6BA round head screws required.

Here you go guys – try this lot. Very good service.

http://www.modelfixings.co.uk/index2.htm

TTFN,
Neil

In passing, I need a small supply of 3/16 UNF, either 1/2 inch or 5/8th

The head doesn’t matter. Ideally Phillips, Posi, or Allen key hex, but straight or even a bolt head would do.

Moggy

Sounds as though pagen01 has you fixed up.
I was going to suggest that size sounds like Meccanno screw size (although may be a bit more coarse than BA) but I do remember using BA nuts/bolts on model aero engines.

Roger Smith.

Hi Ritch, I can’t post links at the mo but if you type http://www.ba-bolts.co.uk/steelmd.html into Google it will take you to ba-bolts.co.uk listing of said screws.
They have those sizes listed as £1.44 per 10 screws.