Holding tools (other)
Nuts & bolts
Layout & testing
Layout, using paterns
Lumber & lumbering
Measuring with rule
Nails for woodwork
Structure of wood
Try square usage
The vernier principle
has long been applied to a measuring tool to which it gave its name,
the vernier calipers.
It is used for accurate measuring,
much as a micrometer is used.
The fact that the head of the vernier
calipers can be moved along the bar makes its range of measurement
much greater than that of a micrometer.
While the vernier principle
is, of course, the same whether used on the micrometer or on the
vernier caliper, there is a difference in application. On the micrometer,
the vernier remains stationary and the scale is moved. On the vernier
caliper, the scale is fixed and the vernier plate, attached to the
adjustable jaw, moves with it.
This vernier plate has 25 graduations
on it. The sum of the length of these 25 graduations is equal to
the sum of 24 graduations on the bar. Each of the divisions on the
bar is .025 inch long because the inch has been divided into forty
parts. Just as the vernier on the micrometer indicated tenths of
divisions, this vernier indicates twenty-fifths of a division.
A twenty-fifth of .025 is 1 one-thousandth,
so we read thousandths on the vernier scale. These thousandths are added
to the reading on the bar. A vernier setting which indicates 1.436"
is obtained by noting the exposed figure 1. The line over the 0 on the
vernier is one division past the 4, so we mark down the 4, and the reading
is then 1.4.
To this we add the one division which is
equal to .025 and so obtain 1.425. To this is added the number of the
line on the vernier which coincides with a line on the scale. This number
is 11; that is, .011. Adding this to the 1.425 we get 1.436".