Some advice regarding 125mm hole for cooker hood fan please?

[HappyHippyDad]

Morning all..

I am about to quote for a cooker hood installation including core drilling for the vent. The fan is 125mm.

I have checked upon the sizes of core drill bits and 127mm is the closest fit. I cant see the 125mm ducting getting through that due to the outer diameter of the ducting being greater than 127mm. Does it fit through?

How much of an impact would it have on the motor if I used a 125mm-100mm reducer for the ducting?

Could I cut a 152mm hole and use a larger vent on the outside wall, also using a 150mm-125mm reducer for the ducting?

Cheers.

 

[Pete999]

Not really drill through from one side until the pilot shows and then drill through from the other side with the core drill engaged, rocket science is not required.

 

[egg67]

Think it's just the way you are shown How to do things , was always told to drill a pilot hole first then the biggy and go at it from both sides, but that was 34 years ago so things change with time, drill bits have got better and making good is just a bit of silicon

 

[Pete999]

Not really drill through from one side until the pilot shows and then drill through from the other side with the core drill engaged, rocket science is not required.

Think it's just the way you are shown How to do things , was always told to drill a pilot hole first then the biggy and go at it from both sides, but that was 34 years ago so things change with time, drill bits have got better and making good is just a bit of silicon

 

[Pete999]

Now you have to agree that's bull shyeet, not the vid your statement it's only a bit of silicone.

 

[egg67]

Think it's just the way you are shown How to do things , was always told to drill a pilot hole first then the biggy and go at it from both sides, but that was 34 years ago so things change with time, drill bits have got better and making good is just a bit of silicon

 

[jackhammerJIM]

If you do plan on drilling from either side make sure the pilot bit is the exact same size as the sds bit .

 

[marc8]

I've just measured some rigid 100mm ducting I have Murdoch, the outer diameter is 103-104mm. I'm pretty sure with ducting (unlike conduit) the specified size is for the inner hole, stand to be corrected though? Flexible ducting, although more malleable has an even bigger outer diameter relative to its inner diameter.

I also remember drilling a 107mm hole for 100mm rigid ducting and it 'just' scrapes through.

220 x 90 mm is approx 6"
204 x 60mm is approx 5"

 

[marc8]

Think it's just the way you are shown How to do things , was always told to drill a pilot hole first then the biggy and go at it from both sides, but that was 34 years ago so things change with time, drill bits have got better and making good is just a bit of silicon

lucky these days from what i have seen drill pilot hole, drill in 1" then club hammer, think it is in case they loose to many diamonds or is it too much time i am not sure maybe my age.

 

[egg67]

Silicon, sillycon or silicone it's all the same at the end of the day, just when I started out was drummed in to me that you do a good job as in Measure twice cut once, drill little them bigger, keep mess to a minimum and leave a good job

 

[NDG Elecs]

I think you are overthinking this a bit HHD. Core your ~105mm hole and use a 125-100mm reducer above the fan. It will work fine.

A good tip for hard engineering brick is to core through by around 25mm then stitch drill holes around the circle to speed up the remaining coring.

I sometimes core from both sides, depending on the finished surfaces inside and out. Does make it much harder to use rigid ducting though doing it that way. I tend to core from the outside to the inside, this due to the dust levels.

 

[HandySparks]

I tend to core from the outside to the inside, this due to the dust levels.

Could always get yourself one of these (and a hollow extension, if required):
http://www.screwfix.com/p/marcrist-dust-extraction-unit-150mm-3-pcs/4441F

 

[NDG Elecs]

Could always get yourself one of these (and a hollow extension, if required):
Marcrist Dust Extraction Unit 150mm 3 Pcs - http://www.screwfix.com/p/marcrist-dust-extraction-unit-150mm-3-pcs/4441F

Would be an excellent idea but I would need a vac too Handy!

 

[HappyHippyDad]

I've done both ways, ones okay for flexible ducting not for solid. Let the machine do the work, and don't be so impatient

I'm guessing drilling all the way from one side is better if using solid ducting?

 

[HappyHippyDad]

I shall be adding a FCU next to a kitchen socket then chasing perhaps 1.5m (no filling), fitting the cooker hood, core drilling and fitting ducting and outside vent.

I've estimated 4 hours but am thinking it may be closer to 5? Just trying to work out the quote!

 

[NDG Elecs]

I'm guessing drilling all the way from one side is better if using solid ducting?

Yeah defo. The actual shape of the core drill helps to keep the hole straight. If you core from both sides it is easy to deviate off from a nice straight line. Don't forget to angle it slightly to prevent water any water from coming in from the outside.

I think four hours sounds about right. 30-90mins on the core itself. 60-90mins chasing, fcu etc. Remainder for testing and tidying up.