# Drilling Holes in Van Roof (Metal)



## caulkhead

Morning All,

I need to drill two holes in the roof of my Renault Master van for the two separate cables from a twin-lens camera. The holes need to be approx (havn't measured yet) 3/4 " in order to accomodate the rubber grommets, so quite big holes! I have found advice on here about drilling into GRP but cannot find any advice re:metal. I found several articles on line saying that drilling into thin metal can be difficult and result in a hole the shape of a 50 pence piece!

Has anyone done this? Has anyone any advice on how to get a perfectly round hole of the size mentioned.

Caulkhead


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## 113016

Hi Caulkhead.
I have never had any problem drilling holes in GRP or metal, no matter what size, even 4 inches.
I do use quality hole saws, if you do similar, I am sure it will be OK.
Maybe if you are worried, you could glue a wooden block to the inside, although, personally, I wouldn't bother!
It's just a matter of having confidence!


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## Zebedee

Hi Caulkhead

Use a hole saw - a decent one, rather than those cheap multi bladed jobs you can get in Halfords.

*NOT* this sort >>> NO <<<

One like this >>> YES <<<

Go very, very slowly and gently, and with your drill set at its lowest speed. I might even get a speed reducer for the drill. Only a few quid and cheaper than getting the roof fixed. The centre drill (Arbor) will ensure the saw doesn't wander, and you will get a nice clean hole.

Using these precautions it's not that difficult, but have a clean pair of underpants at the ready!! :lol: :lol:

Dave


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## listerdiesel

*Gre*

Or find somebody local with a set of hydraulic metal punches, the Greenlee type are what we use, but you do need room one side or the other for the hydraulic punch cylinder.

If you want to drill a hole, use the bi-metal hole saws, Bosch (white ones) are amongst the best, and get a saw that's the right size to start with. We've got a box of assorted sizes up to 95mm that we use.










You're too far away from us, otherwise you could have come to the factory and done it here.

Peter


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## EJB

When drilling (cutting) a hole for a new aerial, fibreglass not metal, I cut the outside first....just enough to the fibreglass depth.
Then the inside to the plywood depth.
Embedded in the insulation were a number of electric cables!

I was lucky....or perhaps not as I had done my homework and seen the danger mentioned on the net! :wink:

PS. I use the cheap 'NO' version above :roll:


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## cronkle

I would follow the advice already given about equipment.

I set the drill clutch to the lightest I can get away with and apply the gentlest pressure to the drill as possible. That way if the drill does bind then there is minimal tearing to the edges of the cut. I also vary the speed of the drill according to the 'feel' of the cutting action although too fast does give you less reaction time should things go haywire.


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## Zebedee

Good advice about the cables Ted. I didn't think to mention that.  

The "NO" version would be OK for fibreglass or wood, but I'd be a bit nervous about using it on aluminium. It can bind and tear very suddenly. Those multi blade jobbies are not very rigid, and the teeth are too vicious for slow cutting of metal.

In my opinion! :wink: 

Dave


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## 113016

Caulkhead, looking at where you live, have you any boatbuilding contacts? If so, I am sure that they would have a quality holesaw and would be happy to drill the hole for you.
The top tip, is NEVER buy cheap tools :!: they don't last 

edit.
I have just been looking at my hole saws, I must have about 30 of all sizes, up to 4 inches. Two small inner bosses and two large with twin, screw out locking pins.
They must be worth a fortune, as they are serious quality, and USA made


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## dalspa

I would pencil the 3/4" circle (use template), centre punch the middle and then drill out starting with a small drill and then larger drill bits. If biggest drill size is 1/2" then the metal should be easy to file out to the pencil line. For rubber grommets, the hole doesn't have to be exactly round. Make sure, before you start that there are no cables (as already said) or stiffening ribs behind.

DavidL


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## HarryTheHymer

If you are having to drill into the metal roof, I would be more worried about future water ingress. 

A neater solution would be to purchase a purpose made double entry junction box as used to take a cable from a satellite dish through the roof. These have cable glands which are waterproof.

Using this method you would only need to drill one big hole to take both cables through the roof and it wouldn't matter if you made a mess of the hole because it would be covered by the junction box. 

The junction box would need to be mounted on a bed of mastic to make it waterproof. When I say "junction box" it is actually a small cast alloy L-shaped unit which takes the cable in through the end and feeds it though 90 degrees into the van. 

I can't find a link to this item but perhaps others will know.


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## daffodil

caulkhead said:


> Morning All,
> 
> I need to drill two holes in the roof of my Renault Master van for the two separate cables from a twin-lens camera. The holes need to be approx (havn't measured yet) 3/4 " in order to accomodate the rubber grommets, so quite big holes! I have found advice on here about drilling into GRP but cannot find any advice re:metal. I found several articles on line saying that drilling into thin metal can be difficult and result in a hole the shape of a 50 pence piece!
> 
> Has anyone done this? Has anyone any advice on how to get a perfectly round hole of the size mentioned.
> 
> Caulkhead


I would heed the advice about getting a boat yard to do it for you ,just for peace of mind ,you never know they might even have a better solution ,after all they are experts and it has to be worth a drink to get it right 
Good luck whatever you decide


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## 113016

I drilled and fitted four of these through the aluminium sides.


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## caulkhead

Thank you to all who have replied with your excellent advice! This is what makes MHF such a great forum. 

I will update this thread when the job is done.

Caulkhead


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## EJB

Zebedee said:


> Good advice about the cables Ted. I didn't think to mention that.
> 
> The "NO" version would be OK for fibreglass or wood, but I'd be a bit nervous about using it on aluminium. It can bind and tear very suddenly. Those multi blade jobbies are not very rigid, and the teeth are too vicious for slow cutting of metal.
> 
> In my opinion! :wink:
> 
> Dave


Good comment Dave.
I used to drill lots of holes in glass so had the knack!
The 'Yes' one is certainly recommended :wink:


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## HarryTheHymer

HarryTheHymer said:


> If you are having to drill into the metal roof, I would be more worried about future water ingress.
> 
> A neater solution would be to purchase a purpose made double entry junction box as used to take a cable from a satellite dish through the roof. These have cable glands which are waterproof.


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Marcle Leisure do a 2 cable plastic waterproof junction box suitable for mounting on the roof. I believe it accepts cable diameters from 2mm to 6mm (outside diameter). See link below:

http://www.marcleleisure.co.uk/stor...sid=791caf6f495d58bebfb1cc6ffcaf8c6f&x=36&y=9


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## nicholsong

caulkhead said:


> Morning All,
> 
> I need to drill two holes in the roof of my Renault Master van for the two separate cables from a twin-lens camera. The holes need to be approx (havn't measured yet) 3/4 " in order to accomodate the rubber grommets, so quite big holes! I have found advice on here about drilling into GRP but cannot find any advice re:metal. I found several articles on line saying that drilling into thin metal can be difficult and result in a hole the shape of a 50 pence piece!
> 
> Has anyone done this? Has anyone any advice on how to get a perfectly round hole of the size mentioned.
> 
> Caulkhead


To avoid problems with water ingress could you drill the holes through the side of the van or above the rear doors? - that way the rain runs down away from the holes/grommets/junction boxes, whatever you use.

Obviously depends on inside routeing of the cables.

Geoff


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## bigtree

I would definitely go for the twin entry roof box sikaflexed to make sure of no leaks.


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## caulkhead

> Geoff said:-To avoid problems with water ingress could you drill the holes through the side of the van or above the rear doors? - that way the rain runs down away from the holes/grommets/junction boxes, whatever you use


Unfortunately the doors are full height so the camera has to go on the roof and running the cables to the side of the van would leave too much cable flapping about, but thanks for the suggestion Geoff.

Caulkhead


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## BillCreer

bigtree said:


> I would definitely go for the twin entry roof box sikaflexed to make sure of no leaks.


Drill 2 holes close together just over cable size, thread the cables, seal around them with sealant then stick one of the above boxes over them.

Make sure to get all your cables threaded and correct lengths as you only get one chance.


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## powerplus

hi 
i would not use grommets on the roof

i would prefer something that would hold the cable tight and be waterproof

barry


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