PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
4 Prior to putting a vernier gage away, wipe it clean and
give it a light coat of oil. (Perspiration from the hands will cause the
instrument to corrode rapidly.)
(b) Use. The most accurate means of using the height gage is to
place the workpiece on the top of the surface plate.
After the correct
setting has been made, place the base of the vernier height gage on the
surface plate and scribe the desired height onto the workpiece.
(4) Depth Gages.
A depth gage is an instrument for measuring the
depth of holes, slots, counter bores, recesses, and the distance from the
surface to some recessed part. The most commonly used depth gages are the
vernier depth gage, the rule depth gage, and the micrometer depth gage.
(a) Vernier Depth Gage. The vernier depth gage (figure 5 on the
following page) consists of a graduated scale (1) either 6 or 12 inches
long.
It also has a sliding head (2) similar to the one on the vernier
caliper.
The sliding head is designed to bridge holes and slots.
The
vernier depth gage has the range of the rule depth gage. It does not have
quite the accuracy of a micrometer depth gage. It cannot enter holes less
than 1/4 inch in diameter. However, it will enter a 1/32 inch slot. The
vernier scale is adjustable and may be adjusted to compensate for wear.
(b) The Rule Depth Gage. The rule depth gage is a graduated rule
with a sliding head designed to bridge a hole or slot, and to hold the rule
perpendicular to the surface on which the measurement is taken. This gage
has a measuring range of 0 to 5 inches.
The sliding head has a clamping
screw so that it may be clamped in any position.
The sliding head has a
flat base which is perpendicular to the axis of the rule and ranges in size
from 2 to 2 5/8 inches in width and from 1/8 to 1/4 inch in thickness.
(c) Micrometer Depth Gage. The micrometer depth gage consists of
a flat base attached to the barrel (sleeve) of a micrometer head.
These
gages have a range of 0 to 9 inches, depending on the length of the
extension rod used. The hollow micrometer screw (the threads on which the
thimble rotates) has a range of either 1/2 or 1 inch. Some
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