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I'm resurrecting this thread hopefully to get some advice/ ideas.
I've been helping one of my friends who has a rather forlorn 911SC that has had a lot of alternator problems recently, but thankfully it now works and charges 14v. We've changed the alternator bushings and found a bad wire in the charging system. The one remaining problem is that the alternator threads for the fan pulley/ nut are badly flattened in spots.
It looks like the alternator shaft is 16mm (measured w calipers) and the thread pitch is unreconizable. The thread gauge says 1.2 but I'd swear it was 1.0 or so. Several of the threads are quite flattened. I was looking at two other nuts that were destroyed from being tightened on the alternator shaft. They are 1.2 pitch, so I don't think that's what the correct thread pitch is. I read that the Marchall alternator used a 16M x 1.0 thread, so I'm sort of thinking that's what this is. It's an 1982 911 but the alternator is not stock.
I'm thinking my way through how to help fix this alternator, and in addition to not being able to find a 16mm x 1.0 nut, I'm thinking the original nut wouldn't have enough metal to grab onto if the threads are re-cut using either a thread repair file or a dye, if I even could find a 1.0 thread pitch dye.
Is it possible to re-thread the alternator with a 5/8 in dye? The 5/8 is approximately .2 mm smaller than 16.0 mm. There should be enough material to make good threads, even though the thread pitch is different (i.e. the dye would be "cross threaded"). Or is it better to go for a 15mm dye? Part of this problem is that no one sells 15mm nuts. They all go from 16mm to 14mm. I don't think it's wise to remove too much material from the shaft. I plan to hold the alternator steady by having my friend hold the fan still. The shaft is keyed for an allen wrench, but I'd need to use a wrench instead of the dye handle to turn the dye.
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