| 摘要 |
PURPOSE:To maintain a degree of flatness in a surface plate ever so longer as well as to make the promotion of high-grade precision in finishing size accuracy and surface accuracy of a work attainable, by forming a ringlike groove in a surface opposed to a work part of the surface plate. CONSTITUTION:A groove is installed in a part equivalent to an almost anpex part coming to a convex form by a central part on a radius of a surface plate 1, namely, dead load and a lap ring 4 and the imposition of load 3 whereby an abrasive grain 7, a work 5 and a correction ring 2 hit this groove edge part during lapping so that also this edge part comes to be lapped in consequence. Therefore, with this edge part lapped like this, the radial central part tends to become a concave form. Witn this constitution, an upper side of a section in radial direction passing the center of the surface plate installing a grooveless or uniform groove in a spiral form comes to a convex form but in case of a center-groove surface plate, it comes to a concave form. Thus, since maintenance of a degree of surface flatness is prolongable, a surface plate change cycle and correction time are sharply prolonged or reduced. |
