Crankshaft thread size

[Mike Farmer]

 

Hi..
A65T Bitsa. I am at the stage of fitting alternator to my 64ish A65 and the nuts won't run. I have an old nut and a new one so I suspect the thread. I know this is not the ideal time to find this problem and I should have etc. However this is where I am.

So help please. Before I grab the die set and start the job, what is the thread size and type?? I can only find one size nut listed and it doesn't give the relevant info. So I guess/hope the thread was never changed.

Mike

[JulianS]

5/8 x 20 tpi cycle thread.

[Mike Farmer]

 

Thank you

Mike

[Nanonevol]

I and others have had this same problem.  I believe it is poor quality aftermarket nuts.
I bought one from a vendor and one from an Ebay seller and neither would thread on though appeared to be correct size and thread.
I think what I did was drill (or file or grind) the "lead in" part of the nut as it turned out this is where the problem is.

I was lucky enough to have a junk crank to force the nut on and "break it in".

[Mike Farmer]

 

Yes I can understand that, however I also have a used nut that wont run so I'll run the die along it to make sure. Then probably retap the nut.

Mike

[idie]

I think the problem is a worn tap. They keep on using them and as they wear the tap cuts an undersized thread.

[Nanonevol]

Oh, right you said you had a tap.
I resorted to more brutal methods.

[chaz]

probably not a worn tap, we dont use many taps anymore mainly thread hobbing with a fixed pitch tool that can be used for diameters with the same pitch or throw away tip tools that also are pitched and can be used for different diameters.
As most of these tools are not available as BSC, modern nuts are produced with tips with the correct tpi but not necessarily the correct thread angle.
Any taps made now are made in China , not necessarilyy to the standards BSI demand.

[idie]

That's interesting.

[chaz]

just finished a nightshift, later today I will post a few pictures and explanations