British Threads and bolt sizes.

[squarebob]

Ok guys, I picked up a Petter AA1 3.5 HP diesel engine. Cute little thing it is and I have no clue if it will run or not so the fun begins. My first problem is with bolt sizes. Not being familiar with thread types they use, I don't know how to spec replacement nuts and bolts I may need. A bunch of the bolts are very close to M8 fine thread but they are different. An M8 fine nut will go on about 1/2 way and then get tight so it is not metric threads I am dealing with. Can anyone educate me on the thread type I am dealing with here and have a source for replacement nuts and bolts here in the USA?

Thanks

Bob

[vdubnut62]

They could either be Whitworth or British standard, a copy of Machinery's handbook would be a great help to you.
Ron

[cgwymp]

Fasteners:
http://www.britishfasteners.com/

(I have no association with them except as a customer)

They'll sell you fasteners, tools, and a thread pitch gauge!

A whole bunch of thread info:
http://www.watchman.dsl.pipex.com/thread.html

EDIT: British thread info:
http://www.britishfasteners.com/threads/index.html

[squarebob]

Thanks, Just what I was looking for.

Bob

[Derb]

Hi Bob. Some of the older english engines I have torn down have BSF and/or BSW threads on them. Nothing else will substitute. Older landrovers/BMC vehicles use them also. cheers.

[squarebob]

The threads in question turn out to be 5/16 24 fine thread. They are on the head bolts, intake and exhaust studs, bolts holding on the rope starter casting to the flywheel and other location on the engine. This really baffled me.

Bob