OBJECTIVE. To become familiar with the use of common engineering metrology instruments.

PREPATORY READING. Kalpakjian & Schmid, ch. 35.

EQUIPMENT. Inch micrometer, dial calipers, steel rule, and micrometer depth gage.

Students are expected to learn how to use these instruments through this lab. Over the semester,

students will have the opportunity to use these instruments during the machining labs.

Students are responsible to clean their work area at the end of each lab session. Failure to clean

the lab will result in grade penalties.

Metrology is the science of engineering measurements such as length, thickness, diameter, angle,

straightness, mass, etc. The ability to measure these attributes is necessary to ensure the fit and

function of components in engineered assemblies. No part is ever made exactly to specification,

as there is always an unavoidable variation in feature sizing. As a result, part features are

specified with a nominal (or basic) size, with an allowable deviation away from that nominal


Inspection is the process of comparing actual part features against the specified feature size. A

variety of instruments and gages may be used for part inspection, and many are available in this

lab. Knowledge of five basic instruments is sufficient for most engineering applications.

  • Steel rule provides an inexpensive means of low-resolution feature measurement.
  • Inch micrometer provides measurement of outside features up to one inch across.
  • Vernier calipers usually measure to 6 inches, and can measure inches and millimeters


  • Dial calipers can measure outside features, inside features, and depths. They are easier

to read than vernier calipers.

  • Height gage measures distance from a reference plane, usually a granite surface plate. A

height gage can have a vernier, dial, or electronic readout.

  • Micrometer depth gage measures depth from a reference plane, which is usually more

accurate than calipers.

PROCEDURES. Finish the assigned reading before lab. The lab instructor will explain how to

use these measurement tools. Students will use these tools to read the required dimensions of the

provided part.

The instructor will also demonstrate how to properly read vernier and dial gages on the

instruments. For each instrument, the student should note its range and resolution. Students

should be comfortable using these instruments, as they will be used in later lab sessions. Each


student should be able to make his own measurements. Use the instruments as much as necessary

to become comfortable measuring features on the parts.

CLEAN UP. Clean up the lab area and return equipment to its proper location.

LAB REPORT. Present your measurements in a table. Suggest to include the following

discussions in the lab report:

  • Discuss the range, resolution, and intended use of the inch micrometer and the dial

caliper used in this lab. Do certain instruments work better than others for some


  • Include a brief engineering drawing of this spur gear without the tooth profile, and label

the dimensions measured. Use your best engineering judgment if you have the same

dimension measured by different ways or by different tools.

  • Are the repeated readings the same? Why?



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