sal wrote:

Can someone explain how I can cut an 10 in. stovepipe with an 22% angle it
is for an vent pipe on an 4-12 roof .

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