The head of the machine is Tilted over to mill the curve on the front.
The following calculations were used for setting the head.
For a Radius of Curvature of 96" and a cutter of 4" diameter, the angle is 1.19 degrees. This cannot be set accurately on the Bridgeport. However as the blanks would be ground on cast iron tools made to the exact radius it did not matter.
The machine table must be fed up to keep the outer edge
of the ciamond cutter on the centre of the glass blank, not the quill
fed down at the angle it is set at. I milled the backs flat and the
front curve of the ten 8" blanks in one day. Fast, easy and clean. Since
I have milled twenty 6" blanks. I experienced chipping of the edge on
the 6" blanks but not on the 8". I put this down to the segmented edge
of the cutter and the smaller diameter of the 6" blanks. However the
chipped edges were quickly fixed with bevelling tool described in (Bevelling