Greetings,
Does anyone have some good tips on cutting a clean hole in metal roofing? The roof is a 10-12 pitch with 1/2" foam underneath and pole building style framing- meaning there is no OSB underneath, just 2x4s every 2'. I'd like to use my hole saw, but know that it will be difficult or impossible to make a clean and plumb roof penetration on the steep pitch, since the cut will be angled and start on just a small section of the eventual hole and nothing will hold the drill/saw firmly.

my only thought was to start the hole in one of the 2x4s. despite having the same issue cutting the wood at an angle, I'm guessing the wood will be easier to start, and making a clean start there is not important. This way, the hole saw has a firm guide by the time it gets to the metal, and perhaps will make a clean, oval shaped hole, without wobbling all over the place.

I would appreciate any tips from someone who has some experience with this. I really want to make a clean hole in the metal so it is easy to seal between roof and vent pipe (as added protection besides the rubber boot).

either:


jig saw and oval template

or

roofer

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Template....Die Grinder or Drill....Tin Snips

Use a long 1/4" drill bit in place of the hole saw's pilot bit. That will hold it centered while you start the hole and most of the way through the metal.

That's the way I do it, a long pilot in a bimetal hole saw, it gives a nice oblong hole on a steep roof.

I make my first hole (hole saw) square with the roof angle so the teeth are all contacting the metal above and wood underneath. Once that is made, I'll begin to bring my drill up incrementally in small 'bites' until I have a vertical cut made. Last, I'll oval the hole out.