Size picker · Hex socket drive · DIN 912
Socket cap screw sizes.
The workhorse of machine building: a cylindrical head, an internal hex drive, and high-tensile steel — usually grade 12.9 in black. Pick a diameter and length below for the head diameter, head height and the Allen key it takes, with the screw drawn to proportion in the finish you're after.
1 Pick a diameter
2 Pick a length
Choose a diameter first.
Your browser could not draw the 3D view. The dimensions beside it are unaffected.
Drawn to proportion from the standard dimensions. Illustration, not a photograph of the item.
Selected
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| Sym | Dimension | Value |
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Job stopped? Ring 01327 877577 and we'll check the stock while you're on.
Read the full DIN 912 size chart
| Size | 2 | 2.5 | 3 | 4 | 5 | 6 | 8 | 10 | 12 | 14 | 15 | 16 | 18 | 20 | 22 | 25 | 28 | 30 | 32 | 35 | 38 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 | 85 | 90 | 95 | 100 | 105 | 110 | 115 | 120 | 125 | 130 | 140 | 145 | 150 | 155 | 160 | 165 | 170 | 175 | 180 | 185 | 190 | 195 | 200 | 210 | 220 | 230 | 240 | 250 | 260 | 270 | 280 | 290 | 300 |
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| M2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M2.5 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M4 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M5 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M6 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M8 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M10 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M12 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M14 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M16 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M18 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M20 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M22 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M24 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M27 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| M30 |
The range shown is what fastener wholesalers commonly list — not a claim about what the standard mandates, and not a stock list. In-between lengths (85, 95, 170…), lengths past 300mm and odd diameters like M7 are made too, and availability varies by finish and grade — ask us for anything you can't see.
Why cap screws are the machine-shop default
The head is small enough to counterbore flush, the internal drive can't slip a spanner, and the standard class is 12.9 — half as strong again as an 8.8 hex bolt. Published DIN 912 tables give the threaded length as 2d + 12, and shorter screws are threaded right to the head; on the long lengths at the end of the range, check the thread length with us rather than assuming the formula holds.
We also stock M1.6 and imperial socket caps that are not on this chart, and lengths past 300mm — ask us.
Need a shallower head for tight clearances? See low head cap screws. For a domed finish, button heads.
Not sure which you need?
Bring the old one in, or send us a photo. We are on Baird Close in Daventry with socket screws in black high-tensile, zinc and stainless across the common sizes.
More size charts
Every size, drawn to scale.
Hex setscrews
DIN 933 · full thread
Hex bolts
DIN 931 · part thread
Low head cap screws
DIN 7984
Button head screws
ISO 7380-1
Flanged button heads
ISO 7380-2
Countersunk socket screws
DIN 7991
Grub screws
DIN 913–916 · five points
Nuts
DIN 934 · nyloc · thin · Stover · flange
Washers
ISO 7089 · BS 4320 · penny
Not sure what the markings on the head mean? Bolt grades explained covers 8.8, 10.9, 12.9, stainless A2 and A4, and the imperial SAE grades.
All of it comes off the shelf at Baird Close — see the full fasteners & fixings range, or every size guide.