Curved Corners in Concrete
If you need to build a form for a concrete step and you want a tight radius on the front corners, you could get a piece of tempered hardboard and try to bend it to the right radius, but there’s a better way.
Robert Harrington of Milford, CT had to be a concrete step with front corners that had a 6 inch radius. That meant that his usual trick of using tempered hardboard to form that radius wasn’t going to work. He realized that he could use a 12 inch cardboard form. The first thing he did was cut it to the same length as the form boards, and then he cut it into four equal segments. Once he did that, he took a piece of 1×4 (the same height as form boards), and attached them on either side of the curved segments. The curved assemblies are then screwed to the form boards, and the entire form is ready to be staked in place and filled with concrete.