C2 Alternator Rotor Shaft thread size?

[Donald H.]

This is a 10DN Delco Remy alternator for my 66. It is part number 1100693. The threads on the end of the rotor where the pulley mounts are slightly stripped. Enough so that I can not get the pulley retainer nut onto the shaft. I've tried to use a very small file to clean up the threads, but this hasn't helped much.

I want to buy a thread die to clean up the threads, but so far I have not been able to clearly identify the size.

From searching the web, the rotor shaft is identified as being 17MM. The nut is identified as .668-20 x 15/16 F x 5/16 T. I found one reference that equated the .668-20 to 11/16 - 20. But this is a little confusing as:

17MM should equal .669 inches, or within .001 of the .668
11/16 in decimal is .6875, which seems a bit to large.

I can find a reasonably priced ($15) 11/16 - 20 die on Ebay, but I'm not sure if that will work or completely mess up the threads.

Anyone know for sure know the size of the rotor shaft pulley end threads?

Thanks,

Don

[David H.]

Re: C2 Alternator Rotor Shaft thread size?

Donald,

If this is a reconditioned/restored unit I would measure the threads rather than depend on a published value. You can never be sure of what the rebuilder actually did.

A couple of thread guages, one standard. and one metric are needed. In your post you mentioned "thread die" - for this application you need a "thread chaser" kit - as you just want to clean up the threads rather than cut new ones. Kits and thread guages are available at a many locations, mine is from Sears and works ok for a hobbyist. A kit should have a selection of metric, standard course, and standard fine taps (for chasing nuts) and nuts (for chasing shafts) in various sizes - some kits will also have thread files (although I've never had much use for them)

Using the thread guages identify the number of threads per inch/mm, then choose the proper nut chaser to clean up the threads.

[Joe L.]

Re: C2 Alternator Rotor Shaft thread size?

This is a 10DN Delco Remy alternator for my 66. It is part number 1100693. The threads on the end of the rotor where the pulley mounts are slightly stripped. Enough so that I can not get the pulley retainer nut onto the shaft. I've tried to use a very small file to clean up the threads, but this hasn't helped much.

I want to buy a thread die to clean up the threads, but so far I have not been able to clearly identify the size.

From searching the web, the rotor shaft is identified as being 17MM. The nut is identified as .668-20 x 15/16 F x 5/16 T. I found one reference that equated the .668-20 to 11/16 - 20. But this is a little confusing as:

17MM should equal .669 inches, or within .001 of the .668
11/16 in decimal is .6875, which seems a bit to large.

I can find a reasonably priced ($15) 11/16 - 20 die on Ebay, but I'm not sure if that will work or completely mess up the threads.

Anyone know for sure know the size of the rotor shaft pulley end threads?

Thanks,

Don

Don-----


The nut used for all original DN series alternators was 5/8-20 thread size. This is an oddball but I think thread chasing dies are available.