BSA C15 cap screws

[Mascott]

I am a new member so apologies if I have posted this in the wrong section.
Help needed, I have recently  taken ownership of a 1960s C15 ( with distributor) the last person to work on the engine was a complete butcher,  that aside I a missing some gearbox cover cap bolts.
What size thread on these? The outside diam is about 6.2 mm and approx 26 threads to the inch.
Where would I source these preferably stainless.

Also someone should not have been let loose with a hammer as there are lots of hammer rash scoring on the crankcase and covers, what would be the best way to clean these up?

Thanks in advance.

[chaz]

you need to go shopping...
https://www.draganfly.co.uk/bsa/bsa/c15

if you have a 6" bench grinder I use scotchbrite wheels. not cheap but polish out well.
https://www.cromwell.co.uk/shop/surface-conditioning-products/surface-conditioning-products/scotch-brite-deburring-wheels/f/3307

[Mascott]

Thanks but what type/size threads having lots of difficulty identifying this thread.

[chaz]

sorry, but engineering knowledge helps with bike restorations...
the majority of threads are BSC Cycle up until the main customer was America when they changed to Unified UNF and UNC.

6.2mm equates to 6.35 or 1/4" therefore you have 1/4BSC 26tpi.
there is a slight problem as many suppliers will send you BSF Fine threads, same pitch ie 26tpi but BSC are 60degree and BSF are 55 degree thread angles.

navigate through https://britishfasteners.com/threads/bsc.html

[DAVE BRADY]

Hi,

Some threads are BSW, a course thread, especially when going in to aluminium cases.  Like Chaz said, contact Draganfly, also C&D Autos may be worth a try.

Draganfly has a good website with parts illustrations and part numbers.  C&D Autos does not have a website but are very helpful over the 'phone. Their number is in The Star.

Dave.

[Pete A10]

Hi Mascott,
May be good idea to get a parts book as this gives part numbers for all the parts including nuts and bolts. There is a website -www.bsaunitsingles.com. If you go on the home page, at the bottom there is a highlighted item "spares manuals" which takes you to a listing of all the various unit singles and allows you to download a pdf of the parts book. There is also a link on the site which takes you to - www.stevenott/bsatrinbw.htm - this is a listing of all the bolts and nuts used on BSAs referenced by their part number and gives size, thread type and length. The list is not totally complete but it is extremely useful in identifying what size bolts are required.

[Mark B]

Mascott, as others say, make friends with Draganfly. They're very knowledgeable and helpful over the phone, and their website has all the parts diagrams which show the part numbers.