Gear Inspection

Gear tooth vernier caliper is used to measure the thickness of gear teeth at the pitch line or chordal thickness of teeth and the distance from top of tooth to the chord. The thickness of a tooth at pitch line and addendum is measured by an adjustable tongue, each of which is adjusted independently by adjusting screw on graduated bars. The effect of zero error should be taken into consideration. This method is simple and inexpensive but time consuming.

It needs different setting for variation in number of teeth for a given pitch and accuracy is limited by the least count of instrument. Since the wear during use is concentrated on the two jaws, the caliper has to be calibrated at regular intervals to maintain the accuracy of measurement.

Gear is then inspected for runout. Runout means the eccentricity in the reference or pitch circle. Gears that are eccentric tend to have a vibration per revolution. A badly eccentric tooth may cause an abrupt gear failure. The runout in gears is measured by gear eccentricity testers. The gear is held on a mandrel in the centers and the dial indicator of the tester posseses a special tip descending upon the module of gear being tested. The tip is inserted in between the tooth spaces. The gear is rotated tooth by tooth. The maximum variation is noted from the dial indicator reading and it gives the runout of the gear.