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?

 

[pc1966]

Agree with the Q-max hole punches, though there are better places to buy them than Amazon, for example:

Q Max Sheet Metal Hole Punch Metric | Hole Punches

Buy Q Max Sheet Metal Hole Punch Metric and other Q Max Hole Punches at Tooled-Up.com. Fast Delivery.

www.tooled-up.com

Q-MAX Cutter Round - Metric

Q-MAX Cutter Round - MetricQ-Max Cutter for manually punching holes in sheet steel up to 1.6mm and aluminium up to 2.0mm. Very simple 100% British made tool that has been in production for over 50 years. To use, you simp

stakesys.co.uk

https://www.sjtools.co.uk/punches/q-max-sheet-metal-punch-metric/

I have a few of them and they are really useful for this sort of a job (though the like of the Armeg hole saws are nice as well for 16/20/25/32mm). A big advantage is little in the way of swarf, and the ability in this sort of case to punch one sheet (or use pre-punched holes), clamp together, and then use the 1st hole as an alignment for the 2nd hole to be punched.

You can also get non-round hole punches for various things like D-connectors, etc, but they are much more expensive!

 

[pc1966]

For the curious among you, here is an example hole punch for a BNC connector with the anti-rotation flat:

Greenlee 50600770 12.7mm x 11.9mm "D" Shaped Punch

www.heamar.co.uk

And here is an example for a computer D connector:

50124730 | Greenlee Punch and Die Tool, 41.9 x 11.3mm, 25 Way D R, Hydraulic Operation | RS

uk.rs-online.com

Be warned about the D connector punches as each size (like 25-way) has up to 4 punch options: for front or rear mounting on the panel and sometimes for M & F options. It becomes expensive to collect them

 

[ppelec100]

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?

 

[pirate]

I agree that the Q-max punches are great for such hole cutting. There's no jarring and vibration like with a holesaw and no chance of breaking through and damaging already installed gear. Been there, done it...but sadly didn't get the T-shirt!

 

[pc1966]

The 32-20mm reducer (RE3220G) looks like a really handy thing to keep in the 'misc' box of bits just in case, I guess along with a couple of others (such as RE2520G and RE3225G) for situations when you need to fit SWA glands or similar to the wrong size of punch-out. Or someone just drilled the wrong size...cough...

 

[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