Civil Engineering Reference
In-Depth Information
Fig. 5.3. The lever dial test indicator.
While the lever dial indicator can be used equally effectively for inside holes
or outside surfaces, the plunger dial indicator can only be used for external
surfaces, although you can get an accessory that fixes onto the nonmoving
part of the plunger housing that will enable you to clock internal bores or sur-
faces at right angles to the plunger. The plunger dial test indicator has many
uses in the home workshop, but if you can only afford one dial test indicator I
would recommend the lever dial test indicator. It will do all you require.
While the plunger dial test indicator will actually read the movement that it
is moved, the lever dial indicator does not move the amount it actually says.
Because of the lever effect, the stylus moves less the greater the angle it is
set on, due to having a spherical end. This is called the cosine error. For this
reason the lever test indicator should be used as a comparator where each
movement of the indicator should be at the zero point on the dial. One dial
test indicator maker (Verdict) has patented a pear-shaped stylus that elimin-
ates this cosine error at angles of up to 36 degrees. However, the easiest way
to eliminate most of this error is to ensure the stylus is set parallel to the body,
not at an angle.
Setting to zero
Most dial test indicators can be set to read zero by simply turning the external
bezel that is normally fitted to the outside of the dial test indicator. The plunger
dial test indicator is also available as a digital version and this can be set to
zero at any point in its travel by pressing a button.
