Two bee eh all round.
Can anyone confirm the thread size of the rear trigger guard screw for a Superstar / Meteor and other models? I am carrying out a little cosmetic work on a Superstar and the screw is a bit 'challenged cosmetically' although does work. I have tried various screws from my collection but failed to find a replacement. Searching around on this forum and the internet in general leads me to the conclusion it could well be UNF 8-36.
I know I could buy a new one but that irks me a bit although to be fair, a search for unf 8-36 screws shows they are not very cheap anyway.
I am told you can re-tap to 2BA but I see no need to do that. It might be more fun to get a 8-36 die and cut a new thread on a slightly oversize screw.
Interestingly the front stock screws can be replaced with 4mm although I doubt that is the original size.
All help appreciated.
Cheers, Phil
Two bee eh all round.
I tried googling this a while back and just bought (last week) of John knibbs. Think it was a fiver posted. Like you I tried dozens but I'm not technically minded so just bought that incase I screw the thread up
Sorry but they are not. I tried a 2BA bolt in the rear guard just to see and it is not the right size. I found a thread somewhere that informed me that the manufacturer's thread could be retapped to 2 BA quite easily though. Maybe that is what you have come across. And the front stock screws are certainly not 2BA. 4mm fits but I doubt if that thread form is the original spec.
Cheers, Phil
M5 in my Supersports and Superstar. Thats the rear trigger guard screw, the fronts are M4.
This is getting more puzzling. Thank you evert. I tried M% but it was too big ... pity as I have a lot of them.
I am wondering if the best solution is to strip the action and re-tap the thread.... and put a nice screw in place.
Cheers, Phil
At the same time ... if someone has an electronic version of the Owner's Manual, I would be very pleased to have a copy.
Cheers again.
Last edited by Phil Russell; 29-10-2020 at 07:29 PM.
So, after making this duboius assumption based on memory and a bunch of mixed up supersport parts, I realized that my contribution would just add more confusion. So I went and actually measured some screws on some guns:
Late Supersport (presumably Birmingham made):
Rear: M5X0,8
Front: M4x0,7
Early Mk2 Supersport and Superstar:
Rear: measures in at about 4,6mm, and the thread pitch is VERY close to 0,7, and does not match up with any of my TPI gauges.
Front: M4x0,7
I measured a mk3 Meteor too:
Rear: the same as the early Supersport and Superstar
Front: not measured today, but earlier confirmed to be a 2BA (I actually made some screws that I threaded with a 2BA die for a meteor a while back.)
I must admit I've not had to source screws for later guns,up to mk6 meteor, 2 and 4ba used.
I can confirm that my Superstar, Supersport, Goldstar and even mk1 Lightning all have a 2BA x 1.5” rear guard screw. Front stock screws are all M4. It’s not uncommon to see different fasteners mixed and matched, Webley did exactly the same.
Cheers
Greg
Well, thank you all for taking such trouble. I appreciate it. I wonder which thread the Knibbs part is.
I am warming to the idea of retapping the thread now....
Cheers, Phil
Measuring the screws and relating to the BA thread system got me confused, so I had to learn more about it.
Its a British standard, so I expected the pitch to be imperial - but none of my imperial thread gauges matched the pitch of the early Supersport/Superstar rear screw. (clearly not a 30TPI, almost a 32TPI). The closest thread gauge I found is a 0.8 mm pitch - on a British thread system???
Time for some googling!
This page cleared up my confusion:
https://journeymans-workshop.uk/baandme.php
So, the table lists the 2BA as .185" diameter x 31.4" TPI!!! That does not really sound logical..
But the text goes on to explain:
"British Association threads were a metric thread system devised for small screws. Originally included even smaller sizes intended for use in watchmaking but these have been superceded by specialist horological thread series. Not metric like you might expect, but with diameters determined by a factor proportional to a power of the logarithm to the base 10 of the thread pitch in millimetres. Hence the rather strange mix of metric and imperial in the above table."
Aha! Dividing 25.4mm (1") by 31.4 TPI gets you 0.809, so the close to 0.8mm pitch starts to make sense.
The 4.6mm I measured with worn calipers is close to the listed .185", which translates to 4.7mm.
Its a confusing (when compared to more recent thread standards) system, but the 2BA really is close to a M4.7x0.8 thread.
Which is good for re-tapping to a M5x0.8 thread!
Last edited by evert; 31-10-2020 at 07:51 AM.
Having stripped the relevant block out, I find a 2BA screw fits. Why a 2BA would not fit with the block assembled on the rifle in the first place I do not know. if this thread is really 2BA then it could explain the untidy appearance of the guard screw fitted. Maybe this screw was forced into a 2BA thread???
Whatever ... onwards.
I continued my look at the rifle by stripping it. Not too bad really but the spring guide was a pretty loose fit in the spring and the large circular end broken off. New guide is being made. Small O ring breech washer was somewhat damaged BS 010 seems to fit OK in the recess but I do not have the larger O ring. I think it is OK though. Mainspring seems fine... must measure it, as it the piston seal. I will also add a piston sleeve.
So next ... trigger reassembly. Why do I expect coffee to be in demand?
At least it is raining here so I would not be outside anyway.
Cheers, Phil