Cut holes in the building for DC lines?

[Rob Will]

I need to cut two perfect circles in the side of my pole barn for DC lines.

The cyclone inlet is 10" and the outlet is 12". I plan to install a sleeve made from PVC pipe couplers to isolate the DC pipe from the metal siding.

Any thoughts on how to cut two circles in the siding?

Rob

[Jamie Buxton]

One way is a router with a trammel arm. The trammel arm is an arm fastened to the router. At the non-router end there is a pin which sticks into a pilot hole you drill into the siding. A slightly less-tricky way is to draw a circle on the barn, hog the hole out with a saber saw or a sawsall, stick the duct through, and caulk the crack -- should be good enough a barn.

[Norman Hitt]

Rob, you don't say whether you are only going to be cutting through one layer of metal siding, or what, but to get a "clean cut" on the metal siding, (and whatever other sheathing there might be on the inside of the outer layer of metal), I would do the following;

Cut a piece of scrap plywood (5/8" or 3/4" thick), a little larger than the hole you want to cut, then from the inside of the siding, screw about three or 4 screws through washers and the metal siding into the plywood that is on the outside of the building to hold it tight against the metal siding. Place the screws an inch or more from the cut line of the circle. Next, drill a hole large enough for a hand held jigsaw's metal cutting blade, (jigsaw, not a sawzall). Drill the hole inside the cut line of the circle to give the blade a starting point, and then drill a hole in the center of the circle to insert a pin for the circle cutting guide, (trammel or whatever you want to call it) for the jigsaw, then use the jigsaw to cut the circle. This will hold the metal flat, keep it stabil and give the saw a solid base to run on throughout the cut. (If it wasn't clear, make the cut from the outside of the building, cutting through both the plywood AND the metal siding).

Note: If the plywood overlaps the ridges in the metal siding, (which I'm sure it will), place another piece of plywood between the Metal's ridges that will be thick enough fill the space between the metal siding and the outer plywood so the metal is held tight and flat for the cut.

I hope this makes sense.

[Rob Will]

Makes sense to me,
The siding is just one layer of metal so that will work fine.
Thanks
Rob