Step Drill Bits

[Vitesse]

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]

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]

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]

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]

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]

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]

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

 

[davesparks]

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]

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]

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]

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]

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]

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]

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

 

[davesparks]

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]

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]

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]

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]

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]

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