 mm head and, since l ≤ 125, about 38 mm of thread. Plan head clearance for the 10.75 mm maximum.
Common problems
- Head too tall: grade C k max is above nominal; check clearance with k max.
- Socket slips: wide flat tolerance (e.g. M24 s 35 to 36 mm); use a good six-point socket.
- Thread runs out short: b depends on length range; check the right column.
- Mixed grades: use ISO 4014 grade A/B bolts for precision joints.
FAQ
ISO 4016 vs ISO 4014?
Same nominal flats, head height and thread length b, but grade C has wider tolerances. For M10, e min is 17.59 mm vs 17.77 mm for grade A, and k runs 5.95 to 6.85 mm.
ISO 4016 vs ISO 4018?
ISO 4016 bolts are partially threaded; ISO 4018 covers fully threaded grade C screws.
What does product grade C mean?
The widest tolerance grade in ISO 4759-1 (grades A, B, C).
Why are some b cells dashes?
The ISO table lists no thread length for that length range on that size.
Related guides and calculators
- Grade C hex nuts (ISO 4034)
- Hex head bolts (ISO 4014)
- Hex head screws (ISO 4017)
- All free machinist calculators
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