Norton rocker spindle cover bolts

I am planning on installing stainless rocker spindle cover bolts.

The original bolt is 1/4 Whitworth, which is pretty similar to 1/4 NC:
Both 20 TPI, Whitworth 55 degrees vs UNC Whitworth 60 degrees, Whitworth radiused crest and valley vs UNC no radius.
A 1/4 NC bolt screws nicely in the head.

I can't decide if I should chase "speciality" stainless spindle cover bolts, which may or may not be 1/4 Whitworth.
OR
Go down to my local fastener supplier and get 1/4 NC bolts in a head shape of my choice.

Are 1/4 NC bolts in a 1/4 Whitworth hole a bodge? What have others done?

Thanks,
Stephen Hill

I have used SAE, run a tap thru, hardly nothing comes out. They are covers, If they were crank bolts, no way.

For the time and effort, just as easy to buy 1/4 Whit stainless ones surely!

I used 1/4x20 SAE stainless socket-head screws, no problem.

It's been years but I bought a set of the correct thread form in stainless from one of the usual suppliers for reasonable money. Someone must have them in their catalog.

It would be interesting to know if in theory they are Whitworth or UNC thread forms ?
Both are 1/4" x 20 tpi, but as mentioned already UNC has a slightly different thread form to genuine Whitworth thread form.

A set of UNC socket screws fit right up, but feel a little loose.
A set of whitworth also go in quite well, and don't feel much different.

BTW, Nortons used these same fasteners in alloy Dommie and Atlas heads, going back into the 1950s.
But did they actually convert from Whit to UNC for the Commando, or keep using the same ???

And, we assume the above references to SAE are really talking about the UNC version of SAE.
Or that is some bodgery going on....

Rohan said:

It would be interesting to know if in theory they are Whitworth or UNC thread forms ?

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There is no evidence to show that any of the head fastener threads were changed to Unified.

Rohan said:

BTW, Nortons used these same fasteners in alloy Dommie and Atlas heads, going back into the 1950s.
But did they actually convert from Whit to UNC for the Commando, or keep using the same ???

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Although there was a change of part number when the cover plate 'bolts' were increased in length (as a result of copper washers being fitted from eng. 203884) according to AN, they were 1/4" BSW until the end of production.

http://www.nortonmotors.de/ANIL/Norton% ... 03&Part=31

NORTON 850 MK III - 1975

Item: ROCKER END PLATE SCREW 1/4"BSW
Part Number: 063124

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The rocker covers are actually held on with a stud and a nut. I know you guys all know this but it sounds like you are considering the use of a bolt instead of a stud and nut. My problem with that is that a bolt goes in and out of the actual aluminum threads in the head. No big deal right? You are never really going to wear out the threads in the head right? Well, I like a stud and nut set up because the stud is replaceable and the threads in the aluminum are preserved.
I lock tight the studs in with red high strength lock-tite. Then use blue light duty thread locker for the nuts. The best thing I have ever done for my rocker covers is use the orange true silicone gaskets. These are made by an aviation parts manufacturer who makes gaskets for Lycoming and Continental engines. Totally reusable and a bit stiffer than the black rubber ones I have tried.

motorson said:

The rocker covers are actually held on with a stud and a nut. I know you guys all know this but it sounds like you are considering the use of a bolt instead of a stud and nut.

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The discussion is about rocker spindle cover bolts, not "rocker cover".

L.A.B. said:

motorson said:

The rocker covers are actually held on with a stud and a nut. I know you guys all know this but it sounds like you are considering the use of a bolt instead of a stud and nut.

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The discussion is about rocker spindle cover bolts, not "rocker cover".

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(Hopefully somebody needed to hear my little lecture. )

I have always used 1/4 20 stainless buttonhead screws with no problem what so ever.

Button head allens on the coil mount bolts save time and aggravation. 1/4 28 I believe

motorson said:

The rocker covers are actually held on with a stud and a nut. I know you guys all know this but it sounds like you are considering the use of a bolt instead of a stud and nut. My problem with that is that a bolt goes in and out of the actual aluminum threads in the head. No big deal right? You are never really going to wear out the threads in the head right? Well, I like a stud and nut set up because the stud is replaceable and the threads in the aluminum are preserved.
I lock tight the studs in with red high strength lock-tite. Then use blue light duty thread locker for the nuts. The best thing I have ever done for my rocker covers is use the orange true silicone gaskets. These are made by an aviation parts manufacturer who makes gaskets for Lycoming and Continental engines. Totally reusable and a bit stiffer than the black rubber ones I have tried.

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I unscrewed the studs and used 1/4x20 stainless allens on those, too. Again, no problemo.

Whilst nothing really to do with lightly stessed rocker cover screws / bolts.........
Quote. Given in the book 'Engineer to Win' (Carroll Smith) and taken from the book 'Prevention of Failure in Metals' (John Wiley and Sons. 1941).
'Any thread is a stress raiser, smoothly radiused threads are better than sharp threads. But might is right and the Whitworth thread form is extinct'.
Bet those Yanks were to blame for UN threads......and the French for bloody metric!!

IF using std Norton rocker covers remember that the tooling shoving the ears out to lock the rocker shaft in position was towards the end TOTALLY knackered and the ears fail to do their job resulting in rocker spindles rotating in heads and at least one friend making the odd bob or two on a regular basis repairing the oversize holes in heads. Personally I made one piece stainless covers 40 odd years ago by having the Marconi Radar tool room machine a length of 1/4 inch thick stainless leaving a lump in the middle which they then gave to me to chomp up and shape. Never understood why no one made them in stainless for sale to the public using the lost wax process or some other process.
As for using 'stainless' ...
!. Please remember that dissimilar metals cause corrosion, especially stainless into aluminium alloy. For the navel radar gear I worked on for a few decades all bolts were dunked into a yellow gunge called Duralac before fitting to stop the problem.Bloody stuff got everywhere!! In my youth I fitted stainless barrel studs into a set of Dommy crank cases...There was not much aluminium thread left when I finally managed to remove them a few years later...and thus i learnt about the benefits of cadmium plating and passivation......
2. Norton wheel spindles were made from steel with a tensile strength of 55-65 tons per sq inch with an Izod of 40. Many decades ago I found only one stainless steel that matched these values (17-4 PH in condition 1075) and decades ago when I tried to obtain some for wheel spindles was told I could have some IF I ORDERED ENOUGH from the mill.Nothing in my British Standard book matched these values. So what do people flogging stainless wheel spindles use? I assume they also supply with them torque figures to employ when tightening the new stainless rear wheel spindle or am I dreaming again in assuming people know about such things.... A few years back one friend riding his Commando coast to coast in the USA had a rear wheel stainless spindle fail. Did not Jimmy Githrie die at a pre WW2 German GP when a rear wheel spindle failed?? I seem to remember my late Father telling me the tale as we stood looking at the Les Graham Memorial above Ramsey one evening in the mid 1950s during TT week...

I originally asked if subbing 1/4 NC for 1/4 Whitworth was a bodge.
Sounds like lots of folks do this, especially in a relatively low stress application.
I ran a 1/4 NC bolt in the head: fit perfectly.
I also discovered that if you order rocker spindle cover spindle bolts from suppliers, some places sell you Whitworth, some sell you 1/4 NC. And some tell you at the front end what you are getting, some don't. That is how substitutable the threads are.
Conclusion: not a bodge.

Leadbeater makes a good point about aluminum and stainless leading to (galvanic) corrosion. Anybody who has played with an outboard or sterndrive knows what can happen, particularly in a salt environment. Spindle rocker cover bolts soak in engine oil, so IMHO this is a non issue. If you are concerned about aluminum and stainless creating corrosion in motorcycle installations, you can electrically isolate the two materials: non-acetic silicone caulk, grease, or neverseize. One of the best products is good old lanolin grease -hard core mariners swear by the stuff.

Stephen Hill

Lately I have been having a persistant oil leak through the spindle cover bolts. I am going to try some yellow teflon tape on them tonight. I have become a great fan of the stuff lately.

seattle##gs said:

Lately I have been having a persistant oil leak through the spindle cover bolts. I am going to try some yellow teflon tape on them tonight. I have become a great fan of the stuff lately.

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Isn't that what the gasket and copper washers at supposed to contain?

seattle##gs said:

Lately I have been having a persistant oil leak through the spindle cover bolts. I am going to try some yellow teflon tape on them tonight. I have become a great fan of the stuff lately.

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Had the same issue with the leaking. New gaskets, new copper washers, Teflon tape, Teflon goo, permatex, the list goes on. Nothing worked until I tried Hylomar. Tough finding on the shelf but easy to order. Pep Boys in Everett, WA. did stock it. A friend of mine is a 75 year old retired MG, Triumph, Porsche mechanic and told me about it. I was told that it was developed by Rolls Royce. I haven't found anything that works better.

yellow teflon tape is just another option but it works well even on petcocks.

For general knowledge...there are two types of teflon tape...the white stuff is for general plumbing and the yellow is for fuel and other petroleum products.

Not so general knowledge: white teflon and yellow teflon are made of the same material; the only real difference is thickness, yellow being thicker.

Stephen Hill