Gramophone record groove cutting needle - has flat cutting surface connected to two free surfaces via radiused polishing surfaces

摘要

The cutting needle (30) is used for production of grooves in gramophone records. It has a single cutting surface (31) on its front side, and there are two free surfaces (34) behind the cutting surface. The adjacent margins (32,35) of these two surfaces are connected by a curved surface (33). The cutting surface (31) on the front is vertical, and the free surfaces (34) lie at an angle. The curved surfaces (33) are arcs of a circle, of radius equal to that of the spherical needle lip used for playing the record. The axis of the circles lie in the hypothetical cutting plane at right angles to the flat free surfaces (34).PS.