Hollow steel tube can be challenging to bend without making it buckle and crimp. Smiths have developed a variety of techniques and equipment to solve the problem. One simple solution is to “trick” the tube into acting like a solid by filling it with sand. With this method, you can make a tight bend or even scroll the tube–all without purchasing any additional equipment or spending lots of money on materials.
Cut the square tube steel at least 1 foot longer than the piece needs to be.
Weld a small piece of plate on one end to cap the tube.
Fill the square tube steel with sand from the open end, making sure that the sand is well packed..
Weld the cap on the open end of the tube. You now have a square tube steel bar that will behave like solid steel.
Heat only the area that you want to bend until it is bright yellow. Avoid heating any part of the steel besides the area that needs to be bent.
Bend the bar in the shape that you want using a vice or jig. As soon as the bar becomes red, stop and reheat it.
Cut the caps off and drain the sand.