Boyo, as an electrician I machine bend pipe all the time. It requires basic geometry,and some trial work to establish radias take up and gain.Those inexpensive benders may work or they may wrinkle the pipe depending on the bender design and ductility of the steel, they are generally designed for crude bending.I have seen muffler shops do a terrible job, crushed pipe on the bends etc.To made a proper 30-90 degree bend on thin wall pipe,the bender must have a bending shoe and a follower , both of which have rounded sides to prevent the pipe from distorting.Most of these benders are for heavy wall pipe ,schedule 40, which need no additional support. Check the machine out closely before buying.
