A7 thread formats.

[Brandis]

I'm going a bit nuts here in the land o' cotton.  My A7 engine came with no nuts and bolts.  Given that my last project was an M20, I expected the need for BS coarse and fine with some cycle thread in there just to drive us colonials a bit nuts.  But there appears to be UNF(?) and other ones not identified.  I realize I need a thread gauge with more options, but . . . .
Do I just wait for my parts book and order all the nuts, bolts and studs off those part #s ?
I knew it's heresy but there are times I pine for my old Triumph Speed Twin.  Or my old WWII Harley with one thread format that I could buy in the farm tractor section of any hardware store in Nebraska.

[groily]

This, from a link supplied a while back by Muskrat, under the 'Service' blah blah section of the forum, is a good starting point:
https://draganfly.co.uk/product-category/bsa/sparesparts-for-bsa-a710-b3133-c101112-m202133/fastenings-bsa/
There's more Cycle than anything else, typically, and British makers only started using some Unified stuff in the '60s. Not sure what there might be on yours - but in any event folk will use what they can get where it's 'just' a nut 'n a bolt. Here in France, a lot of metric gets used, not surprisingly  . . .

[Greybeard]

most of your engine purchases will be case screws, with a what I call a cheesehead, that may not be the correct term.

Phillister, not Cheesehead

[RichardL]

If that plain shank is longer than about 0.29" it could bump into the threads  in the inner cover for some of the timing cover locations.

Richard L.

[muskrat]

G'day Brandis.
Another two links to look up http://stainlessbits.com/link12.html and https://www.motalia.co.uk/
I don't know about over there but here I can go to the local push bike shop and get 5/16 and 3/8 cycle thread nuts and axles to make my own.
Cheers

[muskrat]

G'day SHM.
Back in the early 80's when I refurbed the plunger I used a lot of them, and most are still there!
Everything in Oz is tougher 
Cheers

[KiwiGF]

I'm going a bit nuts here in the land o' cotton.  My A7 engine came with no nuts and bolts.  Given that my last project was an M20, I expected the need for BS coarse and fine with some cycle thread in there just to drive us colonials a bit nuts.  But there appears to be UNF(?) and other ones not identified.  I realize I need a thread gauge with more options, but . . . .
Do I just wait for my parts book and order all the nuts, bolts and studs off those part #s ?
I knew it's heresy but there are times I pine for my old Triumph Speed Twin.  Or my old WWII Harley with one thread format that I could buy in the farm tractor section of any hardware store in Nebraska.

You definitely need a thread gauge…one that does TPI (to cover BSW, BSF, BSC, UNF, UNC, BA) and also metric 🤬  as you will find all of those on yer average BSA. Lucas components do not stick to the BSW/BSC convention BSA used in the 50’s.

You can spend a lot of money getting the fasteners “correct”. Some you “must” get correct to avoid damaging the thread on a costly component (cranks, cases etc).

Aftermarket components (rear foot rests come to mind) often have incorrect threads, UNF or metric.

I bought a selection of “generic” new long fully threaded BSC bolts from british bike parts suppliers and then cut them down to length as required, but eventually bought a few of the most common BSC dies and taps to “convert” bolts with plain shanks to BSC etc

[muskrat]

Good one SHM 
I painted mine black
I'm pretty sure the axles and nuts are grade 8 so good for cycle parts and the nuts are flanged to eliminate washers.
The axles can be cut down to make bolts with a nut "glued" to one end.
A few have been on the bike for 40 years.
Cheers

[Swarfcut]

 BSA's Heritage was in Bicycle manufacture, and a fine thread designed to resist vibration was the background to the Cycle Engineers' Institution/British Standard Cycle Thread format in general use in the industry. Hence most of the major fastenings are CEI/Cycle thread. Threads into alloy are the coarser Whitworth thread, many of the studs have Cycle at one end, Whitworth at the other.

 Draganfly's online parts catalogue will allow you to identify the part numbers for the various fixings. Thanks to Musky there is also another handy nut and bolt chart in the Literature section, cross referencing part numbers to thread form so at least the thread originally used can be identified.

  A few cheap  carbon steel Cycle and Whitworth taps and dies will be fine for cleaning up the old threads. Sets of chaincase and timing cover screws are readily available here in the UK as are the majority of studs and bolts. Cylinder head bolts are not Cycle, BSF springs to mind....(Confirmation needed).  Lucas stuff was generally BA Thread, still used in the Electrical Industry.

 Swarfy.

[BSA_54A10]

And just to confuse you Americans
UNC & BSW have the same TPI over most sizes commonly found on BSA's
However the unified threds are cut deeper into the bolt so you will damage crankcases theaded BSW if you screw UNC  bolts in there and they will always be working themselves loose .

[Brandis]

In 1975, I was on Baffin Island at an abandoned Cold War radar station.  They used RCAF Lancaster bombers to fly in the huge amount of cement.  There was one crashed a quarter mile short of the runway.  Ran out of fuel, they said.  It was pretty intact and I stripped some hardware off one of the Merlin engines for my Vincent and Manx Norton.  Everything fit perfectly.  If fewer thread formats can win WWII . . . . . ?

My M20 is a lot simpler in the thread dep't. Presumably the MoD wasn't in the mood for pointless complication.  Why did BSA abandon that approach on the A7?

My engine has literally no nuts and bolts on it.  I'm told my parts catalogue will arrive when the crankshaft does.  The fun will begin.

[RDfella]

However the unified threds are cut deeper into the bolt so you will damage crankcases theaded BSW if you screw UNC  bolts in there and they will always be working themselves loose .

'tis the other way around - Whit threads are a fraction deeper than UNC, but only by a whisker (less than .002" on 3/8" dia). What is more important is the difference in thread angle, BSW being 55* and UNC 60*. Beware too the 1/2", where they differ in pitch - one is 12tpi and the other 13.

[Greybeard]

In 1975, I was on Baffin Island at an abandoned Cold War radar station.  They used RCAF Lancaster bombers to fly in the huge amount of cement.  There was one crashed a quarter mile short of the runway.  Ran out of fuel, they said.  It was pretty intact and I stripped some hardware off one of the Merlin engines for my Vincent and Manx Norton.  Everything fit perfectly.  If fewer thread formats can win WWII . . . . . ?

[Triton Thrasher]

  I stripped some hardware off one of the Merlin engines for my Vincent and Manx Norton.  Everything fit perfectly. 

Hardware shmardware!  Did you get the platinum points?

[Greybeard]

In 1947 I was in Roswell, New Mexico in the proximity of a crashed Alien Craft.  It was dark.  I was semi-conscious and confused, lying in gravel.

I managed to strip some hardware for analysis, a papery silver fabric in a tough wood pulp box.

Several hours later, as the sun rose, I recovered sufficiently to realise that I was in the front garden of a terraced house holding an empty fag packet.

Last time I ever drank Aguardiente.

What are you like! 😜