A double-disc mode instrument for measuring involute tooth profile is analyzed

which has some advantages

such as simple structure

no Abbe error caused by the stylus

etc. The instrument adopts an intersect coach spring structure as the error transfer lever

which has high sensitivity and no gap. After compensating major measurement error sources

the double-disc mode instrument's uncertainty of measurement (U

95

) is less than ±0.5 μm

which can meet measurement specification of the involute tooth profile of level 1 gear. Comparing with CNC instruments for measuring gear tooth profile

the double-disc instrument's automation and multifunction performance are insufficient

but it has advantages in accuracy of measurement and manufacturing economical efficiency

etc. The result shows that the double-disc mode is an ideal method for measuring ultraprecision involute tooth profile.