I've attempted to fit a new 12v, 3 phase alternator to my basket case rebuild of a '62/3 Norton 650SS.
It all fits OK, that's not the problem. It's the 1/4" x 26tpi studs and nuts that retain the stator that are the problem. Both the Haynes Manual and the Clubs Dominator Service Notes say that the nuts should be tightened to 15 lbs/ft of torque. My problem is that they strip long before that torque figure is reached. They were new studs and nuts, from a reputable Norton parts supplier. I wondered about the calibration of my "Britool" torque wrench but I checked it by clamping the 3/8" square in a vice and using my digital fishing scales. Set to 15 lbs/ft, it took a pull of 12lbs 10ozs at a radius of 14.5 inches to make it 'click'. That equates to 15.25 lbs/ft, so it wasn't my torque wrench at fault.
Any comments or advice would be appreciated.
John
I'm surprised to hear that…
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Having never.....
Having never torqued such nuts, but I do think they should take 15. An academic question is the stud or nut or both stripped? If the nut is still good then I wonder if the stud is the 'softy'? For my excuse re Dommie Service notes, this figure would have been proffered by those with greater knowledge than me, I think it reasonable, but have never tried it. The next time I try these studs I might just see what they are done up to?
But of course this does not help your present quandary.
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Like others I'd never…
Like others I'd never consider using torque wrench on such small fasteners, except for high tensile big ends. Even so, a Google search suggests from 5 to 8 lb.ft.
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About 5ft lbs for 1/4 bsc
Hello John,
If you dig up standard imperial fastener torque charts from Internet you will find various maximum fastening torques, being much higher for the highest tensile steels.
In your application, with probably normal fastener steel, 5 ft lbs would be a sensible maximum for 1/4 ins. Try it, then undo and refasten without torque wrench. It will give you a "feel" which can be carried over to all your many 1/4 inch fasteners.
I will probably be shot down, but 15 ft lbs on 1/4 ins is plain wrong for a steel nut.
A 5/16 ins nut might just survive 15 ft lbs, but this is usually a head fastener with extended length nut.
Most of us get by with "feel" which we developed by trial and the occasional stripped thread.
If in doubt the modern thread lock adhesives give peace of mind. My stator nuts have split lock washers under (as specified) .
Peter
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I relied on good old…
I relied on good old fashioned feel on my Commando stator fixings with a dose of Loctite thread locker as back up similar procedure for most if not all of my metal nuts!
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From The Horses Mouth
This is one part of a Norton where decent quality studs and a fairly high torquing is necessary to overcome the issue of engine vibration. The attached Andover Norton sheet shows their recommended torque settings for the stator stud nuts.
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Yep... I've seen that quoted…
Yep... I've seen that quoted in 3 different places, now... but have they actually tried to torque those little nuts up to 15 lbs/ft or are they just copying from each other? What's the point in specifying that figure if the nuts/studs strip.
I've ordered three new studs from Andover Norton but I won't be trying that torque again, I'll trust to my 'feel'.
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Just had a look in my …
Just had a look in my "oddments" box ( we all have them!!) and found a few 1/4" BSF Philidas self locking nuts. Seem to remember that they were used on my Meriden Triumph alternators. Any reason why I shouldn't use them on the Norton?
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I would be more concerned…
I would be more concerned about the thread into the Alloy basket..Certainly the only time i strip threads is when using a torque wrench !. Those 1/4 studs into the alloy slider is another area of concern.
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I'm surprised to hear that people use a torque wrench on those nuts.
I know that's not much help!