cutting angles:

The correct way is with a 24" abrasive saw and an appropriately angled block to put between the pipe and the saw's fixed jaw.

Pipefitters working on heavier pipe in a shop would use a large bandsaw. In the field they would carefully lay out the line and cut it with a torch.

If a large saw isn't available you can lay out the line and use a plasma cutter freehand to make the cut. If the tube wall is thin you could cut slightly proud of the line and then sand to the line.

Grant

Dremel tool or other rotary cut off tool with a fiber reinforced thin wheel. $30 at Wally World

Cutting is the easy part. Having the line to cut is the hard part. In my high school drafting class I learned how to layout a piece of paper with the line on it. Cut out the paper and wrap around the pipe. trace line and you're good to go.

I searched the web for instructions on this. its easy but a bit more than I can explain. I cam across this layout software that will give you one free sample:

Karl

Normally there is a moving joint section that is used for that.

Cutting is an option - if you get the angle correct. Remember you have to crimp the top end to insert and it needs to be long enough.

I had a middle sized wood stove and a 16' single wall tube to the roof box. The air conditioner / fan unit for central air input or return air was just at the top of the wall behind the tube. We could heat the whole house and then shut off the fan - once the house was warm.

Martin

Mart> sal wrote:

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OK, step by step.

1.Get 2 long pieces of wood, join them at 90 degrees (nails are fine.) 2.With a protractor, mark off an included angle of 22 degrees on the (imagined) vertical axis. (You are building a triangle) 3.Get another piece of wood, lay it across the created 22 degrees,check alignment where it cross the bottom bit of wood, should be 68 degrees, (non of this is super critical) 4.Lay pipe along created top of triangle - hopefully you've made this rough as so that the vertical bit goes past the pipe where it lines up with the edge. 5.Bang some sort of support on the triangle, nearby tree trunk, whatever, to stop horizontal movement of pipe on triangle..

1. With a marking pen, hold against pipe at the 22 degree angle point you have created, rotate pipe, you now have cut line.

7 Use a 4 inch angle grinder to do the cut - if you want to get fancy, and your angle grinder supports it via an arbor, use a thin cutoff blade. Otherwise, hack/burn your way through with a standard angle grinder cutting blade...

Now, hope you can follow all that - my written English aint too hot. If you like, email me off list and I will send you a sketch.

Andrew VK3BFA.

I've not seen that done. On anything I've done, it's the flashing HOLE that's adjusted, the stove pipe just goes straight through the roof vertically. And for sheetmetal vents like on driers and hot water heaters there are elbows with movable segments to get the desired angle by rotating one or more of them.

If it's just a stub for an attic vent, who cares if it's square or angled? You're not going to see it anyway and angling the bottom will make sticking some kind of cap and/or screen on there a lot more complicated than it needs to be. Unless you live where there's no cold weather and no bugs, you're going to need one or the other or both.

Stan

For what it's worth: a 4-12 roof is 18.4 deg from horizontal, not 22.

>

Thanks for the help guys, got it all figured out. My mistake 5-12 roof. The reason I am making my own vents is because dealers want 135.00$ +tax per unit, I need 4 and can make them a hell of a lot cheaper.

Sal

Nevermind how, I'm wondering..._why_would a vent pipe be cut on a bias? It doesn't mate to the roof surface, it pops up through it.