Radiator pipework behind skirting?

[OvertonPlumber]

Dont bother with the cobalt drills you will be there for hours.

structural steel is made of poor quality steel very dense but comparatively soft.

What you need is a can of wd40 or cutting oil a new 25mm metal hss holesaw proper one that goes in a starret style holder.
A fairly oki drill my cordless 24volt bosch sds drill will do it.
start drilling and spray plenty of oil to keep it cool, maybe a rag below to avoid soaking ceiling. Structural lads always ask you to drill through the centre of the web (middle of joist) to avoid weakening the span.
My record for a 10mm steel is 2mins 5 secs with sds on, quieter in just drillmode though!!
drilling 25mm will allow use to use standard electrical grommets or you could sleeve it with a bit of 22mm hep.
i spent like 4 hours once drilling through steel with a conventional drill bit once.
mag cutters are ideal but not very portable

 

[TicklyT]

An often repeated error cutting steel is running the drill or holesaw too fast.

Steel like RSJs are made of cuts best at speeds between 60 and 100 feet per minute.
A 1" cutter has about a 3" curcumference,, so it sweeps about a foot in four turns. So you want to spin it at about 250 to 400 RPM.

Running the cutter too fast generates excessive heat, which can blunt the cutter and may locally harden the steel you are trying to cut at the same time.

Keep things well lubricated and cool, use a sharp tool at the right speed and steel cuts like butter.

 

[zand108]

I realise that this is slightly late. but I stumbled across this thread and realised I hadn't returned as promised to update on my experience. Thinking better late than never... Here goes

I did drill the joist & for the benefit of anyone else that might be interested here is what I used:

• A basic 18v Ryobi+ drill in Normal Mode (Not Hammer) (No SDS)
  1x Bi-Metal Arbor http://www.toolstation.com/shop/Pow...s/Holesaw+Arbor+Hex+14+30mm/d80/sd1530/p42954
  2x Bi-Metal 25mm Holesaws http://www.toolstation.com/shop/Pow...esaws/Bi+Metal+Holesaw+25mm/d80/sd1530/p56846
  1x Can Cutting\Tapping Fluid http://www.toolstation.com/shop/Aut...ing+Cooling+Lubricant+400ml/d60/sd2795/p75018

I went through the centre of the RSJ and I was surprised because drilling through the RSJ was tough but was nowhere near as difficult as I was expecting. I applied a bit of pressure behind the drill and didn't let it run too fast. I drilled through each hole in about 20mins, and it only took that long as I kept stopping every 5-10 secs to spray a shot of fluid over the drill bit and hole. Which meant putting the drill down to pick up the can. I did break several teeth off the first holesaw when it broke through to the other side of the RSJ as I was applying too much pressure and wasn't holding the drill straight. Finished by sleeving the pipe in 22mm Speedfit.

Simples!!

Many thanks once again to all that contributed.