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Gaging & Inspection Tool Design

Use this page to learn more about this topic and find additional resources.

This page will offer resources and information that will help you better understand the basic aspects of gaging and inspection tool device design. Here are a few of the subjects that will be covered on this page:

  • Tolerances and Allowances
  • Gage Tolerances
  • Gage Types
  • Magnifying/Amplifying Dimensions

Tolerances and Allowances

Because of the limits of manufacturing, all part dimensions are made within a specified working tolerance, which is the total permissible amount by which a dimension may vary from a specified size. When providing tolerances, designers recognize that no two workpieces, distances, or quantities can be exactly alike.

Gage Tolerances

Gage tolerance is expressed as a percentage of workpiece tolerance. For fixed, limit-type working gages, gage tolerance is generally set at 10% of workpiece tolerance. The tolerance of inspection gages is usually 5% of work tolerance. Master gages, those used to check the accuracy of other gages, are usually 10% of gage tolerance.

Gage Types

A wide variety of gages are available to visually inspect and gage parts. A few of the basic types include:

  • Screw-pitch gages
  • Plug gages
  • Ring gages
  • Snap gages

Magnifying/Amplifying Dimensions

As dimension changes become too small for easy measurement, it is necessary to amplify or magnify them prior to measurement. This can be performed mechanically, electronically, pneumatically, or optically using a variety of tools.

Dial indicators have a contact point that is attached to a spindle or rack. When this spindle or rack is moved, it transmits that movement to a pinion and then through a train of gears. These gears magnify the movement, which is then read off the hand on the dial face of the indicator. Because the principle of direct reading from a graduated dial face provides both accuracy and speed of reading, the dial indicator has been incorporated into many types of gaging equipment.

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Additional Resources & Products

Gaging & Inspection Tool Design

Gaging and Inspection Tool Design DVD

Because of the limits of manufacturing, all nominal part dimensions require working tolerances for production. Purchase the complete DVD for the video found above on this page.
Fundamentals of Tool Design, Sixth Edition

Fundamentals of Tool Design, Sixth Edition

For over 40 years, students, designers, and manufacturing practitioners have used the Fundamentals of Tool Design to gain an in-depth understanding of all the factors that impact tool success.
Technical Papers

Tooling Design - An Integral Function of Product Design

Product design engineers must consider all phases of tooling design to arrive at the best possible product designs. This paper presents a good discussion of the correlation of tool and product design.

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