Method for testing eccentricity of a testing point from a reference point on a thread to be tested, especially a screw

摘要

A method for testing eccentricity of a testing point (16) from a reference point (14) on a threaded part (11) to be tested, especially a screw, provides that a ring gauge (1) provided with an internal thread (2) is inserted with its zero axis (4) into a testing device in such a way that the position of its zero axis (4) is known at the testing device. The threaded part (11) is screwed together with the reference point (14) constructed as an external thread into the ring gauge (1), and measured values are determined over the circumference at the testing point (16), in order to reach conclusions from this on the eccentricity of the testing point (16) from the reference point (14). Use is made of a ring gauge (1) whose internal thread (2) has a play at the reference point (14) with respect to the external thread (12) of the threaded part (11). The threaded part (11) is purposively tilted with respect to the ring gauge (1) by means of a radial force application until the flanks of the external thread (12) and internal thread (2) are supported. With this tilt maintained, measured values are recorded over the circumference of the testing point (16), and these measured values are used in conjunction with a mathematical model to determine the position of the centre of gravity (18) of the testing point (16) at this tilt. The threaded part (11) is tilted successively in a plurality of different radial directions, and in each case the positions of the centre of gravity (18) of the testing point (16) is determined in the manner described. The positions of the centre of gravity at the various tilts are used in conjunction with a mathematical model to calculate the principal centre of gravity whose distance from the zero axis (4) is then a measure of the eccentricity.