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Newbie Bolt Query
EasyJimbo - 27/4/09 at 10:44 AM

Hi All

Looking to order some bolts from my MK project, a silly question but when they refer to M5 bolts, does the 5 part refer to 5mm. I am after some 5,6, 8, 10 and 12mm bolts.
thanks
James

Mr Whippy - 27/4/09 at 10:46 AM

the bolt thread is 5mm in diameter for an M5

here's a nice little thing about threads - linky

[Edited on 27/4/09 by Mr Whippy]

Steve Hignett - 27/4/09 at 10:47 AM

Yes, and the clue is in the "M" bit - it refers to it being a "Metric" measurement. So M5 is 5mm, M6 is 6mm and so on...

You will prob want a selection of different lengths and also a selection of different "heads". For eg - an M5 DOME HEADED bolt for trim panels etc.

ATB

nick205 - 27/4/09 at 10:49 AM

the M number refers to the bolts diameter - e.g. an M5 bolt will have a Ø5mm body/thread.

Typically you specify bolts by diameter then length - e.g. M5x50 will be a Ø5mm x 50mm long bolt.

Also be aware that "bolts" are not threaded along their full length so you need to check what you're bolting together to make sure you have the right amount of thread.

"Set screws" on the other hand are threaded along their full length from head to tip. Again you need to be aware of what you're fixing together.

HTH

[Edited on 27/4/09 by nick205]

EasyJimbo - 27/4/09 at 11:23 AM

Thanks for the help guys. For areas such as suspension etc what should the bolt be, if not stainless?
thanks
james

Mr Whippy - 27/4/09 at 11:47 AM

quote:
Originally posted by EasyJimbo
Thanks for the help guys. For areas such as suspension etc what should the bolt be, if not stainless?
thanks
james


as above, no stainless on the suspension, use 8.8 (marked on the head of the bolt, don't use any that are not marked!) or above in carbon steel, see this table - table linky



[Edited on 27/4/09 by Mr Whippy]

iank - 27/4/09 at 12:13 PM

On sizing see http://www.namrick.co.uk/boltspec.asp

I'd stick only to 8.8 on suspension, the 'better' grades are also more brittle in nature so if they do go they go with a bang rather than stretching/bending, conversely if they don't go then the brackets will almost certainly be ripped off (being the weakest link in the chain) leaving a much bigger repair bill.

While the distinction between bolt and set screw can be important, a lot of people who sell them don't seem to know the difference and get confused.

I got some mixed bags from Namrick http://www.namrick.co.uk/browse.asp?PCID=14 to start off my collection.

Don't buy bolts from B&Q they are probably fine for putting up a gate but not for a car IMO. If you want cheap Screwfix sell 8.8, 10.9 and 12.9 bolts/set screws for not much money.