The measurement error caused by the stylus position deviation in the double-disc involute measuring intrument was analyzed

and two methods

the test method and the error compensation method

for adjusting the stylus position accurately were introduced. In test method

with the angle of tooth profile being less than its real value when the stylus deviates the rails surface

the same involute tooth profile is measured repeatedly when the stylus is at different positions. The result shows that the stylus is in the best position when the angle of the tooth profile is maximal. In the error compensation method

the involute tooth profile is measured when the stylus is at two different positions over the rails

the results are compensated by attempting different values of the stylus deviation to get two results same

and the real deviation value can be obtained. The limited deviations of the two methods for adjusting the stylus position are ±0.010 mm and ±0.015 mm

which can meet demands for measuring level 1(GB/T10 095.1-2 001) involute tooth profile.