Back box lugs and cross threads.

[FatAlan]

Is it worth while re tapping lugs on back boxes? Just ordered a 3.5mm tapping tool as I had an issue at the weekend with the head of a screw shearing off and the resulting pain in the neck hassel of getting the remaining screw shaft out of the lug. This must be a very common problem. Is re tapping effective bearing in mind there isn't that much metal there in the first place?

 

[Rpa07]

Everyone remembers their first knurled screwdriver handle!

 

[FatAlan]

Had to laugh the other day when my son came home from school with his laminated plastic key ring. Some things never change!

 

[Dave OCD]

The M3.5 tap is also useful when plasterers of today fill up the lugs with cr@p, as well as a fair bit of the box. There was a time when they cleaned boxes out really well but that seems a rarity these days.

 

[VoltzElectrical]

I carry M3.5 and M4, and yes they are invaluable. As mentioned, if the screw 'pops', then compress the lug slightly then re-tap. At the moment I am retrofitting bollards in a caravan park whereby I remove the top half of the attaching plate, leaving the bottom half of the plate attached to the part in the ground. This leaves me with an 8" flat plate with the cable coming through, which I then drill and tap to accept M10 bolts for the new bollard. Oh, and did I mention it was raining.

To make matters worse, the old cables were terminated into 4" metal boxes that don't fit into the new bollards so i also have to grind these off before reglanding the SWA into galv U-boxes with a flex outlet.

Oh, and did I mention it was raining?

 

[telectrix]

so you got wet. think anyone cares? i don't .

 

[Dave OCD]

so you got wet. think anyone cares? i don't .

I wouldn't imagine you work as a Samaritans volunteer Tel ?

 

[westward10]

so you got wet. think anyone cares? i don't .

Why was it raining

 

[sparksburnout]

The M3.5 tap is also useful when plasterers of today fill up the lugs with cr@p, as well as a fair bit of the box. There was a time when they cleaned boxes out really well but that seems a rarity these days.

Blimey you must have had polite spreads down there, I reckon the b****s do it on purpose. I usually coil the cable all the way round the rim of the box, helps a bit. What I hate is when the builder cuts the board too big so you end up with a thin rim of plaster round the box that cracks and looks crap when you do your second fix.

 

[Dave OCD]

Blimey you must have had polite spreads down there, I reckon the b****s do it on purpose. I usually coil the cable all the way round the rim of the box, helps a bit. What I hate is when the builder cuts the board too big so you end up with a thin rim of plaster round the box that cracks and looks crap when you do your second fix.

Me too ! Despite our best efforts we're often at the mercy of idiots.

 

[uksrevivor]

I may be wrong here but the older back boxes had a different thread imperial if im right which when you use the newer faceplates on them the newer faceplates have metric thread screws 3.5mm which are different and can strip the older boxes thread.
I always use the 3.5mm re threading tool on old installation boxes and nearly always have to use it on second fix after the bloody plasterer has filled me boxes with plaster lol

 

[Marvo]

If the damage to the original thread is bad you can drill it out and use a 3mm clinch nut (AKA rivnut) and manually tap it out to 3.5mm after you've inserted it. You get aluminium clinch nuts which are easier to re-tap because they're softer than the usual electro-galve steel variety.

 

[rsgaz]

older back boxes had a different thread imperial if im right

It was 4BA thread (≈3.61mm) so it was slightly larger and had slightly fewer TPI also.

 

[Flanders]

Yes as others have said its a must have tool, Just be careful you dont snap the tap off in the lug
You will find you will use it a lot,.
it does anoy me when someone has just powered in a screw without tapping it out first, then i come along to replace the socket / switch and spend a age trying to unscrew it , untill it breaks off

 

[VoltzElectrical]

so you got wet. think anyone cares? i don't .

No, I took my huge fishing umbrella and sat perched on my tool box with the van radio on lol.

One repair I had to do was supposed to have me remove a double deep backbox from a tiled kitchen wall in a school kitchen for a cooker switch because the lower £.5 had snapped off. It would have been a helluva job to get it out the wall with the cables entering top and bottom so I snipped the snapped screw as close to the fixed lug as possible, then filed it flat smooth, re-drilled it, tapped it, and popped a new socket pin in, jobs a goodun.

 

[westward10]

It was 4BA thread (≈3.61mm) so it was slightly larger and had slightly fewer TPI also.

These must be seriously old, 3.5mm been about for decades (don't know how many though).