Replacing a socket

It's not an unusual problem in my experience. It can take quite a while and a lot of bad language to get the screws in the holes. The 'one lug is loose and one lug is tight' is normal on some back boxes, the idea is that you can move the 'loose' one up and down a little to get the socket straight.

Persevere and you'll probably get there. It may be worth trying some diffferent (longer. shorter?) screws, they are all now M3.5 (and have been for many, many years) so you won't have the wrong thread.

Not sure what they were, but there have been at least two threads used, and probably the current one is metric. Not necessarily a whole number of mm. I've put some panel mounting sockets in over the last few years, and I believe they were M3.5, I just used the screws they came with.

I've always kept screws removed from old electrical stuff, and occasionally found a later use for them. I recently looked at screws in a curtain rail, as one had gone missing, and carefully measured the diameter and estimated the thread pitch. I was completely unable to find it among metric, UNC, UNF, BA or BSW charts, so there's still a screw missing.

I now have a set of drills and taps....for such occasions

I invested in one of these:-

New is M3.5 and I think the old type was 4BA. I'd reuse whatever screws there were on the old socket.

There are also tools for cutting a new thread in the backbox if you crossthread the old one:

Preparing for sale of my parents' house, I went round and did basic socket checks (with a Kewtech kt107) it found a couple of the original

So I replaced the sockets, found the new screws didn't fit, then the penny dropped they were the old 2BA(?) backboxes, rather than M3.5 so I just re-used the old screws, you can get a re-threading tool if you have lots to do

I was reusing but I wonder if the previous person used the wrong screws?

run a 3.5mm tap through the holes. That's the only reason I have one. useage not fouund elsewhere.

As do I, but this went into a fairly hefty chunk of stainless steel. I didn't fancy that.

You may now and then find an imperial thread (4BA?) backbox... running a socket tap through them usually fixes em!

Is the new socket faceplate slightly deeper than the one you are replacing? Sometimes it can just be the screw is not long enough to reach far enough into the lug when going through a thicker face plate.

You can also a "Repair tool" as the threads seem easily damaged .....

Dave

Presumably you've sorted it by now but I was going to suggest have you tried swapping the screws around? It's not too difficult to cross-thread one of the screws which "re-cuts" both the screw thread and the back box to some extent making a non-butchered screw unable to mate up with the "new" thread (either on the screw or the back-box).

No, it's not that. The screw is long enough to allow my small finger in to guide the lug. Not too long though as it stops turning long before it is fully inserted. It feels either that it is going in at the wrong angle (the screws seemed to come out at a slight angle) or that the thread is not engaging correctly. The oddity is that I reused the existing screws.

I tried that too when I realised one of the screws was getting damaged.

Welcome to the world of standards.

If you think that is fun, wait until you have to do any plumbing.

You can easily cut down longer screws with something like

Note: at times the cut part of the screw can be ejected from the tool at supersonic speed so just take care with use and use eye PPE.

Video

Screws too long for the back-box because your new socket is thinner?