Effect of wheel angles on the cut edges of glass
Another factor to consider in selecting the proper wheel angle is the "edge". The objective of good glass cutting is to produce an edge which is flat and relatively free of irregularities such as "shark teeth".
Shark teeth are the occasional deep spikes in the edge and are accompanied with flakes or tiny chips on the surface. A three mm thick glass scored with a sharp wheel (114°) will produce this effect. This edge irregularity may lead to failure during the life of a window.
A three mm thick glass scored with a proper angle (134°) of wheel, will produce a fissure that is made up of individual "hackles" which overlap one another. They have a unique semi-circular shape and indicate the direction of the cutting wheel. With proper pressure the edge will be relatively free of irregularities and without shark teeth.
Prepared from information supplied by the Fletcher-Terry company