Drilling holes in Fusebox knockouts?

[ppelec100]

I’ve always been alright with the knockouts provided for Fusebox consumer units but I’ve got a job coming up where I don’t want to use the large 32mm or 40mm knockouts.

I’ve got a 10 way board consumer unit to fit and the knockouts are so annoyingly spaced out, you could fit another 3 knockouts on the top if someone with common sense actually designed it.

I’ve never had to drill the knockouts and I want to know if I drill a 20mm hole centre of the 32mm knockout hole is the 32mm knockout going to drop out on me leaving me with a gaping hole I have to try and downsize or will I be okay if I drill it with low pressure and a sharp hole saw?

As they haven’t spaced it properly and I want to allow space for other knockouts in the future… what if I was to drill off centre so that my hole saw is cutting through the circular edge of the knockout will the knockout dropout?

 

[pirate]

I recently installed a number of new circuits in a building acquired by and adjacent to my local branch of the Men's Shed.
The CU was already in place, a new one installed by the landlord, simply providing lighting and sockets circuits. The added circuits were for the roller shutter doors, an additional lighting circuit, a hot water heater/handwash unit and an additional 4 socket radial. An electrician was engaged to connect all these to the CU. He was a very personable young man and did a very neat job. He was a bit concerned about drilling new entries into the board, but had his holesaw ready. I suggested he use a hole punch insted, and he confessed that he had never heard of such a device. I borrowed a 20mm from my pal who lives 5 minutes away, and the electrician was amazed at how easy it was to create the holes, with clean edges and no vibration. I leant him my Noga reamer to clean the new apertures, and he'd never seen one of these either.
I met him about a month later and he told me he had bought both of these tools. His employers refused to pay for them, but he was very happy to have them in his toolkit.
I guess we are talking about what car manufacturers used to call NVH...Noise, Vibration and Harshness.

 

[ppelec100]

I recently installed a number of new circuits in a building acquired by and adjacent to my local branch of the Men's Shed.
The CU was already in place, a new one installed by the landlord, simply providing lighting and sockets circuits. The added circuits were for the roller shutter doors, an additional lighting circuit, a hot water heater/handwash unit and an additional 4 socket radial. An electrician was engaged to connect all these to the CU. He was a very personable young man and did a very neat job. He was a bit concerned about drilling new entries into the board, but had his holesaw ready. I suggested he use a hole punch insted, and he confessed that he had never heard of such a device. I borrowed a 20mm from my pal who lives 5 minutes away, and the electrician was amazed at how easy it was to create the holes, with clean edges and no vibration. I leant him my Noga reamer to clean the new apertures, and he'd never seen one of these either.
I met him about a month later and he told me he had bought both of these tools. His employers refused to pay for them, but he was very happy to have them in his toolkit.
I guess we are talking about what car manufacturers used to call NVH...Noise, Vibration and Harshness.

I saw a video on one before but thought you needed a special Milwaukee tool to make the holes then you guys spoke about it again on this thread and so I searched again and I see you can make them by drilling a pilot hole and using Allen keys…

Are they that good? Do they wear out easily? What brands would you recommend?

 

[pc1966]

You can get expensive hydraulic and electric tools to apply the punching force, great if you do a lot of holes but very costly otherwise.

Most folks who only need to use a hole punch on an occasion just use the pulling bolts, some are Allen headed, others regular hex-head bolts. But make sure you keep the threads clean and lightly greased.

 

[Flanders]

Thanks for the tips guys,

I was thinking, I could use some 32mm to 20mm reducers to reduce the hole size and be able to use 20mm glands still without messing with the surface and structure etc

Something like this

https://www.cef.co.uk/catalogue/products/23838-32-to-20mm-reducer-galvanised-sold-in-1-s?gad_source=1&gclid=Cj0KCQjwiMmwBhDmARIsABeQ7xSDJaHncKYX7CFS_A8uEScnPvjprxWrz-VxZe9RY4ATVTa6VsrNr-EaAtTUEALw_wcB&gclsrc=aw.ds

If I can’t get hold of them, I’ll do what SJD has suggested and put a galv lid under the hole I want to drill and bolt it to the Cu

For future use… What consumer units do you guys usually fit that don’t have ridiculously big knockouts with ridiculously big spacings between them? Or which consumer units have no knockouts so you can drill your own?

We use hager design 30. Which have no knockouts at all but are more expensive.

 

[UNG]

Are they that good? Do they wear out easily? What brands would you recommend?

I doubt we would be recommending them if they were not up to the job