Step Drill Bits

Vitesse · Feb 11, 2016

I have a metal clad CU that I am currently installing, it's the MK Sentry one and I want to use the Wago Sprint glands on it. They make a Sprint gland that is 25mm and will accept 2 x 2.5mm T&E for a ring final. The problem is all the knockouts on the box are either 20mm or 32mm.

If I bought a step drill bit that will enlarge one of the 20mm holes to 25mm, will it do it cleanly and give me a nice clean cut enlarged hole? I have not used one before and I don't want to fork out nearly £40 if it just makes a mess of the CU casing. Also if it does what I want it to do, I guess it would be a good investment to add to the tool bag with Amd 3 CU's now required.

amlu · Feb 11, 2016

i have a cheapo set, 20 quid or something for a set of 3.
and they work very well. make sure you hold the box properly, dont go too fast and use plenty of drilling fluid.

Vitesse · Feb 12, 2016

amlu said:
i have a cheapo set, 20 quid or something for a set of 3.
and they work very well. make sure you hold the box properly, dont go too fast and use plenty of drilling fluid.

Thanks for that. It looks like Toolstation do one for £20 odd so a lot cheaper than the Screwfix one I was looking at.

davesparks · Feb 12, 2016

Use a 25mm hole saw just put a 20mm inside it on the arbor to use as a pilot. Or put a reducer into one of the 32mm holes

Barry White · Feb 12, 2016

Use a qmax cutter they work well and leave no burrs and much faster
Q.Max Sheet Metal Punch Hole Punch - 25.0 mm | eBay

Vitesse · Feb 12, 2016

mykey said:
Use a qmax cutter they work well and leave no burrs and much faster
Q.Max Sheet Metal Punch Hole Punch - 25.0 mm | eBay

I have a set of those from my classic car restoration days. Do you think that they will work ok despite the fact that the existing hole is 20mm, much bigger than the hole that you would normally drill to use them on sheet metal?

Barry White · Feb 12, 2016

Easy to test on a 2 gang back box knock out the 20mm in the rear and centralise the punch

davesparks · Feb 12, 2016

Vitesse said:
I have a set of those from my classic car restoration days. Do you think that they will work ok despite the fact that the existing hole is 20mm, much bigger than the hole that you would normally drill to use them on sheet metal?

Yes they work fine for it

Leesparkykent · Feb 12, 2016

https://www.sparksdirect.co.uk/Acce...Fastest-Way-to-Drill-Sheet-Steel#.Vr1_9ZFFCSE I find these work well. http://www.remora.net/catalogue/nyl...ts/GripLoc-Consumer-Unit-Flat-Form-Kits-Nylon I find these cheaper than the wiska equivalent.

sam400 · Feb 12, 2016

The wiska emt glands are spot on for bringing t&es thru a 20mm knockout. However if you want to make the knockout bigger the CK hole enlarging adapters are really good and only about £6

Vitesse · Feb 12, 2016

sam400 said:
The wiska emt glands are spot on for bringing t&es thru a 20mm knockout. However if you want to make the knockout bigger the CK hole enlarging adapters are really good and only about £6

Thanks Sam. Those Wiska EMT glands, I assume that the centre of them is a flexible membrane like the Wiska boxes, and you just punch a hole through them with the cable. Would you get 2 x 2.5mm T&E through a 20mm one for a ring final?

davesparks · Feb 12, 2016

Vitesse said:
Thanks Sam. Those Wiska EMT glands, I assume that the centre of them is a flexible membrane like the Wiska boxes, and you just punch a hole through them with the cable. Would you get 2 x 2.5mm T&E through a 20mm one for a ring final?

Nope, they're a stuffing gland with one or two oval holes instead of a round one.

Personally I don't see what the fuss is all about, a grommet or bush will do the job just as well.

sam400 · Feb 13, 2016

Vitesse said:
Thanks Sam. Those Wiska EMT glands, I assume that the centre of them is a flexible membrane like the Wiska boxes, and you just punch a hole through them with the cable. Would you get 2 x 2.5mm T&E through a 20mm one for a ring final?

yes exactly that, 2x 2.5s will fit fine. There fire retardant so in the spirit of 421.1.201!
cheapest I have found them is TLC at £3.60 for the assorted pack

Vitesse · Feb 13, 2016

Thanks Sam I will invest in some, sounds like the ideal solution.

davesparks · Feb 13, 2016

sam400 said:
yes exactly that, 2x 2.5s will fit fine. There fire retardant so in the spirit of 421.1.201!
cheapest I have found them is TLC at £3.60 for the assorted pack

Fire retardant is not in the spirit of the reg, non combustible is, there terms are quite different.

sam400 · Feb 13, 2016

davesparks said:
Fire retardant is not in the spirit of the reg, non combustible is, there terms are quite different.

The 960 deg flame retardant grommets that I suggested are more in the spirit of the reg than the standard grommets and bushes that you have just suggested. wouldnt you say?

shanky887614 · Feb 13, 2016

most step cutters will be fine, ive had mine for a year and it still works fine (ive used it on panels, unistrut and trunking etc)

if you do use a holesaw use a decent one as some don't last long

shanky887614 · Feb 13, 2016

sam400 said:
The 960 deg flame retardant grommets that I suggested are more in the spirit of the reg than the standard grommets and bushes that you have just suggested. wouldnt you say?

it doesnt need to be flame retardent the reg is about the enclosure.

i think a brass bush and lockring is better than a plastic stuffing gland.

sam400 · Feb 13, 2016

shanky887614 said:
it doesnt need to be flame retardent the reg is about the enclosure.

i think a brass bush and lockring is better than a plastic stuffing gland.

No it doesn't need to be flame retardant but it's not always about doing the bare minimum,

What IP rating is a 20mm bush with twin and earth going thru it?

shanky887614 · Feb 13, 2016

sam400 said:
No it doesn't need to be flame retardant but it's not always about doing the bare minimum,

What IP rating is a 20mm bush with twin and earth going thru it?

depends how many twins are going through it

sam400 · Feb 13, 2016

shanky887614 said:
depends how many twins are going through it

OP says ring final is being connected so let's say 2

shanky887614 · Feb 13, 2016

sam400 said:
OP says ring final is being connected so let's say 2

i would use a trunking header rather than stuffer or whatever for each cable/circuit so its irrelevant what the ip rating of the trunking is.

i wouldn't install cables clipped direct except as a last resort, id rather have a length of mini trunking upto the board than clipped direct

sam400 · Feb 13, 2016

shanky887614 said:
i would use a trunking header rather than stuffer or whatever for each cable/circuit so its irrelevant what the ip rating of the trunking is.

i wouldn't install cables clipped direct except as a last resort, id rather have a length of mini trunking upto the board than clipped direct

I also use a trunking header on CUs where possible. I did a CU this week where all the cables were rear entry apart from one that was clipped down the wall above the board. I used a wiska emt grommet to bring this circuit thru the top surface off the board.
A neat and compliant solution that cost me about 30p

Skimpy Wan · Feb 14, 2016

Just had a look at the GripLoc® Consumer Unit Flat Form Kits and I can't see how they differ from a 20 / 25mm CTS gland?

I used these for drilling conduit, patresses, consumer units etc and they seems to last well (still on 1st set, but I use cutting compound when used on metal).

Am-Tech Large High Speed Steel Step Drill Set (3 Pieces) from Amazon.

From memory 2 x 2.5mm 6242Y cables will fit in a 14-16mm whole in plastic CU, patresses etc and 16mm with grommet strip in a metal CU.

telectrix · Feb 14, 2016

what kind of gland would you use for these twins?

[ElectriciansForums.net] Step Drill Bits

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