Ron, it's 5/16 BSC. I went to my old Domi-Racer box, picked the one you suggested and it was correct. I'm sure you're right about spinning the nut. I expect it will be slow careful going making sure it's properly threaded.

It's an ugly as sin jury-rig and it's slow and awkward. When I have access to a lathe I'll make a ring. Who knows? Maybe my gasket set will take so long that'll I have that done before it arrives. Thanks to this forum, I understood the real trick would be taking the spring pressure off the nut and holding the spring in place once the nut was released. Cheers!

email (option): moatjon [ at ] aol.com

This original BSA tool would not be to hard to copy,with a piece of tube the same dia,and a flat piece off steel or bar for the lever.

The 1946-58 list of BSA tools doesn't include this one, the more familiar clutch spring compressor tool is the one shown...

I've not seen this one before myself and wonder whether this is an aftermarket tool?...
BSA tools aren't usually marked with a description in this way, being identified by the part number and the illustration in the 'Service Tools' worksheet No.711....Ian

email (option): ian@wright52.plus.com

Yesterday I replaced the cleaned clutch plates with no issues. Piece of cake, really. My 5/16" bolt was a little bit shorter than ideal- I had to press the spring and nut in by hand to allow the long bolt to engage- but once that did I was able to hold the spring pressure away from the large nut enough to allow it to thread. It was surprisingly easy actually. As the large nut threaded down I simply had to periodically tighten the nut on the bolt a bit more to keep the spring pressure off.

It was made from a piece of soft steel strapping left over from a shelf unit. Bent on a vice and roughly shaped with a hacksaw. Very crude but it works.

email (option): moatjon [ at ] aol.com