[John B]

Hi Valentin, some suggestions.

Bonding machine, Jim Crow, flypress, or when you are texturing the bar straighten it as you go.

Bonding machines, are used to produce iron tyres for wooden wheels, (now known as ring rollers they can be purchased as a modern powered machine) they are a mini version of levelling rollers as used in steel mills for levelling/straightening bars as they come from the strip mills. Ideal for hollow sections as it is easily controlled pressure that should not collapse the tube as it may do if direct pressure is applied to a point.

Jim Crow (Don't know why they are called that, but no doubt someone on the site will) come in various sizes and were used for straightening bars up to railway line size. You could adapt this frame configuration and mount an eccentric roller on a lever where the screw is shown to reduce the time taken to apply the screw principle.

Fly press, one of the best versatile tools for the workshop, depending on how badly the bars are bent, two bits of curved top handrail section, one at each side, and another piece mounted on a top tool, should prevent the textured finishes getting marred. Just feed it through and press it level.

Finally, if you are texturing a bar, can't you just keep it straight as you are going along its length?