The Scratch Hardness of Toughened Plate Glass
JSGT_1935_V19_T221_T230
Experiments have been made, under five different sets of conditions, on the cuts or scratches produced on both ordinary plate glass and on toughened (Armour plate type) glass. In three, the cutting agent was a diamond; in two, a tungsten alloy wheel, different loads being used in different cases. Under the same cutting conditions, the width of scratch was nearly the same for ordinary plate as for toughened glass, but whereas it was uniform all over the surface of ordinary plate, the width diminished by approximately 25% near the edges of the toughened sheet. The note emitted by the cutting tool was different in the two cases. The cut was cleaner in the case of the toughened glass: but after an interval of time, in length dependent on the cutting load, the sides of the cut underwent splintering. The splinters produced were curved, and from this curvature calculations were made which indicated that the tensile stress at the centre of the sheet varied from 1·0 to 5·3×104 kg/cm2. Numerical data and photomicrographs are given.
A. J.Holland & W. E. S. Turner
