The Mechanical
Engineering Handbook




ISO Metric Bolt Sizes and Dimensions

Size Chart



Thread Size Major Diameter (mm) Minor Diameter (mm) Thread Pitch (mm) Pitch Diameter (mm) Tapping Drill Diameter (mm) Clearance Hole Diameter (mm)
M1 1.0 0.729 0.25 0.838 0.75 1.3
M1.1 1.1 0.829 0.25 0.938 0.85 1.4
M1.2 1.2 0.929 0.25 1.038 0.95 1.5
M1.4 1.4 1.075 0.30 1.205 1.10 1.8
M1.6 1.6 1.221 0.35 1.373 1.25 2.0
M1.8 1.8 1.421 0.35 1.573 1.45 2.3
M2 2.0 1.567 0.40 1.740 1.60 2.6
M2.2 2.2 1.713 0.45 1.908 1.75 2.9
M2.5 2.5 2.013 0.45 2.208 2.05 3.1
M3 3.0 2.459 0.50 2.675 2.50 3.6
M3.5 3.5 2.850 0.60 3.110 2.90 4.2
M4 4.0 3.242 0.70 3.545 3.30 4.8
M4.5 4.5 3.688 0.75 4.013 3.80 5.3
M5 5.0 4.134 0.80 4.480 4.20 5.8
M6 6.0 4.917 1.00 5.350 5.00 7.0
M7 7.0 5.917 1.00 6.350 6.00 8.0
M8 8.0 6.647 1.25 7.188 6.80 10.0
M9 9.0 7.647 1.25 8.188 7.80 11.0
M10 10.0 8.376 1.50 9.026 8.50 12.0
M11 11.0 9.376 1.50 10.026 9.50 13.5
M12 12.0 10.106 1.75 10.863 10.20 15.0
M14 14.0 11.835 2.00 12.701 12.00 17.0
M16 16.0 13.835 2.00 14.701 14.00 19.0
M18 18.0 15.394 2.50 16.376 15.50 22.0
M20 20.0 17.294 2.50 18.376 17.50 24.0
M22 22.0 19.294 2.50 20.376 19.50 26.0
M24 24.0 20.752 3.00 22.051 21.00 28.0
M27 27.0 23.752 3.00 25.051 24.00 33.0
M30 30.0 26.211 3.50 27.727 26.50 35.0
M33 33.0 29.211 3.50 30.727 29.50 38.0
M36 36.0 31.670 4.00 33.402 32.00 41.0
M39 39.0 34.670 4.00 36.402 35.00 44.0
M42 42.0 37.129 4.50 39.077 37.50 47.0
M45 45.0 40.129 4.50 42.077 40.50 50.0
M48 48.0 42.857 5.00 44.752 43.00 53.0
M52 52.0 46.587 5.00 48.752 47.00 57.0
M56 56.0 50.046 5.50 52.428 50.50 61.0
M60 60.0 54.046 5.50 56.428 54.50 65.0
M64 64.0 57.505 6.00 60.103 58.00 69.0
M68 68.0 61.505 6.00 64.103 62.00 73.0

Definitions



Major Diameter: The largest diameter of a thread that dictates all metric bolt sizes.

Minor Diameter: The smallest diameter of a threaded element, also called the root of the thread.

Thread Pitch: The distance between two parallel crests on a thread.

Tapping Drill Diameter: The diameter of the drilled hole required before the tapping process can begin.

Clearance Hole Diameter Diameter: The diameter of the hole that allows the bolt or screw to pass through without actually engaging the threads.



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