Here's something to keep in mind for cutting any type of tubing, with any method (power saw, knife, hacksaw, etc.).
With any cutting tool/method, you can still get some rough edges at least, or some uneven lines at worst. If you accept that from the outset, and concentrate on how you are going to fix it after the cut, it will be easier and less stressful to make the actual cut. So how do you deal with it? Easy - make a simple flat sanding block by just adhering some sandpaper to a flat piece of plywood. Something a little larger than the diameter of your tubing. Then, use it to true up the edges after the cut. If you cut close, but not exactly perfect, it's a simple and quick matter to get it just right using this method.
I find this is actually faster, easier, and less stressful than trying to get an absolutely true and perfect cut with whatever saw I use. Plus it's cheap and requires no fancy tools.
But if you DO want to use fancy tools, the best way is to use a good 12" bench mounted disc sander. As long as your table and mitre guide are true, squaring up your freshly cut tubing is quick and comes out perfect every time. Works great with paper, phenolic, fibreglass, BlueTube, whatever.
For the record, I hand cut with a Japanese pull saw, and true with a 12" bench sander - with all materials. Most of the time the saw cut is about 98% perfect as is, and the sander finishes the job. But sometimes the power sander is not available, and in those cases the hand sanding method I described above works just fine.
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