Old imperial conduit box lid screws

[Aindowsimon]

Any one know the size of the old imperial conduit box screws ?? I don't have callipers. They look to me like 5/16" screws any help appreciated

 

[freddo]

I couldn't find a 11BA, 14BA, 15BA OR 16BA tap in this box, but I am sure I have them somewhere.

16BA must be tiny! I've worked with 12BA and that is small enough!

 

[Petej999]

16BA must be tiny! I've worked with 12BA and that is small enough!

2BA or 4BA not quite sure

 

[pirate]

That is the question....2BA or not 2BA

 

[Julie.]

16BA must be tiny! I've worked with 12BA and that is small enough!

16BA would be 21swg, so around 0.032" ~0.8mm in outside diameter.

Edit

Should have added, BA is based on swg sizes, so 2BA would be a suitable thread for 6swg (0.192") and will cut slightly below this (around 2-4%) to guarantee a proper thread 4BA would be 9swg (0.144") etc.

It was useful because swg would be widely known, and therefore an appropriate BA thread would be known and although they don't equate exactly it's like those snippets:

1/16" ~ 0.0625" ~ 16swg ~ 16BWG ~ 1.6mm

Essentially the old systems all lined up to work together in a practical way.

Of course this only works in imperial measurements, the American things like awg etc don't line up with anything at all.