7 replies to this topic

[bmcecosse]

Query from another A series forum - can anyone confirm the crank pulley bolt thread for me? I have in mind that it is 5/8" UNF ??

[Artful Dodger]

no idea on the question, but your signature is awsome!!! made me laugh:P

[Pigeonto]

Query from another A series forum - can anyone confirm the crank pulley bolt thread for me? I have in mind that it is 5/8" UNF ??

Dont know if I'm missing the joke or whatever after the fiasco a few years back,but will answer factually!! Its not UNF which I think is 18 TPI. Its 5/8" x 16 TPI Whitworth Form(WF) and I have the tap to prove it.*********** EDIT ah ha ,well done Dilligaf, thats 2 of us

Edited by Pigeonto, 23 February 2012 - 05:40 PM.

[bmcecosse]

Ohhh - right thanks for that - is it definitely Whitworth then -and not UNC ???

[bmcecosse]

Ok - thanks!

[Pigeonto]

Dont put a 5/8 whit or unc up it, they're 11 tpi

[dklawson]

Yes, I remember that old thread. It was definitely confirmed (as Dilligaf said) that the thread is 5/8-16 Whitworth Form and it is listed as such in the factory manuals.

There IS a 5/8-16 UNS tap (special) tap. However, it is a 60 degree thread profile and will shave some material out of the crank when used to chase the threads.

I modeled and superimposed the two thread profiles (5/8-16 WF female and 5/8-16 UNS male) during the old message thread. The interference between the two is minimal which is why people probably got away with chasing crank threads with the UNS tap. However, if you have access to the correct WF tap, use it. At one time GuessWorks had some of those taps made. If you need one, you might want to send him a PM.

[Dan]

Maybe you lot know because of that post, but it's in the manual ffs.............

Given how many Mini and A series specialists believe it's a UNS thread, and sell taps, tooling, screws and bolts to that form, it's an understandable mistake. Not all manuals agree with the factory manuals either, and not everyone has a factory manual.