Cutting stylus for mechanically cutting masters for keel-lapping

A cutting stylus for cutting a fully shaped groove in a metal substrate as a step in a process for lapping a keel on a playback stylus, said playback stylus being suitable for playing back prerecorded signals from a disc record groove of a given width, said keel being defined by a constricted terminal region on the tip of said playback stylus, said constricted terminal region being narrower than said given groove width, said cutting stylus comprising:

• a support body;
• a protrusion defined by a constricted terminal region;
• and
• shoulders joining said protrusion to said support body;
• said protrusion including;
• a flat cutting face having a shoulder end and a distal end;
• a pair of side surfaces extending from side cutting edges of said flat cutting face, said side cutting edges being tapered to form said protrusion such that said cutting face has a beveled contour having a first thickness proximate to said shoulder end and a second thickness which is less than said first thickness proximate said distal end;
• and
• a bottom surface extending from a bottom cutting edge of said flat cutting face;
• wherein said side surfaces taper at an angle of 1 to 3 degrees such that clearance is provided to said side cutting edges during the cutting operation and said bottom surface is formed such that a clearance angle of 5 to 10 degrees is provided to said bottom cutting edge during the cutting operation;
• wherein said flat cutting face of said protrusion has dimensions of approximately 4 .mu.m deep by 2 .mu.m wide;
• whereby said groove in said metal master is cut, in a single pass across a surface of said metal master, having a contour that is the same as the contour of said cutting face.