4mm socket lug rethreader

Discussion in 'Electricians' Talk' started by sams, Feb 14, 2020.

  1. sams

    sams Member

    i know they sell 3.5mm socket lug rethreaders standard for the 3.5mm socket terminal screws .

    They also sell 4mm rethreaders , but where can you purchase 4.00mm socket terminal screws ? ive looke everywhere but can not find any.

    4mm would be convenient when a 3.5mm lug is damaged
  2. You can buy M4 countersunk screws in the length you require, but they will be surface on the switch or socket and not more or less flush like a 3.5mm.
  3. peter palmer

    peter palmer Super Member

    Do 4mm fit through the brass eyelets on the socket.
  4. Tony Goddard

    Tony Goddard Screwfix Select

    I don't think you will get an M4 through the brass eyelets, it certainly won't countersink. There are two threads used on socket back boxes, M3.5 and 4BA on older ones, 4BA is slightly fatter and has a coarser thread. It certainly won't look good, and the heads might stop plugs fitting flush on sockets as often the plug body covers the screw head, at least in part.

    If you have knackered back boxes and don't want to chop them out you can, if you are careful drill out the lug to 4mm, then cut a strip of tufnol (an industrial plastic) or nylon 66, both available on fleabay (don't use metal in case it moves and causes a short) just wide enough by an inch in height, drill and tap to M3.5 and glue to the back of the lug. The glue holds it in place for inserting the screw, and should that ever dry out, the rectangular shape means it can't spin if you unscrew.

    Hand re-threaders are available in all sizes, I've even got an M20 one for cleaning up conduit fitting threads. There is a firm called Hall in Sheffield that make the whole range.
  5. The 4mm does go through, but as I said in post 2 it will not be flush/countersunk like 3.5mm.
  6. spinlondon

    spinlondon Screwfix Select

    There are repair kits out there.
    Don’t know how good they are.
    Sometimes you can get the screw to bite, just by bending in the lug slightly.
    Screw goes through the lug at a slight angle.
  7. peter palmer

    peter palmer Super Member

    Easiest way is to crush the lug slightly with pliers so the hole goes oval and then re-thread with 3.5, is good enough to get a good hold of the screw. If its the adjustable lug it might be easiest to just replace it or if its the fixed size then remove an adjustable lug and put it behind the damaged lug. Or another idea is to drill the back of the box with a 2.5/3mm bit and tap that out using long screws.

    there are loads of ways of salvaging a back box before you rip it out of the wall.
  8. Philip Hyde

    Philip Hyde Active Member

  9. Comlec

    Comlec Screwfix Select

    Yeah, on Amazon for £11.45 for 4 plus £4.59 for 3day standard delivery
    *** it is an envelope with 4 small screws. Rip off postage at its best!
  10. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    TBH I just looked at this as it seems a great idea, ferk it, ill take the old box out and make good with fine fill after, what a rip off

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