| 摘要 |
PURPOSE:To reduce form deterioration in a surface plate as well as to make highly accurate machining for a long time attainable, by constituting the surface plate with alumina as a main component, while setting it down to bulk specific gravity in design. CONSTITUTION:When service life in a lapping surface plate is compared with a fact that straightness in a machined surface defines the machined number of items satisfying a value of 0.05mum/4mm., the case of using an alumina ceramic is favorable more than two times over 400 pieces against 100-200 pieces in case of a thn lap. In case of bulk specific gravity being higher as much as 3.9, a machining step difference is large or 0.05-0.07mum, that is in proportion as the bulk specific gravity comes smaller, the machining step difference is also small, coming into the minimum at somewhere around 3.55 in the bulk specific gravity but is further it comes smaller, the step difference reversely becomes large so that the bulk specific gravity of 3.4- 3.8 is the optimum range. Next, the lapping surface plate is made by an alumina ceramic of 3.55 in the bulk specific gravity, while a lapping surface (a) is installed in an upper part 1, and an induction groove 3 of cooling or heating fluid, a fluid intake port 4 and also a fluid discharge port 5 are all installed in a lower part 2, then both upper and lower parts are solidified in one by means of molding join. Thus such a surface plate as being excellent in flatness on the machining surface and small in deformation due to temperature change is securable. |
