Page 59 - Turner 1st sem Practicals

Job sequence

• Take different instrument to measure different jobs and • Record the measurement in table.
fill the table.

Skill sequence

Measuring with inside and outside calipers

Objectives: This shall help to
• select the right capacity caliper for measurement
• set the sizes both in firm joint and spring calipers
• read the sizes by transferring them to a steel rule or other precision measuring devices as the case may be.

Outside calipers: Select a caliper based on the diameter
to be measured.
A 150 mm capacity outside caliper is able to measure
sizes from 0-150 mm.
Open out the jaws of the calipers until they pass clearly
over the diameter to be measured. The work must be
stationary when measuring the sizes. (Fig 1)

When you have adjusted the outside caliper for the correct
‘feel’ transfer the measurement to a steel rule or any other
precision measuring instrument as the case may be.

Keep the graduated steel rule on a flat surface and hold the
Place one point of the leg over the workpiece and get the point of one jaw firmly against the rule end. (Fig 4)
sense of feel of the other point of the leg.
If there is clearance on the other point of the leg, gently tap
the back of one leg of the firm joint calipers on a wooden
piece until it just slips from the external diameter of the
workpiece to give the right sense of ‘feel’. (Fig 2)

Because the accuracy of reading depends mainly upon the
sense of feel of the user, high care should be exercised to
get the correct `feel'.

The point of one jaw must be placed over the graduation so
that the point of the other jaw is parallel with the edge of
the steel rule.

Record the reading to an accuracy of ±0.5 mm.
In the case of precision measurements, transfer the
measurements over an inside micrometer or vernier caliper.
This measurement will give an accuracy of ± 0.01 or ± 0.02
mm. Here, the sense of feel of the user is very important in
In the case of spring outside calipers, adjust the screw nut deciding the reading.
so that the adjustment of the jaws just slips from the Inside caliper: Open out the jaws slightly less than the
external diameter of the workpiece to give the right sense size to be measured.
of feel. (Fig 3)
Producltion & Manufacturing : Turner - Exercise 1.2.16 47