It will be more difficult to dock round pipes at any angles than profile ones. On a round surface, do not make an even marking with a square. Therefore, you have to resort to programs from the Internet to download the desired template from paper (if you have a printer).
Or you need to use an assembly saw, again, not everyone has one. Therefore, I want to share my method of such joining with garage self-taught in welding and plumbing. There is nothing complicated in it, no calculations and calculations. So, let's begin.
I took two pipes with a diameter of 42 mm. I put them to each other at an arbitrary angle, while the ends of the pipes should touch. I fixed (limited) this angle with the help of two pieces of channels, so that after cutting off unnecessary parts of the pipe, I put them back into this given angle - inside the corner from the channels.
It is necessary that the pipes that we join were exactly cut off at 90 degrees. By the way, recently on the channel there was an article on how and how to quickly mark a round pipe for cutting at 90 degrees, be sure to read-a useful device-article HERE
Now you need to measure this distance, where the extension of the pipe (supposedly) should converge at one point. We throw this size from the middle (in height) of the pipes.
I take two rulers, you can attach one ruler, and replace the second with any thing, the main thing is that it should be like a continuation of the outer wall of the pipe. I measured it and it turned out to be 60 mm.
Marked the desired size of 60 mm on both pipes. We throw the size from the end of the pipe. Let me remind you that I do not know what the desired degree in our joint is, this is done in fact, exactly at the degree that is needed for our purposes.
Now you need a half of a disc from a grinder, I think in the garage the techies always have an unnecessary disc-defective, painted, which has a strong beating. Here we break this disk in half. The disc is thin and perfectly grips a prominent mark on the metal.
You will also need a piece of a profile pipe or a piece of a corner. When marking, we put a professional pipe on both round ones so that it is at the same height.
We adjust the professional pipe, look from above so that it is exactly above the marks and above the end of the round pipe. We press the disc to the shelf of the professional pipe, check that the disc goes along the marks, and in this position we grumble the mark. We turn the pipe over and snag on the other side.
The disc mark is clearly visible to metal. But it is better to duplicate this mark with a pencil or marker. That's it, the markings are ready, now I will take a small grinder with a 125 disc and cut along the mark.
Everything, the joint is ready. I deliberately did not modify it with a grinding disc to a perfect fit. I just wanted to show this simple principle of how to join a round pipe without a cutting saw and complex calculations with templates. A primitive garage way!