This is a pipe bender with pipe size dies. If you bend something besides pipe with a pipe die, expect it to not work correctly. Mine makes a nice bend with the sch 40 pipe that it was designed for without using sand.
I get what your saying about the sand, but don't blame the bender because you used the wrong size tubing.
Also thinner wall will kink easier. I have a JD2 bender with a 1.750 die , 5.5" radius and if I bend 1.750 .093 wall (exhaust tube) with it it will have ripples in the bend. Bends 1.75 .120 wall perfectly though.
yes the jd2 bender is not made for thin wall tube.... if I remember right .095 is the thinnest the jd2 is made for.... I have had a couple jd2 benders now and love them to death!