Calipers (or vernier calipers, after Pierre Vernier, inventor of the kind
of graduated scale used to improve their accuracy) are useful for
making accurate measurements of small objects. Place the object in the
jaws of the caliper and squeeze very gently. If the object is
round, rotate the object to be sure you don't apply to much force to the
jaws. The object should rotate easily.
To read the scale, look at the left end of the lower scale, as shown in the inset. It sits about halfway between 2.0 and 2.1, so the reading is about 2.05. To do a better job of estimating that final digit, look along the ticks of the bottom scale, which are not spaced at the same interval as those of the main scale. Find the tick that from the bottom scale that lines up best with a tick on the upper scale. In this case, it is the sixth tick. This is the final digit of the measurement. So, the best estimate of the size of the ball bearing, in this case, is 2.06 cm.
Updated 6/17/99 by Peter N. Saeta .