Exposed curved steel often requires minimal or no ovality for aesthetic reasons. Customers installing stainless steel curved handrails for stairs want the pipe or tube to completely keep its shape whether the piece is straight or curved. This sometimes poses a challenge depending on the required material.
A CMRP customer sent prints for a complete handrail design for a high-end set of stair stringers. The material for the handrails required 1.5 inch 316 pre-polished stainless steel tube, with only a 1/16” wall thickness. Drawings showed three curved parts to three different radiuses. 3.5 inch ,9 inch and 26 inch radius inside.Working with the customer, we initially decided to roll the stainless handrails on a pyramid roll machine. This would be faster and a more cost-effective way to provide the customer with enough curved material to fabricate the handrails.
However, after rolling the first piece, it had more ovality than the customer desired. The wall thickness – 1/16” – was too thin for the required radii and there was distortion of about 1/8” In diameter. This ovality was too high considering that the handrails were exposed. After reviewing the drawings again, CMRP worked with the customer to change the design and rolling process in order to achieve the desired aesthesis of the handrails.
Using rotary bending machines with a mandrel, tubes were bent with straight tangents on both ends. This bending procedure helped keep the roundness of the tubes while being bent to incredibly tight degree tolerances. This time ovality in the curved sections was minimal.
With exposed curved or bent steel, it is particularly important to be flexible with the project design and material. Value engineering and consulting can help customer achieve the design they are looking for.