Switch Mounting Box Threads Worn Ask questions and find answers to many subjects relating to electrics and electrical work

[gustoff1979]

Hi there. I have a wee bit of a problem. I replaced a light switch with another and while doing so managed to wear out the threads on the metal mounting box. Unable to remove the box and the thread mounts are part of the box so I can't replace them either.

Need to find a way to fix the threads! Help! My switch is currently hanging out of the wall! lol. :oops:

[ericmark]

I normally re-thread to 4mm instead of normal 3.5mm and change screws if they will fit through holes in switch. Or change back box if not or in a position were 4mm would not look right. Re-threaders are available in both 3.5 and 4 mm in most electrical whole sale outlets. Last one I got were from City Electrical Factors.
Eric

[speedygonzarlis]

i always keep a box of screws for just this fault, you need size 6 x 30mm from your local ironmongers they simply selftap the cross threaded hole and the screwhead is exactly the same so looks crackin!

[ericmark]

I think speedygonzarlis has got sizes mixed up. Standard size is 3.5mm and going up to 4mm may work although I would tap out as most 4mm are brass and backing box is steel so unlikely brass will cut it's own thread in steel. Often it is only the screw which is damaged by some grit stuck to backing box and to re-thread to 3.5 often works i.e. knocks of grit. I buy packs of extra long 3.5 screws for when backing box is too deep so I always have spare short screws in my box. And conduit boxes use 4mm screws so I also have 4mm screws in my box. But replacements always come from electrical whole sale outlets as most ironmongers will not stock 3.5mm
Eric

[gustoff1979]

thank you guys!

[Wormhat]

Hi guys,
Ive curently got the same prob as gustoff1979. I would like to ask ericmark could he possiblly tell me the names of any elecrical wholesalers on the Highstreet, where I could pop in and buy one of these 3.5 or 4mm scwew threaders. The place you mentioned sounds as if it may be internet only. And its such a small item to pay p&p for, plus I always seem to want things now. Ive no patience I suppose.
Thanks in advance for that.

[ericmark]

Wormhat I did say CEF but most whole sale outlets will sell them it is only DIY shops who would not stock them.
Eric

[Wormhat]

[quote="ericmark"]Wormhat I did say CEF but most whole sale outlets will sell them it is only DIY shops who would not stock them.
Eric[/quote]Thanks Eric . Ive not done any electrics for about 10 yrs.Only vaguely heard about CEF.Having been on there web site I Now feel foolish .Its a huge company and I have found 10 outlets around 10 mile radius of where I live in Manchester, all on Trading estates.All easy to get to.

[Wormhat]

[quote="speedygonzarlis"]i always keep a box of screws for just this fault, you need size 6 x 30mm from your local ironmongers they simply selftap the cross threaded hole and the screwhead is exactly the same so looks crackin![/quote] I checked out The speedygonzarlis tip and Found he means;- No.6 screws. 30 mm long.[No. 6 being the catorgory used for sizes of self tapping screws is also used to catorgorize wood screws.They do not have a machined screw thread as with the Metric series] I can see that it looks like a good option, but [color=red]I would remove the sharp point which could Puncture an electric cable with disasterous results.[/color]Much better I think to buy a 3.5 or 4mm tap [ quote Eric = Re threader ]or get a new backbox.