Milling a rainwater channel in granite?

[Izze]

Hi!
I have built a granite staircase that I am very pleased with.
However, I missed installing a rainwater channel between the stairs and a landing (also in granite).
Thus, rainwater flows into the stairs unnecessarily. It's both dirty water and, of course, it freezes into ice when it gets cold, creating a lot of unnecessary ice.
I then found that there are stone cutters like this one https://www.flex-tools.com/en/products/lst-1503-vr-2-1/
I was thinking of milling a 4-5cm wide, maybe 0.5cm deep channel.
Does anyone have experience with similar work and any potential experiences?
Where could one rent such a machine in the Stockholm area?

Thanks in advance!

 

[GoC]

You should naturally have installed heating coils in the stairs. They melt both snow and ice.
Even with a water channel, it will likely freeze into ice.

 

[Andreas_kalmar]

What you are looking for is called a spårfräs and it can be found at Cramo, among others. I don't know where you live, but they are probably available almost everywhere.

 

[Derbyboy]

Well... it rather sounds like a job for a power saw or a regular angle grinder with a diamond disc.

Since you don't need to cut so deeply, an angle grinder and diamond disc from, for example, biltema, will probably suffice.

 

[Derbyboy]

If you have a picture of how it looks, I can quickly determine what you need.

I've spent most of the summer tracing granite, as part of a larger drainage project.

 

[Andreas_kalmar]

@Derbyboy difficult to run 2-3 parallel tracks with an angle grinder then run a groove cutter against a rail looks nicer I think

 

[Izze]

Do you have a picture of how it looks so I can quickly determine what you need?

I've spent most of the summer tracking in granite, as part of a larger drainage project.

Hi Derbyboy, thanks for the feedback and see the attached photo. Is it okay?
I was thinking of the channel roughly at the black line.
Isn't it a bit difficult to get an even depth and surface with an angle grinder?

 

[Izze]

You should have naturally installed heating coils in the stairs. It melts both snow and ice. Even with a water channel, it will still freeze into ice.

Yes, I have heating... but I'm trying to divert as much water as possible so I can turn off the heating as soon as possible and save a few kWh

Of course, there was a bit of incorrect construction, and in the photo below you can see how the water runs from the landing. The stairs are actually already dry, and I wouldn't have needed to heat them any more...if the water from the landing hadn't run over.

 

[Derbyboy]

I really don't know if I would have attempted to mill a groove there, partly because you won't be able to reach the corner (at the step) and partly because whether you use an angle grinder or a channel cutter, you'll still need to chip away the middle section (e.g., when using a channel cutter).

I've only used a channel cutter on concrete; admittedly, it was that horribly hard concrete, but granite is harder, much harder.

If you find a channel cutter with discs for granite, then maybe...

When I worked on granite, like real granite (rock), I found the angle grinder to be very compliant, made straight, fine cuts and it wasn't difficult to adjust the depth.

Can't you pry off the slab and take it to a stonemason...

 

[jonaserik]

Doesn't it get a bit difficult to achieve even depth and surface with an angle grinder?

You should rig with angle iron (45 degrees) and boards (for the depth) so you have something to follow, it should only be half a centimeter deep, maybe a bit difficult to keep the pieces in place, but perseverance prevails, and you might have difficulty against the step, maybe go a little on the side of it.

 

[Izze]

@Derbyboy difficult to run 2-3 parallel lines with an angle grinder, then using a wall chaser against a rail looks nicer to me

Thanks for the feedback and also found wall chasers with multiple blades like this one, then you should avoid having to chisel away the "middle piece"
https://images-na.ssl-images-amazon.com/images/I/71LSvn+8wzL._SX425_.jpg

One of the problems is probably what Derbyboy is getting at, how to manage it at the step.

 

[Izze]

You can't bend away the disc and take it to a stone mason....

I wish it were possible, but it's probably stuck very tightly with adhesive for stone....

 

[Derbyboy]

Thanks for the feedback and I also found slot cutters with several blades like this one, that should save you from having to chip away the "middle piece".

You will get several "middle pieces" with that machine too. To avoid middle pieces, you need to mill with an end mill or equivalent.

The advantage of such a slot cutter is that the groove automatically becomes straight and exactly the same depth.