What bolt/nut/screw do I need?

[ailwyn]

If I have a threaded fastener, how do I know what size it is if I can't find it documented?

I've come across thread gauges which could give me the pitch, but how do I know if it's an M10, M8 or whatever other variation?

[GeoffSmith]

M8 is 8mm across the thread. M10 is 10mm across the thread.

[ailwyn]

and does the length go from the bottom of the head to the tip or the full length of the bolt, or the length of the thread?

[nitroman]

The length is from the bottom of the head to the tip of the bolt, whether or not the entire shaft is threaded. It is perhaps simpler to say, measure the shaft only.

[GeoffSmith]

Bottom of the head to the tip.

[ailwyn]

Thanks both.

[algirdas]

Dear Ailwyn:

Check out this web page and the links contained in it.

http://www.boltdepot.com/fastener-infor ... eners.aspx

Real basic how-to stuff on measuring bolts and nuts.

Sincerely,

Algirdas

[ailwyn]

http://www.boltdepot.com/fastener-information/Identifying-Fasteners.aspx

Real basic how-to stuff on measuring bolts and nuts.

Highly recommended for anyone as bemused by fasteners as I am.