Abstract: A method of precisely controlling the amount of flatness or curvature in a lapping plate is disclosed. The lapping plate is formed from two layers of metal alloys, such as tin-antimony and steel. A bimetallic effect is exploited to induce a linear expansion in the plate so that the flatness or curvature of the plate is manipulated with thermal cycling. The plate is machined and charged under very specific and tightly controlled temperatures to produce a very robust, flat plate charge. As temperature cycling induces a linear expansion along a single plane across the plate, the resultant flatness change is scalar with temperature, and can be repeated and controlled. When the plate laps magnetic sliders, the plate can be thermally cycled to produce a conical surface and a high crown-to-camber ratio can be achieved.

Abstract: A method of predicting the lapping property of a charged lapping plate uses samples with a known lap surface. The samples are lapped on the plate and a non-invasive sensor is used to determine the lapping rate under a fixed load and rotation speed. The total frictional force of the samples is measured during the lapping to calculate the friction and Preston coefficients of the plate. The samples are held in place while the plate rotates and the sensor measures the distance to the plate. The plate rotates for a specific time so that adequate removal of the pad material has occurred. The lapping rate is determined from a change in the gap distance over a time interval. The lapping rate and friction are then assessed to determine if the plate is lapping worthy.

Abstract: A device for predicting the lapping property of a charged lapping plate uses samples with a known lap surface. The samples are lapped on the plate and a non-invasive sensor is used to determine the lapping rate under a fixed load and rotation speed. The total frictional force of the samples is measured during the lapping to calculate the friction and Preston coefficients of the plate. The samples are held in place while the plate rotates and the sensor measures the distance to the plate. The plate rotates for a specific time so that adequate removal of the pad material has occurred. The lapping rate is determined from a change in the gap distance over a time interval. The lapping rate and friction are then assessed to determine if the plate is lapping worthy.

Abstract: A system and apparatus precisely controls the amount of flatness or curvature in a lapping plate. The lapping plate is formed from two layers of metal alloys, such as tin-antimony and steel. A bimetallic effect is exploited to induce a linear expansion in the plate so that the flatness or curvature of the plate is manipulated with thermal cycling. The plate is machined and charged under very specific and tightly controlled temperatures to produce a very robust, flat plate charge. As temperature cycling induces a linear expansion along a single plane across the plate, the resultant flatness change is scalar with temperature, and can be repeated and controlled. When the plate laps magnetic sliders, the plate can be thermally cycled to produce a conical surface and a high crown-to-camber ratio can be achieved.