A slip roll, manual or motorised, uses three rolls to form light gauge sheet metal into curves and pipe. The two front rolls of a slip roll are referred to as pinch rolls and they are used to feed the sheet metal into the rear, bending roll that places the arc in the sheet metal. There is either a handle that you manually use to turn the pinch rolls or a small electric motor that runs the pinch rolls for you.
Cut the piece of sheet metal to fit the width of the slip roll on the sheet metal shear. If you are making a round pipe, figure out the stretch-out of the sheet metal by multiplying the diameter of your pipe by 3.142 (pi) and cut that length as well.
Rest the cut piece of sheet metal on the bottom pinch roll and push the metal into the slip roll.
Turn the front knobs directly below the bottom pinch roll until the sheet metal is held tightly, or pinched, between the rolls.
Turn the pinch rolls counterclockwise to feed the sheet metal into the slip roll. Stop turning the pinch rolls when the sheet metal sits directly in front of the bending roll.
Adjust both knobs that move the bending roll until the bending roll is slightly higher than the sheet metal.
Run the sheet metal over the bending roll to arch the metal.
Flip the sheet metal and raise the bending roll slightly.
Run the sheet metal back through the slip roll to tighten the arch of the sheet metal.
Repeat the process of raising the bending roll and running the sheet metal through the slip roll until you achieve the desired arch on the sheet metal.