Abstract: A mandrel for bending a rectangular duct body is provided. A round part and a shaft pin hole are formed at the front end of the mandrel, connection pieces and rollers are formed at the front end of the mandrel, protruded parts for supporting the bent part of the rectangular duct body and depressed parts in which depression parts will be formed are formed on both sides of the rollers, and oil grooves are formed in the sides of the rollers. Accordingly, there is an advantage in that workability and productivity can be improved because frictional force between the rollers and between the inside of the rectangular duct body and the rollers is reduced when performing a bending work because grease within the oil grooves formed in the rollers performs a lubrication action.

Abstract: A multi-shaft bending machine for bending two rectangular duct bodies, such as trunk lead hanger arms for a vehicle at the same time. Barrier pieces are installed in a mandrel including three rollers and a rectangular duct body support that forms a bending machine so that two rectangular duct bodies are not mutually influenced when a bending work is performed on the two rectangular duct bodies. A rotation plate is rotated by a plurality of shafts connected to a driving motor through clutch gears. Accordingly, a difference between strain rates on the outer and inner sides of a bending part can be reduced, lubricating oil injected into the oil grooves of the rollers performs a lubrication action, and the structure of a bending machine can become simple because the rotation plate is rotated by the plurality of shafts connected to the driving motor through the clutch gears.

Abstract: A mandrel for bending a rectangular duct body is provided. A round part and a shaft pin hole are formed at the front end of the mandrel, connection pieces and rollers are formed at the front end of the mandrel, protruded parts for supporting the bent part of the rectangular duct body and depressed parts in which depression parts will be formed are formed on both sides of the rollers, and oil grooves are formed in the sides of the rollers. Accordingly, there is an advantage in that workability and productivity can be improved because frictional force between the rollers and between the inside of the rectangular duct body and the rollers is reduced when performing a bending work because grease within the oil grooves formed in the rollers performs a lubrication action.