Both the dial and
vernier calipers are almost always configured to permit inside as well as
outside measurements. In addition, while dial-equipped slide
calipers can be read directly for both outside and inside
measurements, on those with a vernier scale.
Scale account has to be taken of the width of the “nibs�?used for
inside measurements. This dimension has to be subtracted from the
final reading to obtain the true dimension of the hole. (Note,
too, that the width of the nibs sets a lower limit to the diameter
of gap they can enter. )