Depth gauge
Depth gauge:
Vernier Depth Gauge as the name suggests is used to measure the depth from the surface of reference of an
object. Vernier caliper also has depth bar but this cannot be used as the standard measurement.
A depth gauge typical refers to is a precision measurement instrument that is used by mechanical engineers,
manufacturing engineers, and machinists among others, to accurately obtain the measurement of the depth of
a bored cavity, recess, hole, groove or other similar openings that were created below the surface level of a
material.
Types of depth gauge:
There are several different types of depth gauges available. The primary types include:
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Analog (dial) depth gauges
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Digital depth gauges
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Depth gauge micrometers
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Depth rulers
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Vernier style depth gauges
Analog (dial) depth gauges:
Analog or dial-type depth gauges feature a mechanical dial and needle indicator to illustrate the depth
measurement on the dial face.
Digital depth gauges:
Digital depth gauges, also called electronic depth gauges, replace the dial and needle indicator that is used
with dial depth gauges, substituting a digital display that directly indicates the measured depth directly with
a given number of digits. Because there is an electronic display used, a power source – typically a battery –
is needed to power these instruments.
Depth gauge micrometers:
Depth gauge micrometers provide a depth measure and have a rachet that can be turned to move the spindle
face into the recessed opening until it contacts the bottom of the hole. The thimble and sleeve on the depth
gauge micrometer are identical to those found on a standard micrometer and reading the value of depth is
performed in the same manner.
Depth rulers:
Depth rulers, also called rule depth gauges, are a simpler form of depth gauge that features a graduated
straight scale or ruler affixed to a locking bolt that can be raised and lowered into the recess to obtain a
reading of depth. Some models of depth ruler allow the user to rotate the orientation of the scale relative to
the plane of the base surface, thus being able to be used to measure both the depth of the opening as well as
its angular position. The resolution of depth rulers is generally lower than that of other types of depth
gauges.
Vernier style depth gauges:
Vernier style depth gages use a Vernier scale concept like that which is used on a Vernier caliber. The use of
the Vernier scale permits the operator to obtain additional precision of depth readings using mechanical
interpolation off the Vernier scale against the main scale. To learn more about how to read a Vernier scale,
please check-out this reference. Vernier scales allow for precise measurements without the need to add
additional graduation marks on the main scale which, at some point, renders the instrument unreadable.
Working principle of depth gauge:

Vernier depth gauge is used for measuring the depth of holes, recesses and distances from a plane
surface to a projection.
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Here the graduated scale is slide through the base and vernier scale remains fixed..
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The depth gauge is made precisely so that the beam is perpendicular to the base in both
directions
Step for using depth gauge:
 Thoroughly clean and inspect the attachment.
 Fasten it to the movable jaw.
 Set the depth gauge rod with its end in contact with the surface plate.
 Write down the reading, do not depend on memory.
 Raise the movable jaw to clear the obstruction on the part.
 Place height gauge in position and lower movable jaw until rod of the depth gauge contacts the
measured point of the part feature.
 Note the reading. The difference between this reading and the reading in step 4 is the height of the
measured point above the reference surface.
Errors in Using the Depth Gauge:
The most common errors are listed below:
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
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Gauge is imperceptibly tipped.
The base is liſted when a measured point is slid with pressure.
Point pressure carts the base a trifle.