A bender constructed as shown in the detail folio that comes with all our full plan sets. This system is quite capable of bending 100 mm x 12 mm flat bar as shown into a gentle curve. 

A similar bender. You will find it easier to control the bar twisting when the uprights are placed closer together

This semi professional bender that uses rollers with slots cut into them to stop any twisting of the flat bar. A standard hydraulic jack provides the power