I seem to remember seeing an article here about the vagueries of the 2 crank nuts -
some say 5/8" x 20 tpi which is Cycle / CEI
but brand new CYCLE nuts just do not even look at starting on my undamaged threads.
there are options for these nuts , a thinner one for the timing side and a stepped one for the drive side.
but i have about 4 C15 parts books that cover a good assortment of the model and there are loads of differing part numbers and even differing mainshafts.
my ZEUS book gives me an option of UNF for 5/8 x 20 , has anyone else had this thread on their bikes?
A number of CEI threads sizes come in 2 pitches, for example 1/2" and 5/8" both come in 26 tpi or 20 tpi.
You need 5/8 x 20 TPI CEI. As CEI is 60 deg and so is UNF a 5/8 x 20 UNF nut will fit but it may be tight.
You can get 5/8 x 20 CEI nuts.
ironically, my Bantam D7 rear wheel spindle nuts are 5/8 x 20 cycle and these rear wheel nuts screw on nicely to my C15 crankshaft .
I have just bought a 5/8 x 20 cycle die and will run that down the crank and see if that helps
If the wheel nuts run down nicely then the thread isn't at fault, so why would you decide to run a die down it? Better to get the correct nuts or even run a tap down the ones you have?
Crankshafts are too expensive to mess up.
Is the nut 40-0454 (5/8 x 20 CEI)? In which case these are available for around £8. Thread is the same as the Bantam wheel nut 90-6222 but the wheel nut is a (thin) half nut.
Confusingly the parts also list 29-2023 which is the same as the front wheel spindle nut but sellers are listing this as 5/8 x 20 UNF.
If the Bantam nut fits then its looking like CEI.
Thank you both for your thoughts, the part numbers you quote are the ones I'm looking at. I'll try and find a tap rather than a die maybe.
I seem to remember that the UNF threads are triangular and not rounded, or vice-versa. So they will fit onto a British thread but it could be a bit of a squeeze, as the thread tips mould into the new shape.
Hi,
If the crank threads are good I would be inclined to adapt a nut but I am sure that someone out there has the correct thread.
Try C&D Autos 01564 795000.
Dave.
Draganfly are listing 40-0454 as 5/8 x 20 CEI which is a good sign as some others don't give the thread.
I thought I pointed this out a while ago.
There are two cycle thread standards.
It seems that BSA's subcontractors didn't stick to the same standard.
Even within those standards sizes drifted.
Do it right and avoid parts shops for problem parts.
https://pesltd.uk/?product=29-2023 (https://pesltd.uk/?product=29-2053)
https://pesltd.uk/?product=29-2053 (https://pesltd.uk/?product=29-2053)
https://pesltd.uk/?product=42-5864 (https://pesltd.uk/?product=42-5864)
Mark
Mark, I have amended your link so they work.
Rob
Forum Admin
thank you,
these links didn't work , but i got onto their website and ordered a pair - fingers crossed
Sorry it seems we have lost the plot on these too.
It seems there is some mistakes on our website.
From our manufacturing notes, 37-1798 should be the slim 9/16 BS Hex 5/8" x 20 large cycle.
Also 29-2023
I think you may have been sent the wrong ones Rhyatt, but it will be sorted quickly.
Mark
Thanks Rob.
Out of curiosity I spent a bit of time looking at the part numbers and the list of fasteners I got off the web. It has got in a bit of a muddle with both 5/8 and 9/16 listed and CEI, BSF and UNF. CEI and UNF are 20 TPI (of course CEI can be 26 TPI) and UNF is 20 TPI. 5/8 BSF is 14 TPI
Its not a single source that's wrong, somewhere confusion has got in and the error picked up and repeated.
Standard thread tables just confuse things Rob.
BSF always has 55-degree thread. The pitch can vary.
Cycle thread is almost unified in form to a point where 5/8"x 20tpi UNF can easily mixed with 5/8" x 20 tpi cycle.
If my memory is correct there is a 1920's and a 1950's standard.
A late nut often won't fit an early bolt.
That said, the 1920's tolerances are vague.
On top of this a manufacture can choose to put any pitch and form on a fastener they like.
With UNF, there is UNF Fine and also UNF extra fine.
Oh, what fun.
Then you have electroplaters that leave parts in the tank too long and nothing fits.
Mark
Oh dear , have I unearthed a can of worms !!!
I've got a pair of PES nuts coming , see if they glide onto the crank without a care in the world !!!
If people have issues, it's good to mention.
That way with hope it can be resolved.
Mark