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?

 

[westward10]

Certain enclosures need considerable force to get the knockout out but I have never used Fusebox so can't comment. Have you used Fusebox before?

 

[Flanders]

Clamping a peace of wood inside. Before drilling may help prevent dislodging the knockout . I have not use fuse box so dont know how secure the knockouts are.

 

[SJD]

I've tried in the past with Fusebox, the knockouts came loose I'd either use a gland reducer, or put several cables in a larger size gland. Not much help if you want to gland a number of SWA cables, then perhaps fit a metal plate over the holes with the holes you want drilled or cut.

 

[ppelec100]

Certain enclosures need considerable force to get the knockout out but I have never used Fusebox so can't comment. Have you used Fusebox before?

I have used fusebox before but I’ve never had to drill the knockouts, whenever I’ve needed to drill them it would be on a surface with a plain section

 

[ppelec100]

I've tried in the past with Fusebox, the knockouts came loose I'd either use a gland reducer, or put several cables in a larger size gland. Not much help if you want to gland a number of SWA cables, then perhaps fit a metal plate over the holes with the holes you want drilled or cut.

Ahh that’s kind of annoying to hear, I’ve got what looks like 3 x 20mm swa and a 20mm flexi conduit gland to fit on the top surface.
I don’t understand why they would put such big knockouts with such ridiculous spacing.

With the metal plates, what did you use that’s convenient and won’t look so bad?

 

[nicebutdim]

I've tried in the past with Fusebox, the knockouts came loose I'd either use a gland reducer, or put several cables in a larger size gland. Not much help if you want to gland a number of SWA cables, then perhaps fit a metal plate over the holes with the holes you want drilled or cut.

I've drilled one Fusebox enclosure - think they have a 32mm knockout on the side and I needed to get a 25mm SWA gland in pretty much that very spot. Partially drilled the knockout with smooth cutting holesaw and had no issues (despite concerns to the contrary). This was a while back, but fairly certain there was a 32mm knockout on the left side of their 4 way mainswitch enclosure.

 

[SJD]

The only time I've used a metal plate, it was to line up holes with metal conduits in a service cupboard outside a flat, and didn't care what it looked like within reason.

More recently when I needed holes to align with some pyro glands and look ok I cut a set of new holes further forward than the knockouts.

I seem to recall older Fusebox units had smaller holes, but the last 2 or 3 years they got larger.

 

[SJD]

It occurs to me you could bolt a metal plate inside the box under the holes you want to partially drill then all you see is a few bolt heads.

 

[Mikegh]

You could fit a different CU for this job

 

[Flanders]

Another option might be it fit trunking along the top.

 

[Mikegh]

Another option might be it fit trunking along the top.

A new house

 

[pc1966]

I would be weary of fixing anything heavy/stiff to a knockout in case it breaks off later. For SWA you ought to have a CPC tail to a banjo or earthing nut anyway, but it still leaves the mechanical vulnerability.

A metal plate inside is an obvious solution, you could even have it fixed partly by the other 20mm fittings if glands are used and not grommets, etc, but you would only need a couple of short screws and nuts (ideally nylock or similar so they stay in place and don't loosen with vibration or thermal cycling).

Also @Flanders suggestion of some trunking is a good idea if you need a selection of cables, etc, and they are not suited to the standard layout. You can put a couple holes between them and some short 20mm or 25mm bushes and lock nuts for both cable protection and mechanical/electrical fixing of the trunking to the CU box.

A hole punch is really hand here as you can mark and pilot drill your hole locations, then G-clamp the CU & trunking together (or screw both to the wall as planned), and offer the male half of the punch to an existing knockout hole and place the female half on the trunking side, tighten the pulling bolt et voilà! a neat hole perfectly aligned for your bush to pass through. Repeat as needed...

 

[SparkySy]

I have done this using a galv conduit box lid on the underside of the hole. Knock out the original 32mm hole then fix the box lid in position with 2 m4 bolts and drill the size you require.
In some cases where I needed a bit more strength I have drilled an extra 2 fixing holes in the box lid and board.

 

[UNG]

A Q-Max cutter is useful for this sort of job as you only need to drill a 6 or 8mm hole for the bolt so it limits the stress on the knockout that a holesaw or step drill creates

 

[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

Greenlee 50600770 12.7mm x 11.9mm "D" Shaped Punch available for speedy global delivery. We sell a wide range of hole punches at low prices.

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