gearbox cover plate threads

[RDfella]

Just a quickie - S/A A10 gearbox - what are the threads that hold the clutch adjuster cover plate in place? BA? Seems somewhere between 1/4 and 5/16.

[berger]

RD i tink they are 5/16 BSF but i've had some black&tans or even that is wrong i tink 1/4 bsf , someone will know and i'm not going to a cold garage to find out. haha i had to open some stripped ones up to 5/16 so i tink 1/4 bsf

[jhg1958]

I thought the A10 used cycle thread on steel and whitworth on alloy so I would expect them to be BSW.

John

[berger]

i still think they are 1/4 bsf , but i did not go to the pub i got  like that staying in, my boxes could have been messed with i know i messed with one box that wasn't very well. goodnight done it again

[CheeserBeezer]

i still think they are 1/4 bsf

Correct, 1/4 x 7/16 x 26 t.p.i. BSF and BSCY are both 26 t.p.i. at 1/4"

[berger]

i'v got it the beer said one is 55 angle and one is 60 and that could be why they fit but not as they should and then people like me see them nearly stripped and then go gung ho up to 5/16th

[RDfella]

Thanks for that.
Own threads may have been 1/4" originally, but not now. 1/4" slides in, and 5/16" doesn't seem to want to enter, hence my 'between 1/4 & 5/16' comment. Will get the loupe on it and try to figure the tpi, otherwise I'll put a 5/16" UNC tap through it. Tired of cutting down metric bolts to make BSF ones (had to make a dozen or more for the rocker covers).

[Rex]

Wot? Why not just buy generic BSF fasteners or even BSA original patterns?

[Swarfcut]

 This is possibly the only application where BSA did not use a BSW thread into alloy.

 The Screws are part 24 7178, and thanks to Musky's Nut and Bolt Chart

       https://www.a7a10.net/forum/index.php?topic=9222.0

 identified as 1/4" CEI 26 TPI X 7/16" long.   Also see CB's post above.

  I wrecked a cover thinking it was 1/4" BSW, cracked off the side of the lug. A worn thread may just hold by using a new screw, most threads here after all these years are marginal at best...as in RD's example.

 Swarfy.

 

[RDfella]

"Wot? Why not just buy generic BSF fasteners or even BSA original patterns?"

Ever tried that? First of all, regarding the heads, they're AJS, not BSA. Secondly, the rocker cover bolts are quite long, at around 3"
Trying to find BSF bolts of correct diameter & length is virtually impossible. Love the thread, but it's rocking horse poo now. Even AF / UNC ain't too easy to get, especially in Allen capheads, which is why I often resort to metric. Don't like metric threads, but sadly we're living in the 2020's and not the 1950's and things are what they are. In my view, most things were better back then.

PS - haven't sorted the gearbox threads yet. 1/4" is out of the question - I can push 1/4 bolt in by hand. Due to the lack of space in the cover plate for 5/16 hole & head, might helicoil to m6 (I have some) - provided I can sort that without having to remove the end cover to dispose of the tang (I don't need the extra work).

[BVSR]

Hello!

I have used Nooky´s:

https://www.nookysnuts.com/catalogue/screwsets/bsascrewsets/bsascrewsets.html

Regards Markku

[Angus]

Hi Tom who runs Nooky's lived over the road from me  . He sometimes uses my A7 & A10 to check fitment of parts.

[Rex]

So you're to blame then?
Only joking, Nookys are very good.

[RDfella]

Finally sorted.
Clearly the small cover wouldn't entertain 5/16" so I opted for 1/4" helicoil - m6. Why metric? - because I have most metric helicoil kits and the screws in stock. Having spent £200 on a new Dunlop rear tyre and a fortune on other parts, am now trying to be economical.
This is not a concours BSA, it's a vee twin special and there's a mixture of CEI, UNF, BSF and metric anyway.

[berger]

rd fella my end cover took 5/16 bsf with enough meat left maybe my casting had a bit spare. at least you sorted it