Forgive me if this post isn't news but its been a while since I tinkered with bikes so I'm posting anything I find useful. Had to hacksaw off four non standard bolts from the rear frame. They were supplied by whatever company sold the back rest they were holding on. I needed to replace them but had no idea of the size or thread pitch, the standard Yamaha bolts would of course be too short - Then I discovered this handy little gauge. I think its self explanatory.

Bolt sizes/threads (external) are easy enough to measure with just a steel rule (larger sizes) or a Vernier gauge, pitch gauges are useful for internal threads where you can't get a rule or vernier into them, the ones on that gauge are only any good for external threads though.

Still a useful gauge for quickness though.

Point taken Campaman however . . . . my problem was I didn't know the size of the internal thread but finding a bolt that fitted and measuring its external thread with the gauge gave me the answer. In essence, I used one to find the other.
 

Sorry no criticism meant, my business manufactures nuts so I am always keen to educate and help with threads :-)

None taken. Its been over 35 years since I last stripped an engine and I'm learning, or relearning as I go alone. If something strikes me as useful I'll post it knowing that it's probably old hat to many or alternatively someone will guide me in another direction. Its forums like this that pool knowledge and boy was I pleased to find it. All opinions and advice welcome.