Electrical socket screws - what size thread?

M 3.5 mm

M3.5

Pretty common, but most easily found at electrical wholesalers. They also sell rethreading taps with plastic handles which can be an absolute godsend for some repair work.

thanks

And isn't it Strange how M3, M4, M5 etc are common-as-muck sizes sold at quid-or-two-gets-you-one-or-two-hundred prices, while the 3.5s having more or less only this application are Specialist Items selling at 5 or more times that price? (Well, economics of mass mfrg being what they are, I s'pose it's not Strange. Presumably M3.5 was the closest in diameter in metric sizes to the Imperial size previously used (4 BA?) and it was considered more important to have only the backbox threads and accessory screws change, leaving the holes in accessory plates unchanged, than to use a widely-available size...)

Stefek

Yehbut they're raised head screws which always seem to be more expensive and rare. Ordinary 3.5mm pan or countersunk are easy enough to get.

And available in a variety of lengths from 'proper' electricians' suppliers.

I bet they dont do long versions of the slightly smaller headed screws that came with the new sockets I bought! I have put some standard longer ones I had in for the moment but the slightly larger head of the normal screws stops some plugtops going right up to the socket face. Nothing seems to be simple these days.

Sounds like you've bought some strange accessories. What make are they?

More likely strange screws. I got some "long" screws (50mm) from Screwfix heads are just a tad larger than the counter bore in the accessories. These screws also have a nasty slot/philips combination head.

easily shrunk if you have an angle grinder and drill. Careful not to damage the threads in the chuck though.

NT

I thought about a grinding wheel but dont have one - never thought about spinning the screw though, something to try :o)

Think they go under the name "Ultimate" or something - flat plate sockets from B&Q

Apart from most screws of this type being plated. ;-)

Perhaps the correct screws are just plain countersunk if the plate is shallow?

Curiously, BA sizes are in fact metric ! 4BA is 3.6mm diameter with a slightly larger pitch than M3.5. I've found you can use M3.5 bolts in old sockets, but not (obviously) the other way round. Perhaps this explains the odd choice of size.

Yes, I've often surprised people by telling them that. I believe they were a Swiss standard or soemthing originally.

how does that make a difference?

NT

They're plated for a reason. Durability and looks. Remove the plating round the edge will probably show after a while.