Modding Nuts and bolt sizes... I don't get it

I want some nice nuts and bolts to replace the crappy plastic `pegs` that are currently holding my side panel window in place, I'm looking to get ones like this, but don't get the sizes

I want the threaded part to be 3mm diameter (for going through a 4mm hole), the length dosent matter because they can always be trimmed but 10mm would be ideal. On the screwfix website it just says

I assume that means
M8 = thread pitch?
20 = ?
10.9 = 10.9mm long?

What is the 20? is it the diameter of the threaded part? (I don't think it is because 20mm seems a bit big)

If anyone could find the bolts I want and the nuts to go with them, that would be great, otherwise any help about the sizes would be appreciated.

Thanks.

 

Lol, you're not alone! The number after the M is the outside diameter of the thread. As you need 3mm, you need M3 bolts. The correct usage of the number after the x is the thread pitch, but they have used this to indicate the thread length, ie 20mm long. i have no idea what the 10.9 is referring to, my only guess is that it could be the diameter of the head of the screw?

Here you go linky

edit - oh damn it, they are not domed, but countersunk, sorry!

edit2 - Try over here, yeah, that's better!

 

http://www.inoxfasteners.co.uk/measuring.htm

I must say i am very impressed with the quality of service and products from Inox.

ordered on monday bout 4pm and got it today (tuesday)

good prices, delivery is not bad as well.

use the link above as it explains all.


AW3K

 

Thanks guys, I'll take a look tomorrow because my sister is kicking me out of her room now and my computer is in peices spread across my bedroom floor

 

The 10.9 is referring to the strength of the bolt. 10.9 is a really strong bolt, like what you'd use in an engine. I believe it goes like 8.9, 9.9, 10.9, etc. Here, with the SAE hardware, we have 'grades'. Grade 3 being junk, on up to grade 8. Maybe higher, I dont know.

 

Nice one Marcello, I just took delivery of some grub screws. I checked the box, and sure enough, they state "cup point grade 14.9". That's another mystery sorted!

 

Anywhere else I might beable to get some from? the guy at inox isn't being very helpful at all

 

I just ran a quick search on google for "dome head cap screws" and it threw this one at me. No details about quantities, so may be worth giving them a ring. They have M3 size in the list though.

 

Gave them a call no-one answering the phone though so I fired off an e-mail to them

 

Also try looking for 'button head cap screws'. I normally go thru www.mcmaster.com or www.grainger.com but I'm not sure if they have UK distribution.

 

Persist with them, Supercool. Usually Inox Fasteners are really good and reliable.

 

I didn't like John from inox's attitude, so I got them from http://www.a2a4.co.uk/ 8p each