How to Read Vernier Calipers
Inch Fractional and Decimal Readings
This vernier caliper has two scales which enable read-
ings to a fraction of an inch as in the case of 1/128"
graduated vernier (upper scale), or in decimals as in the
case of 1/1000" graduated vernier (lower scale).
Each division on the fractional main scale represents
1/16th of an inch. The vernier further subdivides each
division on the main scale to read 1/128 of an inch.
Each division of the decimal main scale represents one
fortieth of an inch or .025". Each fourth line marked by 1
represents .100", the line marked 2 represents .200",
and so forth. The vernier consists of 25 equal divisions
which further subdivides each division on the main
scale to .001".
1. 1/128" graduated vernier (upper scale)
Readings on the main scale................................16/16"
Vernier scale reading...........................................3/128"
Final reading...........................16/16 + 3/128 = 151/128"
2. 1/1000" graduated vernier (lower scale)
Main scale reading ............................................1.375"
Vernier scale reading......................................... .023"
Final reading ....................................................1.398"
Inch Decimal Reading Only (for Inside and
Outside Jaws)
The vernier reads inside and outside dimensions with
the same jaws. Inside measurements are taken by the
specially designed jaw construction. Because of the
.300" inside jaw thickness, the vernier is placed .300" off
from zero point. Taking this difference into account, the
final inside reading is .300" greater than the outside
reading.
Like the Vernier Caliper in the preceding column, the
vernier above also reads to 1/1000 of an inch. In this
case, however, each division on the main scale repre-
sents one-twentieth of an inch or .050". This means each
division on the main scale is twice as wide as the previ-
ous example, and therefore, the vernier must span twice
the length to read to 1/1000 of an inch.
1. Inside vernier reading (upper scale)
Reading on the main scale.................................1.200"
Vernier line coinciding with main scale line........ .018"
Final reading ....................................................1.218"
2. Outside vernier reading (lower scale)
Reading on the main scale................................. .900"
Vernier line coinciding with main scale line........ .018"
Final reading..................................................... .918"
Because of .300" inside jaw thickness,
the vernier is placed .300" off from
zero point.
Fractional Reading Vernier Scale.
1/16" on the main beam is subdivided
into eight or to 1/128".
Decimal Reading Vernier
Scale. 1/40th of an inch is
subdivided into 25 by the
vernier to read to one-
thousandth. One inch is
first divided into ten, and
then 40 graduations.
Each smallest graduation
on the main beam repre-
sents .025".
1/16" Graduations
on the main beam.
Position of the
vernier plate can
be readjusted.
.300"
Rounded inside
jaws. Thickness
.300" when closed.
CALIPERS
O-30
O-30 (2003) full size 12/8/03 10:13 PM Page 1
