Making an electrical screw thicker / more grip ?

[Bobballs]

I needed to replace a light switch, it doesn't have a metal box behind it but an old wooden one with a separate metal fitting to attach the switch to. The threads on this fitting for the electrical screws seem to be gone as when I screw the electrical screw in and get tension the fitting pulls away from the screw.

The fitting is old and I want to avoid putting new metal box in as old wooden one is plastered in and I can't get hold of a new metal fitting. Is there anything I can do to give the screw more grip as they all seem to be the same width?, I tried wrapping a small amount of electrical tape around the screw which gives it more grip but I still can't get the new socket tight against the wall.

 

[redpis]

Is it possible to tap out the worn thread with a slightly larger one, maybe to accept 4mm?

 

[TicklyT]

Old electrical fitting used to have 4BA threads in them. If someone has mashed a metric 3.5mm screw into the hole, then the thread is probably stripped. A 4BA screw is a fraction larger, but probably not large enough to hold in a damaged thread.

If the thread is in a sheet metal lug, it can sometimes be tightened up a bit by squeezing it with a pair of pliers.

Otherwise, either fit a threaded spacer pillar and trim the screw to length, or tap the thread out to 4mm and fit a larger screw.

 

[JohnD]

can you post a picture of it?

 

[foxhole]

To improve fit drop a single staple thru hole and pinch, then a suitable size wood screw or self tapper should hold.For larger worn metal fixing I put a short piece of wire thru hole [paper clip often works].