Tool recommendation for cutting 25mm cable entry

[youngplug]

Hi, I have a job coming up in which I need to cut a new cable entry for a 25mm armoured gland in an existing consumer unit. There's plenty of space for it in an existing 3 phase protek board. But it's awkwardly situated and no precut knockouts available. Just wondering if any of you have any recommendations for the best tool for the job?

 

[pete01]

25mm cutter

Armeg SSH025 25 mm Sheet Steel Holesaw, Red : Amazon.co.uk: DIY & Tools

Free delivery and returns on all eligible orders. Shop Armeg SSH025 25 mm Sheet Steel Holesaw, Red.

www.amazon.co.uk

You can probably get one cheaper

 

[mattylad]

A lot will use a 25mm hole saw, these need to be used on a slow speed with plenty of pressure applied, go fast and you ruin the teeth.

One of these:

https://www.screwfix.com/p/starrett-a1-hex-shank-multi-material-arbor-with-80mm-pilot-drill/56120

And these:

https://www.screwfix.com/p/starrett-fch0100-multi-material-fast-cut-holesaw-25mm/1044p

Costly for a first and only use, but very handy for future use, you can get different sized saws to fit on the arbor, although there is a different arbor for the bigger sized saws.

Or you can use a stepped drill.
This type of thing:

3PCS HSS Step Bits, High Speed Steel Step Drill Bits Set - (4-12mm, 4-20mm and 4-32 mm) Cone Drill Bits Hole Cutter for Wood, Stainless Steel, Sheet Metal by SS SHOVAN : Amazon.co.uk: DIY & Tools

Free delivery and returns on all eligible orders. Shop 3PCS HSS Step Bits, High Speed Steel Step Drill Bits Set - (4-12mm, 4-20mm and 4-32 mm) Cone Drill Bits Hole Cutter for Wood, Stainless Steel, Sheet Metal by SS SHOVAN.

www.amazon.co.uk

Or you can use a 25mm Qmax punch, but again this is too costly for a single use.

Lots of options, get the stepped drill bit set (others available) from Amazon.

 

[mattylad]

Make sure you clean the paint off both sides surrounding the hole so the gland earths well, paint is not a good conductor.

 

[youngplug]

Thanks for you replies. In your opinion will these really do it? I bought one of these:
Mollom Heavy Duty Carbide Hole Saw
and tried it out this afternoon on the back of an old spare enclosure I've got at home, and even with a good pilot hole the drill bit broke and one of the teeth shatter on the hole saw (I really didn't give it that much either so I'm pretty disappointed in that and worried about being up the creek at the client's house).

Good shout matty. I'll make sure it's well earthed.

 

[pete01]

The one I posted will definitely work I use them most days take it easy, put something inside to catch the swarf, dont drill into any wires.

 

[youngplug]

Sound advice, thank you

 

[mattylad]

I would suggest returning the Amazon one, seems like it was garbage.

Although if you do wobble it the bit can break, you need a firm hand on the drill (preferably 2 hands).
Again, do not try and use speed, use slow cutting and above gentle force, some cutting paste/oil will also help (3in1 at a pinch).

 

[ericmark]

If the hole already exists as 20 mm, I use a cone cutter.