Centre stand pivot bolt

[paintingsteve123]

Morning guys,
On my 1953 plunger the main stand is held on with pivot bolts my question is what is the thread.
It appears to be 20tpi and roughly 0.370 wide
But looking on charts I can't seem to find that size.
The nuts I have for it are just regular ones but I think they should be the castle ones as their is a small hole for a split pin.
Also any idea where I can get those nuts
Thanks in advance.

[groily]

Slightly worn 3/8th (.375") BSF I would think?
(In BSC (Cycle) it's not normal to see 20tpi pitch at less than 7/16ths diameter. It's certainly not BSW metric or UNC/F.)
Borrow a known nut from elsewhere off the beast and see how it fits?

[paintingsteve123]

Thanks for the info, and you are right b s f.
And with that info I have found them online .
Although not cheap , £6. 24 for 2.
Thanks again. 👍

[groily]

Expensive or what! But maybe not silly for castellated, which might be intended for big ends or summat, and made of good stuff  . . . ??
The main thing is you know what you need.
It might be worth getting a few of the commonly-used taps and dies for other bits and bobs? Very handy for cleaning up threads, and for making them too if a bit of suitable stock is available.
These are probably the best people if you wanted to get some in: https://www.tracytools.com/product-category/taps-and-dies/

PS Cheapest I could see: https://morrisregisterspares.co.uk/product/castle-nut-3-8-bsf/ at £1.66 each, but + P&P, maybe VAT, etc - not freebies.

[limeyrob]

Plain BSF nuts are quite cheap, buy dozen and practice sawing slots .  Seriously you can do one up with a medium thickness washer, mark where the hole is, saw / file one slot and if its a bit out vary the washer thickness.  Sorted.

[paintingsteve123]

Strange you should mention taps and dies as I sent my gearbox to JB restorations to check it out because when I took it apart for vapour blasting I found 4 what looked like crank case shims. They charged me £250 , changed a few bits inside so I thought that was quite reasonable.
I'm afraid I've digressed a bit their.
I've just bolted the gearbox back on yesterday and decided to run a tap into the 2 threads that hold the gearbox to the frame .
Yes I did snap a tap off , took me over 3 hours to get it back out.
Live and learn as they say and note to self stop being so bloody heavy handed

[paintingsteve123]

That's a good idea with using plain nuts
Just need to learn to cut a straight line with a hacksaw 🫣

[Rex]

Yes I did snap a tap off , took me over 3 hours to get it back out.

The fact that you did get it out is quite a result, but how come you were using so much force?

[paintingsteve123]

You know sometimes when you think , just a tiny bit more thats where I was at that point.
Also brute force and ignorance seems to go hand in hand.💪

[Rex]

Fair do's..
We've all done it.

[limeyrob]

Breaking taps is too easy. It takes time to really get a feel and know when to back off.  Tapped 3BA in the Concentric for a pilot jet, cold sweat all the way, you only have to loose you balance its toast.  Take it steady and feel each chip, no matter how slow you go its 10x quicker than getting a broken tap out

[groily]

That's a good idea with using plain nuts
Just need to learn to cut a straight line with a hacksaw 🫣

Cutting diisc (thin) in a dremel is also good for slotting, or a slitting saw in a lathe for those who have access and want 'perfick'!