Super Rocket 1958 clutch mainshaft thread

[Roadrocket649]

Hi Guys

Could anyone advise the thread & size on the clutch mainshaft

I am trying to have a new nut turned but all the standard bolt sizes tried, do not match

I thought it would be a BSW?

Appreciate any help

[bsa-bill]

BSCY - cycle thread I would have thought of the 20 tpi size

[Goldy]

As bsa-bill says 20tpi BS Cycle 5/8" diameter. The nuts are available form any of the BSA parts suppliers such as, Supreme Motorcycles, Draganfly, C & D Autos.   All the best.

[Roadrocket649]

Hi Goldie

Thanks for your assistance

Had received a nut from Draganfly, but t would not screw up the shaft

The bike appears to have a Cush Drive Clutch, which the Draganfly catalogue shows the nut to be a 42-3171
However, they changed this to a 42-3267 nut which shows on their catalogue for a Non Cush Drive clutch

The nut dimensions and the associated washer centre hole dimensions, and the lockwasher are also different

It could also be an over- plating problem on the threads

[Roadrocket649]

Many Thanks BSA-Bill

I have advised my friend who was going to make one, because as mentioned to Goldie, for some reason, the Draganfly nut would not run up the mainshaft

I hope he can programme the machine to do this

Once again, many thanks for your swift response

[Colsbeeza]

I also just received a 5/8" 20TPI Clutch Nut from Draganfly. It also will not take to the mainshaft thread although it looks identical to the thread of the old nut. I will get hold of a tap to see if the thread will clean-up. I can buy a tap for A$47, so will try to borrow one. The washer which also came with it will not fit over the small diameter of the nut, but I can worry that out to fit OK. They might be very old stock.
My gearbox and clutch seem to be one problem after another. Happy Days.!! At least the end is in sight.
Col

[Colsbeeza]

Chaps,
I was not able to locate a 5/8" 20TPI Tap, so purchased one from LPR Tools in Victoria Australia at great expense. It turned out to be 5/8" 20TPI UN thread, not CEI. After a bit of research, I decided to use it. It is part of the Unified National system (Series with Constant Pitches), and is also a 60 deg thread form. Seems to be quite a range of diameters. Unlike CEI, which has a rounded edge on the threads, UN has the edges flattened off so I did not expect it would remove any more steel than a CEI tap would do.
I also purchased a 5/8" 20TPI UN button die to check if it would run down the mainshaft thread. It did - by hand without using a die holder.
The tap did the job, and the nut ran down the thread with a little more force than finger-tight.
Not sure if UN threads are very well known on the Forum, so thought I would write down my experience.
May be a useful source for larger CEI threads if unavailable. I have attached a useful table I found on the Net.
The large washer machined out to fit OK.
Cheers
Colin

[berger]

I have recently bought two mainshaft nuts one for a 6 spring clutch and a nut for a 4 spring , neither of which will fit any of 3 shafts I have tried, the 4 spring nut I started with goes on about 3 threads and the 6 spring nut about the same, I will not force them on they are too tight, I will be looking for a tap and die to try and see what's going on. I also bought a mainshaft key which is  small . I think the problem with these parts is the makers don't care and neither do the sellers, they are also at the sort of price that it isn't worth sending them back

[beezermacc]

I suspect these are from MCA. I've had the same problem with all my recent stock so, before sending them out to customers, I've been running them up and down an old mainshaft held in the vice. I have now invested in a tap to make the job easier.

[berger]

correct beezermacc looking at a packet now with union jack sticker on , are they made in uk ? if so the plots been lost I will take them to my local engineering shop for remedy instead of buying a tap I will possibly never use again.

[berger]

well it seems MCA [ aston- birmingUMM ] who have been around some years now, I would have expected better because these nuts I have are very tight. never mind it will be sorted, but not today --- its pub time yeah

[duTch]

 

...I was not able to locate a 5/8" 20TPI Tap, so purchased one from LPR Tools in Victoria Australia at great expense. It turned out to be 5/8" 20TPI UN thread, not CEI. After a bit of research, I decided to use it. It is part of the Unified National system (Series with Constant Pitches), and is also a 60 deg thread form. ..............

 Without wanting to go off track, I was curious about this as I have some 'NF' taps that I kind of inherited and have always assumed them to be UNF and apparently are, so wondered if the UN threads were same but apparently not- just part of the same (little known) system- little known as there's not much information on the interwebbs..... the searches I did for 'Unified National system' mostly return results for Health, Education, or Judicial systems , except for the Wikipedia item "Unified Thread Standard", related to UNF/UNC which only gives a brief reference to 'UN' 

 The download took a couple of attempts but the mud is a bit clearer now- not.....

[chaterlea25]

Hi All
Dutch,
All you could ever want or need to know about threads can be found here

https://www.gewinde-normen.de/en/index.html

John

[duTch]

 

.....All you could ever want or need to know about threads can be found here....

 Thanks- I think  I bookmarked it for a rainy day

[ironhead]

I think you'll find these are 5/8" x 20  UN  different series than the standard UNF / NF