How do I tell what pitch a bolt is?

[orange71]

I need to find replacement bolts for my AMP forks. I have no idea what pitch they are - how do I tell so I can source replacements? 2 fell out from the forks - there are some bolts remaining so I can do measurements if someone tells me what I need to measure!!

 

[ededwards]

Although I'm sure there are more scientific methods I'd suggest taking one of the remaining bolts to a hardwear store (preferably the old school type that sell bolts by the piece rather than Focus/B&Q) and using the right size nut they'll be able to work out the pitch and give you new bolts pretty easily.

 

[orange71]

cheers (now to find old-school hardware store... :roll: )

 

[kaiser]

What measuring devices do you have? Vernier? Best ways to determine type of bolt are outer diameter and TPI(threads per inch) ideally you would also need a zeus book to look up the info.

 

[DebtMan]

Or....look for a pitch gauge on fleabay. I got one for less than a fiver.

Have a look: http://search.ebay.co.uk/search/search. ... itch+gauge

 

[Andy R]

You just need one of these thread gauges.

For most bike stuff (apart from bottom bracket threads) you need a metric one. (as thats what most of the threads are).

Use vernier calipers or a micrometer to measure the major diameter and use the gauge to determine the pitch.
Available from any engineering suppliers or, of course, the interweb !!

If you need to know tapping drill sizes etc. then, yes - a Zeus book is the way to go :!:

 

[crogthomas]

threads

Hold a ruler against the side of the thread and count the number of threads within a certain length. For example if there are 10 threads within a 10mm length the pitch is 1mm. If there are 10 threads in 8mm then the pitch is 0.8mm. The longer length you can use the better since it makes it a bit easier.
i.e. the length divided by the thread count is the pitch:

Length/ThreadCount = Pitch

 

[doogie]

Hello Ed,
As I am an engineer by trade I have verniers,micrometers and thread pitch gauges in my toolbox at work, I have also got a zeus book.
We have also got a good selection of nuts and bolts at work.
Let me know if you need any help sourcing some bolts and I may be able to help you out mate.
Cheers,
Ian. doogie.

 

[dekerfintheshed]

Ditto, we've got all the kit at my place and I'm a mech' engineer too so have access to old blokes in small rooms with micrometers, thread gauges etc plus a maintenance dept that have all sorts of bolts, capscrews etc...

 

[orange71]

thanks guys since doogie was in there first and lives slightly closer I'll see what he can do - if not then I'll come to you next, thanks!