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Discuss Repairing a damaged back box thread. in the DIY Electrical Forum area at ElectrciansForums.co.uk.

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  1. Pete E
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    Pete E DIY

    Location:
    N Wales
    It looks like the upstairs in the house has had some electrical work done in the past and I've been left with a couple of blanked off back boxes.

    On one of them, the cover plate is loose and looks a little unsightly. While attempting to tighten the screws up, I found the threads on each of the bushing are buggered....

    I am going to try to tidy the thread up by retapping with either a M3.5 or M4 tap.

    If retapping with the M3.5 does not work, will I need to re drill/clean the holes with say a 3.5mm or 3.6mm drill before trying to run the M4 tap through it or should the M4 tap clean it up ok?

    Thanks in advance,

    Peter
     
  2. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    or replace the back box?
     
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  3. pirate
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    pirate Regular EF Member

    Location:
    Glasgow
  4. pirate
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    pirate Regular EF Member

    Location:
    Glasgow
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  5. Gavin John Hyde
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    Gavin John Hyde Electrician's Arms

    Location:
    Somerset
    Business Name:
    Sulis Electrical Services Ltd
    Backbox saver has saved me a lot of time previously. The small cost outlay is saved in not having to replace a backbox.
    With some you can insert new screw plates that hook inside the back box.
    Another trick is put a blank plate on front and insert a long thin rod with a bit of paint on back and push until you reach the rear of box. Then drill this mark. Insert a plug and you can then use the long uncut machine screws to fasten socket. Switch etc
     
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  6. camerabloke
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    camerabloke Electrician's Arms

    Location:
    Northampton
    Squeeze the lug gently with pliers then retap 3.5 mm
     
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  7. Pete E
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    Pete E DIY

    Location:
    N Wales
    I don't really want to remove the back box as it might damage the decorating although I might remove and fill it at a later date.

    I have a tool similar to the CK one for doing this sort of thing, but the shaft is double sided, one side M3.5 and one side M4...As I recall M4 threads are used on the screws and bushings on metal conduit?

    Anyway, I'll give it a go running the 3.5mm through first and then if that does not work, I'll try the M4 tap....

    When I managed to get the existing screws out, it looked like somebody had tried to use screws with the wrong thread...they were close but not close enough.... the screws were also a fraction too long and were bottoming out against the back of the patress...
     
  8. Marvo
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    Marvo Admin and gender confused Staff Member Admin

    Location:
    South Africa
    You could also use clinchnuts (sometimes called rivnuts) but I've only seen them in M4, not M3.5. I'd go with the squishing the existing hole and retap to 3.5 advice. You could also put a blob of 2-pack epoxy glue over and into the hole, give it time to set then carefully drill the epoxy and retap to 3.5mm
     
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  9. westward10
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    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Top Poster Of Month

    Location:
    Northamptonshire
    Used a Back Box Saver the other day bit fiddly but did the job.
     
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  10. Des 56
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    Des 56 Forum Mentor

    Location:
    Gliese 581C
    You can play around re tapping and good luck to you

    90% of the time,if you follow the solution given by camerabloke it works just fine
     
  11. robd
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    robd Electrician's Arms

    Location:
    East Anglia
    Agree with Des
     
  12. Strima
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    Strima Electrician's Arms

    Location:
    St Neots
    I've just looked up the price of them and spat my coffee out all over my keyboard, they aint cheap...
     
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  13. Pete E
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    Pete E DIY

    Location:
    N Wales
    Thanks Gents..As I say I'll give the M3.5mm a go first as suggested and see where we go from there....
     
  14. westward10
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    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Top Poster Of Month

    Location:
    Northamptonshire
    Yeah the cost is outrageous but if you have a tiled in back box they do the job.
     
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  15. Tes369
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    Tes369 Regular EF Member

    Location:
    Cumbria
    If your feeling really kinky you can drill and tap the back of the back box :thumbsup:
     
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