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How long is the thread on a bolt?
Slimy38 - 4/5/14 at 04:28 PM

I'm currently looking to sort out my bolts (having failed to find anything other than stainless at Stoneleigh) but the sizes are proving difficult to find all in one place. Can anyone tell me how long is the threaded portion of a bolt, just so I can see if the next size up/down would work?

And I seem to remember that using fully threaded machine screws is frowned upon, is that correct?

coyoteboy - 4/5/14 at 04:41 PM

Depends if you're using metric or imperial, and they come in dozens of sizes, usually starting from about 2 diameters up to about 30 diameters, in steps of 5mm (metric). If you're using them for structural components you want the load carried through a shank rather than a threaded section wherever possible.

coyoteboy - 4/5/14 at 04:42 PM

I know they're stainless and you don't want stainless but checkout the sizes available here:

http://pts-uk.com

NTDWM but I use them at work.

Slimy38 - 4/5/14 at 04:51 PM

quote:
Originally posted by coyoteboy
Depends if you're using metric or imperial, and they come in dozens of sizes, usually starting from about 2 diameters up to about 30 diameters, in steps of 5mm (metric). If you're using them for structural components you want the load carried through a shank rather than a threaded section wherever possible.


OK, fair point. How about as an example using the M12 suspension bolts that are common to Haynes Roadsters? Is it worked on a percentage or is it a fixed value?

I like the principle of having the load on the shank, that makes sense.

Thanks for the pointer for the stainless, I'll bear that in mind. For now I'm mainly after the suspension bolts.


[Edited on 4/5/14 by Slimy38]

40inches - 4/5/14 at 05:51 PM

A chart here

Slimy38 - 4/5/14 at 06:18 PM

quote:
Originally posted by 40inches
A chart here


Perfect, thanks! I knew it would be somewhere, I just couldn't think of the appropriate Google search!

JC - 5/5/14 at 06:08 AM

About 7 posts..........

I'll get my coat!

mcerd1 - 5/5/14 at 07:50 AM

quote:
Originally posted by Slimy38
quote:
Originally posted by 40inches
A chart here


Perfect, thanks! I knew it would be somewhere, I just couldn't think of the appropriate Google search!

but keep in mind that there are several standards for metric bolts - all slightly different to each other
often its just the tolerances they are made to that change, but sometimes it the thread lengths, head sizes or even the pitch....

BS and DIN (british and german) standards are both quite common and fairly similar to each other but are being replaced by ISO (international) standards at the moment and most metric stainless bolts have always been to ISO spec's

e.g. we still use BS4190 bolts at work, but we are being forced to move onto ISO 4014 ones now...


any good bolt supplier should be able to tell you which spec they are made to and in what grade - and once you know the standard a quick google search will give you a table like the one in the link above

if they can't tell you what standard they are made to then I'd assume they are cheap chinese knockoffs and I wouldn't trust them

ps - any good bolt supplier will be able to get / make you bolts with a range of thread lengths
alot of them supply bolts with thread lengths that are 1.5*diameter or 2*diameter+6mm


[Edited on 6/5/2014 by mcerd1]

[Edited on 6/5/2014 by mcerd1]

coyoteboy - 6/5/14 at 07:48 AM

As above.

My normal suggestion is "find a supplier and work with what they have" as it'll bite you in the ass if you think you can buy "standard" fastener lengths! (I speak from experience, after electrical connectors, fasteners are by far the biggest pain in my ass from a design point of view!).

Slimy38 - 6/5/14 at 10:03 AM

Thanks for the replies. I found a couple of suppliers that used the DIN references so now I know what to look for I was able to get the full set. I bought the majority of bolts from one place, but the larger bolts for the lower rear wishbones had to come from elsewhere. They were all 8.8 DIN931 so fingers crossed they should be ok.

Now to find the nut covers for a decent price... I don't mind those being cheap Chinese knockoffs...

mcerd1 - 7/5/14 at 12:04 PM

^^ DIN931 will be fine, its more or less the same as the ISO4014 bolts

FYI both of those standards cover production grades A and B - basically grade A bolts are made with slightly better tolerances