Broken screw thread

[pk_1314]

Does anyone know of a solution to repair a broken screw thread in an electrical back box that is in a tiled wall. Really want to avoid digging the box out of the wall.

Very annoying.

 

[JohnD]

do you mean the thread in the tab?

What do you mean by "broken?"

has the tab broken off? Is the tab present but the thread stripped? Or do you mean a screw has broken off in the hole?

photo might help

 

[securespark]

If the screw has broken, get a pair of pin nose pliers and try and screw the remains out from behind the tab.

Failing that, drill it out with a 3mm bit. Then rethread the hole with a 3.5mm tap.

If the thread has stripped, rethread it with a 3.5mm tap.

If the tab has broken off, you can drill a hole in the back box and thread that with a 3.5mm tap.

If the rethreaded hole will not hold a 3.5mm screw securely, then rethread it with a 4mm tap, then use a CSK 4mm machine screw.

3.5mm tap: http://www.screwfix.com/p/c-k-rethr...gclsrc=aw.ds&dclid=CIry0oDLuNUCFUzIUQodJRMO0g

4mm tap: http://www.screwfix.com/p/c-k-rethreading-tool-m4-x-0-7/23881

Edited to change link.

 

[PrenticeBoyofDerry]

I have seen the back box savers, never used, but would be interested on comments of those that have.
http://professional-electrician.com/products/watch-back-box-saver/

 

[chris1982]

If you mean that the screw does not bite in the box (i.e. keeps turning when you try to secure it), here is DIYer's trick that worked for me: Put some nail polish on the thread before putting the screw in. This makes a little bit thicker but retains the thread, and you will be able to remove the screw again.

 

[PrenticeBoyofDerry]

I have seen the back box savers, never used, but would be interested on comments of those that have.
http://professional-electrician.com/products/watch-back-box-saver/

I would assume if this was a rigid lug, that it would be wise to pigtail the back box.

 

[Iggifer]

3.5mm tap: http://www.screwfix.com/p/c-k-rethr...gclsrc=aw.ds&dclid=CIry0oDLuNUCFUzIUQodJRMO0g

4mm tap: https://www.avontapdie.co.uk/m4x07-metric-tap-set

Doesn't really matter, but screwfix also do an M4 0.7 tap.

Those backbox savers are a good idea, but so damned expensive!!

 

[333rocky333]

Or use the old trick of squeezing the lug together to tighten the hole, then rethread it 3.5 or use a spare 3.5 screw to hopefully recut the thread

 

[333rocky333]

If you mean that the screw does not bite in the box (i.e. keeps turning when you try to secure it), here is DIYer's trick that worked for me: Put some nail polish on the thread before putting the screw in. This makes a little bit thicker but retains the thread, and you will be able to remove the screw again.

Must say thats a new one

 

[PrenticeBoyofDerry]

Those backbox savers are a good idea, but so damned expensive!!

Not just the item, but the P&P for such a small item seems extortionate.
How many come in a pack?

 

[333rocky333]

Discounts available on quantity orders:

Product Discount
(%) Price inc.
VAT (£)
BBS pack of 1 5.99
BBS pack of 2 11.98
BBS pack of 4 16.04
BBS pack of 5 20.06
BBS pack of 10 29.94

 

[securespark]

Doesn't really matter, but screwfix also do an M4 0.7 tap.

Done!

 

[FrodoOne]

If the thread has stripped, I would suggest the use of an "Epoxy Putty" such as http://www.jb-weld.co.uk/j-b-weld-epoxy-putty-sticks/j-b-weld-steelstik-epoxy-putty

As it says in that reference, "After mixing, it forms an industrial-strength polymer compound that can be molded, built up or used to patch and repair steel components. SteelStik sets in three to five minutes and after sixty minutes, can be drilled, tapped, machined, ground, filed and even painted." (While full setting may take 60 minutes, it is well past the stage at which it can be worked after 15 minutes or so.)

However, if mixed and molded behind and over the "lug" in which the thread has been stripped, it can be "tapped" while still soft by the use of the screw to be used.
If the screw is wetted with water and turned, the thread can be molded to the depth of several millimeters. When set, the threaded material behind the lug will act like a fixed Back Box Saver.

While this brand does cost more than a single Back Box Saver it costs less than two - and has many other uses in a DIY workshop.

Other brands of "Epoxy Putty" are also available.

 

[TheJay]

The reviews on that epoxy product are very mixed, there are a number of people who said it doesn't work very well and some specifically said it wasn't strong enough to tap.

 

[crystal ball]

If you mean that the screw does not bite in the box (i.e. keeps turning when you try to secure it), here is DIYer's trick that worked for me: Put some nail polish on the thread before putting the screw in. This makes a little bit thicker but retains the thread, and you will be able to remove the screw again.

Thats a good excuse to keep nail polish in the van, need a use for mascara now