Movable screw posts on light switch / mains socket backing boxes

What is the best way of securing the captive nuts on an electrical backing box for a light switch or mains socket?
I always find that if I unscrew the front screws (eg so I can paint behind the switch, or to replace a broken switch with a new one) I have great difficulty in getting the screws to mate with the captive nuts because they are often not fixed to the backing box but instead slide backwards so the screw can never mate with the nut.
Even if the screw does mate, it seems not to be secure and once I tighten it beyond a certain point it starts to jump thread instead of applying enough force to hold the switch against the wall.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Part stripped threads by the sound of it and screws too short.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 12/06/2019 19:48, DerbyBorn wrote:

My guess that the back boxes are set too far back from the surface of the wall and the screws are too short for the task, especially true where a wall has been tiled. I learnt a long time ago to have a supply of longer screws.
--
mailto : news admac myzen co uk

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Agree with the idea of longer screws but it sounds like you have cross thre aded the screw holes in the back box. A re-threading tool should help to re store the threads but in my experience this is a once only solution. On one s that I have re-threaded the screws have gone in and gripped but generally the result is quite a sloppy fit and certainly looks like it will not take another re-thread. One possible solution to stripped threads that I have c onsidered is using anchor nuts but don't know if you can get 3.5mm. The fin e threads on back box screws are notorious for cross threading the ones I p refer are the type that have the protruding core diameter before the start of the thread, these I find easier to centre and less prone to cross thread .
Richard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 13/06/2019 09:18, Tricky Dicky wrote:

Well there are these
https://backboxsaver.com/
Never used them.
However for a pro bodge job on a back box with a knackered lug that will not rethread you simply strip out the cores of some .75mm flex and wrap them through the hole several times before refitting the socket.
--
Adam

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've got some 3.5mm nuts. Just superglue to the back of the lug.
Handy for old boxes with BA threads.
--
*People want trepanners like they want a hole in the head*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 14/06/2019 00:33, Dave Plowman (News) wrote:

You need to be accurate when glueing.
--
Adam

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thursday, 13 June 2019 19:43:00 UTC+1, ARW wrote:

as expected, silly price

Neater than using a woodscrew.
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 14/06/2019 14:16, snipped-for-privacy@gmail.com wrote:

And then there is the other bodge when when lug is missing.
5.5mm hole though the back box where the eye of the lug was, stick in a red rawl plug and use a long 3.5 screw into the red plug.
--
Adam

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote in

Squeeze the lug with some grips to slightly squash the hole.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 12/06/2019 19:16, NY wrote:

Use longer screws. Don't overtighten.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How odd, I don't think I've had that issue. They are surely either captive or moulded in. Most of my problems with light fittings and switches are that the plastic ones tend to be so brittle they crack as you do that final quarter turn.. grin. Brian
--
----- --
This newsgroup posting comes to you directly from...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That was actually the quarter turn *after* the final quarter turn!
--

Roger Hayter

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Quess you mean plasterboard switch boxes, you could slide the screw post forward and put some tape behind it and don't push too hard on the screw until it catches the thread.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes that's what I'm going to do: either tape or glue the post in the forward position and check that the screw (OK, bolt) threads itself cleanly into the post (without cross-threading) with the faceplate removed, before fastening it normally.
Sod's Law: it would be the three-gang two-way switch that has the fault, so there are a *lot* of very stiff wires to cram back in as I push the faceplate back into place.
Why is it that backing boxes are designed with the captive nut on a movable slide rather than being securely moulded to the side of the box? It means you have to use much longer screws than normal to account for the nut retreating as soon as the screw touches it. All the boxes I've seen have either had a metal or plastic slide which is separate from the metal or plastic of the box, and rather loosely attached so it is prone to sliding.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's so you can set the faceplate horizontal even if the backbox is slightly skewed in one plane or another.
--

Roger Hayter

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dunno where you found a box like that, Adjustable lugs are designed to allow a switch to be set square in a squint box. Not to move away from the fitting.
Most these days have one fixed, one adjustable. Do the adjustable one first. A torch may help to see things.
--
*I'm out of my mind, but feel free to leave a message.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.