Bending Stainless Steel Tubes for Circular Stair Handrails


Questions about surface finish often arise when there is a requirement for bending stainless tubes for circular stair handrails.  Will the helical tube bending process damage the finish?  And what if the project requires bending polished stainless tubing?  What if the tubing was polished before it was rolled helically?  What will it look like?

A recent requirement called for type 304 stainless tube with a 1 ½” outside diameter, a 3/16 wall thickness, and a #4 finish. The customer needed it curved helically to a 16ft inside radius with a 32 deg pitch.

The customer was told that there could be scratches and swirl marks on the face of the tube; scuffs and possible carbon impregnation on the outside  of the tube; and possible shipping damage caused by the freight company. The customer appreciated this information and said that he will put in extra fabrication time to touch up or buff out the possible markings. He also mentioned that most polishing tools are easy to use on straight material.  And if he were to get pre-polished material and curve it, it would still be a lot easier to fix any imperfections rather than try to polish the tube in the curved stage.

Here are some of the different finishes:

#4 finish is a directional grained finish created by polishing to the equivalent of 150 grit abrasive.

#6 finish is a directional grained finish created by polishing to the equivalent of 240 grit abrasive.

#7 finish is a buffed finish and is mirror like but has some surface imperfections.

#8 finish is mirror-like and has had all surface imperfections removed resulting in a very smooth and reflective finish.

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