GB932799A - Improvements in or relating to surface roughness measuring instruments - Google Patents

Abstract

932,799. Roughness gauges. H. W. E. VAN GRODEK, and J. HASING. Dec. 8, 1959 [Dec. 13, 1958], No. 41711/59. Class 40 (1). [Also in Groups XIX and XL (b)] A tracer system for determining geometrical surface criteria of waviness and roughness on a workpiece surface, comprises at least two tracer means T1, T2 (Fig. 6), with ends of different radii and independently axially movable towards and away from the surface, a rail G for guiding longitudinal displacement of the means T1, T2, a transmitter sensitive to axial displacement of each means T1, T2 controlling integrating or recording apparatus and a timer rendering each transmitter operable only during the period its corresponding tracer is scanning the predetermined length l between two selected points of the surface. The apparatus described is used to measure the smoothness height, defined as the shaded area between the curves Pi, Pe (Fig. 3), divided by the length lto be inspected. The curve Pi is the actual profile and is described by a sharp-pointed tracer, while the curve Pe is the course of a tracer with a larger radius of curvature, e.g. one inch. Fig. 14 shows an electrical measuring apparatus employing two tracers T1, T2 supported on pairs of leaf springs N1, N2 and carrying flat steel blades Z1, Z2 respectively arranged between coils E1' E2 and F1, F2 of inductive transducers M1, M2. A timer element switches these transducers successively to the same parts of on electric bridge as the tracers pass over the test length so that a succession of pulses for each transducer is obtained which can be passed to integrating devices, the difference between the two integrals giving a measure of the roughness. Alternatively, the movements of the two tracers may be converted into D.C. voltages acting in opposition so that the difference can be fed into an integrating device to provide a direct roughness figure. An apparatus having four tracers is also described.