Alternator shaft rethreading

mmasse · mmasse's Garage

I damaged the thread of my alternator shaft. Anyone knows where can I get a M16 x 1 die?? Or, is it ok to rethread it to a more standard size?

thanks

Formerly Steve Wilkinson · 05-20-2005, 04:21 PM

My alternator shaft was boogered up and the local redneck alternator shop that rebuilt it quite competently also rethreaded the shaft and put on some standard inch-fraction U.S. nut. The whole thing probably would have sent Stuttgart into heart palpitations, but it has done just fine for two years now, most of which has been high-rpm track time.

Stephan

350HP930 · 05-20-2005, 04:46 PM

If you can't find the right die a thread file may also be able to properly unbooger your shaft.

zachsbug · 05-21-2005, 03:01 AM

I have just recently had a go a round with the shaft & nut. I was able to clean the shaft up with a slick took that one of the maintenance guys at work had. The shaft was not boogered up to bad but the nut on the other hand was. Looked high & low in my area for a 16x1 nut but not find one. I ordered one from our host along with some other stuff, had to wait 2 weeks to get the nut but thats what I needed.

Wil Ferch · 06:27 PM

MMase....careful....there was a change from 16mm x 1mm pitch..... to 17mm x 1.5 pitch, at some point. I think around '83. What year is your car ??

Wil

zachsbug · 05-22-2005, 05:55 AM

I have a 68 T.

Wil Ferch · 05-22-2005, 06:51 PM

Should be 16mm, then.....

Wil

H.G.P. · 05-22-2005, 07:32 PM

If it's the Marchal nut, you might try to use this board "search" feature above.

Rufblackbird · 05-22-2005, 07:42 PM

Quote:

Originally posted by 350HP930
If you can't find the right die a thread file may also be able to properly unbooger your shaft.

exactly what I bought (from the Snap on guy) and used to unbooger the shaft on my '76 when I couldn't find a M16x1 die anywhere.

mmasse · mmasse's Garage

Well, after trying to find a 16x1 during the whole weekend. I gave up I will by a 5/8 die and rethread it.

Cool anyone help with GOOD source for tools on the net, I recently arrive to the US.

thanks

350HP930 · 05-23-2005, 02:31 PM

Try a thread file first.

rusnak · 04-23-2007, 02:22 PM

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.

Formerly Steve Wilkinson · 04-23-2007, 02:36 PM

Porsche people hyperventilate when alternators are mentioned. The number of washers between--or outboard of--the pulley halves seems to be the only thing staving off global warming, and thread and nut sizes seem to have been handed down on tablets from Moses Porsche hisself.

All I know is that four years ago, I took my '83SC alternator to a redneck alternator shop here in Upstate New York--hey, they do racecars, like the Saturday-night-special Camaro supermodified dirt-tracker they run at the Orange County Fairgrounds, also garbage trucks, farm tractors and bulldozers...--and they gave it back fully rebuilt, chargin' just fine, and the guy said, "We re-threaded your shaft, it was all boogered, and there's a 'Murrican three-quarters nut on 'er now, hope yer Porsh doesn't mind."

It has been running fine, lots of track time, ever since.

Take the thing to a good local alternator shop that probably considers a 911SC to be a pedalcar and tell them the problem. Unless you want to concours the car, that is...

304065 · 04-23-2007, 02:47 PM

Can I offer an alternative viewpoint?

Get a new alternator and don't screw around with re-threading the shaft. When you cut new threads you cut across the grain structure of the metal and if the finish isn't as good as original you create more stress raisers. Now you take this out on the racetrack and spin the crank at 7,000 RPM, so the fan is spinning at nearly 12,000 rpm, and you're supposed to be confident that the vibration isn't going to hurt anything? If the shaft breaks it's going to be a problem.

Stephen, LOL, the number of washers DOES mean the difference between wearing out the fixed half of the pulley on the fan, the alternator bearings and the #8 main. I hadn't heard that it had anything to do with carbon emissions, but to tell you the truth I have been staying out of the OT forum lately.

I also spent a few minutes today seriously pondering the merits of REAL cadmium plating vs. clear zinc if that gives you any idea where my head's at. . .

Formerly Steve Wilkinson · 04-23-2007, 02:50 PM

Where'd the Citabria go? That'd fix yer head.

304065 · 04-23-2007, 03:24 PM

The Citabria went to a very nice man in Superior, WI, who lives five minutes from a hangar he rents for it for $90/mo. Breaks my heart every time it's CAVU here.

rusnak · 04-23-2007, 03:48 PM

wtf....I'm pretty sure that if my friend took his SC to 14,000 rpm the alternator would be the least of his problems.

It's not my car, so I'm not going to take it to the redneck alternator shop (I can't believe someone actually gave this advice as a starting point). Why don't I run to the redneck garage for a valve adjust too? Heck why don't I git the engine torn 'part an' put back 'gether raght fo' sho?

Formerly Steve Wilkinson · 04-23-2007, 04:15 PM

We're talking about alternators here, not 917K engines. But take it to the boutique if you wish. Certainly many people do.

rusnak · 04-23-2007, 04:39 PM

Look Steve,

No offense. You can take your alternator wherever you wish.

I posted this question so that I could help my friend and his dilapidated 911SC. "take the (fill in the blank) to the redneck shop" goes against the whole spirit and intent of this board. Don't you agree? I'm trying to fix my friend's car, not tell him to go to this or that shop. That is a lazy and aloof response. You might as well have a ciggy dangling from your lip with a Bud in one hand and and waving an imaginary person away with the back of the other.

I think the root of the problem is that he took his car to a redneck shop to begin with. Personally, I don't subject my Ford F150 to such abuse as that, but that's just me. I like my car to be reliable.

Formerly Steve Wilkinson · 04-23-2007, 05:09 PM

What I'm trying to say is that the "rednecks" know far more about alternators than any of us do. An alternator is not a "Porsche part" that requires super-skill. It's a generic machine. I have found that shops that specialize even though they can't spell Porsh are often vastly better than the shop-coated Dieters. When I wanted my 911 engine balanced, I took it to a place on a back street in Newburgh, New York that builds hundreds of super-modified and sprint-car small-blocks every month--big sport up here.

I think we sometimes forget that our antique engines are well within the capabilities--at least in certain areas, like alternators--of goo old-fashioned mechanics (not "technicians" or "service specialists") to handle.

Perhaps my suggestion that your friend take his alternator to a good local shop that has been in business for 50 years indeed does go against "the spirit and intent of this board." Ask me if I care.

Lazy and aloof? I was entirely serious. I think it's lazy and aloof to characterize the craftspeople who work at these places as having a ciggy dangling from their lips and a Bud in their hand.