What size blanking plate for this small back box

Box as a hole is smaller, but Isn't the critical dimension between the centres of the mounting lugs? 2 3/8" in old money = 60.3mm, looks rightish allowing for whatever parallax error exists in your photo ...

Yes, good point. Maybe the standard blanking plates will work after all. I'll give it a go. Thanks.

Nice nails

Bill

A surface mounting socket blank plate is smaller than one to replace a flush one. But has the same fixing centres. Surface mount boxes have rounded 'corners'.

Looks good to me - apart from what looks like a snapped off screw in the left hand lug

I assume you are talking about the MK metalclad stuff?

Looks like a standard size single box to me.

It also looks quite old. The standard screw thread pitch changed a few decades ago, and you may need the old type rather than current screws.

If all you are doing is hiding them, I guess a couple of fishplates made of a couple of bits of tine could be all you need, slightly cranked at one end to allow the screw head to be screwed down and a self tapping screw at the other outer side for the normal blanking plate. Brian

my tool box has an M3.5 tap to 'modernise' old boxes.

All the black painted back boxes I have come across are old imperial types. Modern sockets and plates do cover and match up but you will find the tappings are 1/8? but running a 3.5mm rethreading tool through them will allow current screws to tighten.

Richard

Pretty well any make metal clad surface mount.

I've no experience of surface mount plastic. ;-)

They used to be 4BA !

My tool box has an M3.5 tap to rescue cross-threaded back box threads :-).

This seems to occur more often on a plastic box for flush fitting in a plasterboard wall.

Definitely 4BA

Bill

I'd have hoped since we've left the EU we could go back to good ol' British Association screws. Instead of that metric rubbish. And, of course, re-design BA totally so it wasn't metric based.