PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
2 Never leave a dial indicator on any surface that will be
subjected to a shock (such as hammering on a part when dialing in on the
workpiece); an erratic and uncontrolled movement of a surface could cause
the dial to be over traveled.
3 Protect the dial when it is not being used.
Provide a
storage area where the dial will not receive accidental blows, and where
dust, oil, and chips will not come in contact with it.
4 When a dial indicator becomes sluggish or sticky in
operating, it may be either damaged or dirty. Also, one may find that the
pointer is rubbing the dial crystal or that the pointer is bent or rubbing
the dial face. A sluggish dial should never be oiled. Oil will compound
the problem. A suitable cleaning solvent should be used to remove all dirt
and residue.
(2) Vernier Caliper. A vernier caliper can be used to measure both
inside and outside dimensions.
To take a measurement, position the
appropriate sides of the jaws to the surface to be measured and read the
side marked inside or outside as required.
There is a difference in the
zero marks on the two sides that is equal to the thickness of the tips of
the two jaws, so be sure to read the correct side.
Vernier calipers are
available in sizes ranging from 6 inches to 6 feet and are graduated in
increments of thousandths (0.001) of an inch.
The scales on the vernier
calipers made by different manufacturers may vary slightly in length or
number of divisions; however, they are all read basically the same way.
Detailed instructions for reading and using the vernier calipers are covered
in paragraph k(2) beginning on page 71 of this subcourse.
(3) Vernier Height Gage.
A vernier height gage (figure 4 on the
following page) is used to lay out work for machining operations or to check
the dimensions on the surfaces of work which has been machined. The offset
scriber allows one to measure from the surface plate with readings taken
directly from the scale without having to make any calculations.
If a
straight scriber were used, the actual height would have to be calculated by
taking into account the distance between the surface plate and the zero
mark. Some models have a slot in the base for the scriber to move down to
the surface and a scale that permits direct
13
Previous Page
