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Probably a real stupid question but googling is not shedding any light so maybe not?

A cap head screw of size 40xM8x10. What is the diameter and length of the screw?

Diameter is 8mm obviously, length is 40mm? What the hell is the 10?

I've only ever seen screw sizes with two values, ie, M8x40

I can make a few guesses (diameter of head, height of head, thread length etc) but who knows if I'm guessing right?

Is this some convention that I'm missing?

Thanks

user34265
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    Where have you seen this written down? Sounds like there are 40 individual M8 x 10mm long screws in the assembly? – Jonathan R Swift Jul 23 '21 at 10:24
  • quantity, diameter, length, pitch. It's pretty rare to have pitch specified with x instead of - would be rare to do so in threads per cm so I doubt it's going for the finer 1 mm pitched M8. – Abel Jul 23 '21 at 11:47
  • thread pitch is missing – Pete W Jul 23 '21 at 15:47
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    If it is a hex head screw/bolt, 40 is the length, 10 is the hex size. – r13 Jul 23 '21 at 16:36
  • This is just a bad label. Engineering drawings are like any other form of communication. Clarity is what counts, not adherence to some arbitrary formatting rule. My best guess is that this is specifying 40 M8 screws that are 10mm long. – Drew Jul 24 '21 at 01:48
  • material: cap screw 40xM8x10 - quantity: 4. I can't work it out. Going to take a guess that it's the head diameter but seems an odd size for an M8? It's a super old drawing so no way of contacting the creator. I don't think it even matters, I was just curious as to what this means – user34265 Jul 25 '21 at 21:00

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If my memory is correct both the US and Metric bolts are graded with a number whereas the higher the number the stronger the bolt. Some of the more common metric grades are 5.8, 8.8, 10.9 and 12.9. This link will give you some help, and it explains sizing but not hardness. https://www.insight-security.com/get-to-know-metric-bolt-sizes I would guess the 10 stands for 10.9 as an abbreviation or its hardness is 10.9.

Gil
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