a method of making circular and oval flanged rings , for the connection of thin walled circular and oval ducting , including circular and oval flanged rings having a sheet metal and air conditioning contractors national association standard t 24 profile . thin gauge lock form quality steel , from 10 to 20 gauge , is cut into strips with the strip ends butt welded forming flanged ring band stock which is inserted and clamped into a spinning die . the spinning die is rotated by a horizontally configured lathe output shaft presenting the extended portion of the flanged ring band stock for machine tool forming . standard machine tools are used to form the flanged ring band stock into a circular flanged ring including the smacna t 24 flanged ring profile . a circular flanged ring is cut along a diameter into semi - circular flanged ring portions ; straight segments including segments with smacna t 24 linear segments are roll formed , assembled into a oval shape within a fixture and welded forming the oval flanged ring . the method of making and the circular and oval flanged rings are disclosed .