How do you cut a 20mm hole in a metal box?

[slippyr4]

As above. I need an extra outlet for 20mm plastic conduit system from a metal garage CU, and there is no suitable knockout. Is there a special tool for the job? or do i need to drill & file for hours?

Thanks

slip

 

[plugwash]

use a holesaw, remember to drill a pilot hole first.

 

[breezer]

see this

 

[sparky40]

And turn the board off when drilling a hole is a good idea !
I have seen a file that a fellow sparks used on a 'tight-hole' so to speak, bus bar + file + panel = bang !

 

[slippyr4]

cool, i've got a hole saw. didn't realise they were good for metal - thought they were just plastic and wood type things.

thakns

 

[securespark]

You may have a hole saw that is only suited to plastic/wood. Check first, otherwise you'll make a right mess of the saw and your workpiece....

 

[ban-all-sheds]

You may have a hole saw that is only suited to plastic/wood.

I have to say, looking at the teeth on the one that Breezer linked to....

This is the type of tool to use: http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp;?SKU=024961

There are better ones available, e.g. RS Stock no. 543-579

 

[slippyr4]

I wondered if there'd be a punch type tool - i'd seen them for cutting tap holes in sinks before. Irritatingly I put an RS order in for work only this morning (

Not sure if the punch'd get through the CU - it looks pretty thick steel to me. I'll have a go with the holesaw tonight and if it's a no go then i'll have to get a hole cutter.

cheers

slip

 

[ban-all-sheds]

How did you get on?

 

[slippyr4]

hole saw did the job. i could only find a 19mm, so i had to file round the edges a bit. But it looks nice and neat now.

Bit annoyed that the CU didn't come with more knockouts. It's a wylex, and it had 2 20mm on the bottom and a much bigger one - about 40mm maybe, on the top.

My armour comes in one of the bottom holes and i wanted a 20mm on the top for conduit. Now i have one.

thanks

slip

 

[simon_d]

hole saw did the job. i could only find a 19mm, so i had to file round the edges a bit. But it looks nice and neat now.

Bit annoyed that the CU didn't come with more knockouts. It's a wylex, and it had 2 20mm on the bottom and a much bigger one - about 40mm maybe, on the top.

My armour comes in one of the bottom holes and i wanted a 20mm on the top for conduit. Now i have one.

thanks

slip

should have got a 20mm with ease

 

[slippyr4]

yeah, but i meant out of the ones i had in stock. my holesaws have all been bought for specific needs, evidentally i've never needed a 20 before.