Question

What is backlash error? How do we prevent it? $\left[3\text{marks}\right]$

Answer 1

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• On reversing the direction of rotation of the thimble, the tip of the screw may not move in the opposite direction immediately but remain stationary for a part of the rotation; this leads to an error in measurement called backlash error.

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• It happens due to the wear and tear of the screw threads or when there is a gap between the trailing face of the driving tooth and the leading face of the tooth behind the driven gear.

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• To avoid the backlash error, while taking the measurements the screw should be rotated in one direction only. If the direction of rotation of the screw needs to be changed, then it should be stopped for a while and then rotated in the reverse direction.