The principle of a micrometer
.Determine the least count of an outside micrometer
Working principle
The micrometer works on the principle of screw and nut. The longitudinal movement of the soindle during one rotation is equal to the pitch of the screw. The movement of the spindle to the distance of the pitch or its fractions can be accurately measured on the barrel and thimble.
Graduations
In metric micrometers the pitch of the spindle thread is 0.5mm.
Thereby, in one rotation of the thimble, the spindle advances by 0.5mm
On the barrel a 25mm long datum line is marked. This line is further graduated to millimeters and half millimeters(i.e 1mm&0.5mm). The graduations are numbered as 0,5,10,20&25mm.
The circumference of the bevel edge of the thimble is graduated into 50 divisions and marked 0-5-10-15.......45-50 in a clockwise direction. The distance moved by the spindle during one rotation of the thimble is 0.5mm. Movement of one division of the thimble
=0.5*1/50
=0.01mm
Accuracy or least count of a metric outside micrometer is 0.01mm.
No comments:
Post a Comment