(BA) screw British Association

BA thread, British Association, machine screw used on Lucas electrics, Smith Instrument, trim and all pre 1960 Jaguars. Numbers range for 1BA Smallest to 10BA the largest. Jaguar Parts manual will list #BA + the second number is the lengths in1/8 of an inch. ie: 2BA 4 is(4 X 1/8 or1/2 inch long, 6BA 2 is 1/4 inch long. 4BA 1 is 1/8inch long.
A good source for BA (machine screws), Whitworth (course),and BSF (British Standard Fine) is British Tool & Fastener. they also have taps, dies and tools.

I don’t want to be picky but BA threads are the other way round - 0BA largest at 0.2360 inches diameter,1BA 0.2090", diameter then reducing in size as their reference number increases - e.g 10BA 0.067".Theoretically they go as small as 16BA which is 0.0310" dia but 10BA is probably the limit for practical purposes.


Learn a fact a day: never knew what the “BA” represented!

thanks, for my obvious inverse error.

thanks, my obvious error.