PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
inaccurate measurements.
Also
protect the
vernier caliper
points
from
damage.
(e) Vernier gages also require careful handling and proper
maintenance if they are to remain accurate.
The following instructions
apply to vernier in general:
1 Always loosen the binding screws before attempting to move
the sliding arms.
2 Never force a gage into position. Forcing, besides causing
an inaccurate reading, is likely to force the arms out of alignment.
3 When taking a measurement, use only gentle pressure on the
fine adjustment screw.
Heavy pressure will force the two scales out of
parallel.
4 Prior to putting a vernier gage away, wipe it clean and
give it a light coating of oil. (Perspiration from the hands will cause the
instrument to corrode rapidly.)
1.
Universal Vernier Bevel Protractor.
(1) General.
The universal vernier bevel protractor (figure 48 on
the following page) is used to lay out or measure angles on a workpiece to
It reads to 5 minutes or 1/20 and can be used
very close tolerances.
completely through 360ƒ. The protractor is made up of an adjustable blade
(1) and a graduated dial (2) which contains a vernier scale.
The bevel
protractor is used to establish an angle and determine its relationship to
the other surfaces.
The acute angle attachment (3) is used for measuring
acute angles separately.
The tool can be laid flat upon paper or on the
workpiece. The dial is held rigidly in position and the blade can be moved
back and forth and clamped independently of the dial.
Interpreting the
reading on the protractor is similar to the method used on the vernier
caliper.
(2) Reading the Protractor Vernier Scale.
(a) General.
The protractor vernier scale indicates every five
minutes (5") or 1/20.
Each space on the vernier scale is 5 minutes less
than two spaces on the
main scale.
When the zero on the vernier stale
exactly coincides with a
graduation
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