Pivot point produces a perfect radius
Mark the centerpoint of the radius on your workpiece. Sandwich the workpiece between a square pivot board and the bandsaw's blade so the centerpoint rests flush with both the blade's leading edge and the edge of the pivot board.
To cut a perfect radius, simply turn on your bandsaw and, careful to keep the pivot mark in contact with the corner of the pivot board, rotate the workpiece until it rests on the pivot board's adjacent edge.
—Serge Duclos, Delson, Que.