Measuring With A Depth Gage

depth gage

Depth gages typically consist of short-range indicating devices mounted through a plate or a reference bar. They are among the simplest indicator gages that are used in thousands of critical applications. Depth gages are used to measure the depth of recesses, holes, slots, counter bores, cavities, and other component features. Depending on the specific application, they are available in various configurations.

Understanding the Different Categories of Depth Gages

There are different depth gage categories and they include:

  • Vernier depth gages
  • Combination depth angle gages
  • Depth rulers
  • Flush-pin gages
  • Thread depth gages
  • Depth micrometers
  • Digital depth gages
  • Dial gages

All of these gages are designed to be hand-held or portable, which means that you bring the gage to the workpiece. However, if a part is small, it would be more convenient to bring the part to the gage. In order to really understand depth gages better, we will discuss the specifications of each type of depth gage and their features.

Dial Depth Gages

Dial depth gages use a needle or pointer that’s mounted in a gradual disc-dial to display data. The dial indicates positions and dimensions from a reference point. Examples of depth gage graduations are 50-0-50, 4-0-4, 45-0-45, and 10-0-10. Dial display options include an analog amplifier, one or multi-revolution capabilities, and clockwise and counter-clockwise rotation.

Digital Depth Gages

These gages present metrological data in alphanumeric or numeric form. A digital depth gage often has a data output capability that uses the serial or other formats.

Thread Depth Gages

This instrument measures the depth of a thread and its quality with NOGO and GO gages. Thread depth gages are simple, inexpensive, time saving and a convenient way of measuring two times the major thread diameter. The device has an LCD display, which also has a locking device to measure sleeves whenever required. It can also show readings with accuracy of up to 0.05mm.

Flush-Pin Gages

Flush-pin gages are used to measure the depth of holes or shoulders. They are also used to inspect counter shanks and counter bores. These gages are available in customizable designs depending on specific applications. They can be GO or NOGO functional gages and are used to rapidly assess the depth of openings.

Depth Rulers

These are used where precision is not a high priority. Depth rulers allow for quick measurements.

Combination Depth Angle Gages

These types of depth gages are used to indicate the orientation and depth of a hole.

Vernier Depth Gages

Vernier depth gages have a scale that increases the level of precision when taking measurements. The graduations are printed or engraved onto a surface (drum or linear).

Pro Tips When Using Depth Gages

Regardless of the depth gage you are using, it is important to adhere to some basic rules if you want to achieve consistent measurements. These rules include:

  • Always ensure that the reference head or the cross bar is clean as well as free of burrs and nicks.
  • The manual gage should be held flat and square to the reference surface. Not doing this will cause errors in readings.
  • You need to be careful when measuring the depth of holes. Avoid measuring along the hypotenuse of a triangle.

by George Chitos

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