Hi the threads on the shaft for my alternator pulley are worn/stripped so I cant tighten my belt. Does this mean a new alternator? 
You could try to re cut the threads but it might end up being a replacement.
Thanks; it’s a total bummer as it was less than 24 hours since I had it running for the first time in 9 months 
Its a strange one the threads stripping tho? Was the nut loose ?
No not loose,well it’s got threads at the end but not where you’d want them, the belt was super tight and freyed. the threads are sort of flat on one side, no idea when in its past that happened.
Are you sure it’s not the nut that’s stripped, a picture would be helpfull
Have you got plenty of the shims? Etc or are the threads properly stripped?
Thanks, I wish it was the nut; it has about a bolts depth of good thread at the end then the bolt just skips and rattles where the threads are duff.
Thanks, there’s not loads 5 or 6.
It’s possible, if not shimmed out far enough the belt will be far too loose. I’m just trying to figure out if the threads are stripped or it’s fully tight.
Another thought is the belt the correct size? I’ve got aftermarket pulley on mine and it’s not easy getting a belt to fit correctly as there’s a few sizes and different makes can be slightly different.
Is it a standard engine? Standard pulleys?
If its slightly damaged you should be able to run a dye down the thread, should be M12 x 1.5 or maybe the nuts also got damage?
hi threads are a bit stripped as if you try tightening the nut to that section it almost thightens then pings back; if you take the pulley off and do the bolt on its on then there is a section where the bolt just rattles on the shaft.
@mark I doubt any of its std, and my instinct is that the belt is maybe a wee bit too long (900mm). I think the bolts fine but I’m not mechanical at all. Thanks
If your saying the belt is tight then adding shims in-between the pulleys will loosen belt and also move nut further out on the shaft
@Jigs, no the belts not tight, it had one shim in the pulley. @mark suggestion of rethreading might work - again I don’t know enough to judge. Thanks again everyone
If belt is loose the shims just under the nut will tighten belt and pull nut outwards and hopefully catch a good thread.
And maybe a new belt would help too if its old a stretched/worn
thanks; I’m kinnda worried now about touching it and making it worse; @Jigs are there any mechanical minded members near me that might be up for popping past sometime; I’m off Drumbrae North
@Texas ill be in Sighthill this morning I don’t think that’s that far from you ?
Happy to pop in have a wee look