Collection: Grinding

In the manufacture of lenses, slabs of glass are cut with a glass saw or slitting disk; a piece of the desired type and shape is chipped to a rough, round blank, or the pieces may be heated to softness, rolled to a round shape, and pressed in a mold to the desired size and to approximately the desired curvature of the surfaces. The surfaces are then ground, or lapped, to the final form, using coarse emery, carborundum, or diamond as an abrasive. Lens surfaces are ground on an iron tool, either flat or suitably curved, using progressively finer grades of one of the abrasives mentioned above. In the grinding process, a rotating cup-shaped tool is mounted so that its axis of rotation intersects the axis of the lens at the center of curvature of the desired spherical surface. The obliquity of the tool axis must be adjusted so that the rim of the tool cuts across the center of the (concave) lens being generated. For convex lenses, the center of the rotating tool face cuts the rim of the lens blank. As both tool and lens rotate about their respective axes, a spherical surface of the desired radius of curvature is generated on the lens.