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The Fundamentals of Dial indicators

The Fundamentals of Dial indicators

THE FUNDAMENTALSOF DIAL INDICATORS

Dial Indicators are used throughout industry on gauge fixtures, indicator stands and on mag bases to measure both static and dynamic features.
Dial Indicators are available in several dial sizes, graduations and spindle travel.
Electronic Indicators have a variety of functions such as Max/Min/TIR, and outputs that can be used for remote access.

Dial Face Size: Dial Indicators are available in a variety of dial face sizes ranging from series 0 to series 4, with series two (2 to 2-3/8" diameter face) being the most common size.

Mounting: Dial Indicators can be mounted by their mounting stem or by using special mounting backs. The mounting stem is available in either 3/8" Ø or 8mm Ø for full metric indicators. A hybrid metric indicator with a 3/8" stem is also available to fit American gauge fixtures. Indicator mounting backs are available in many different configurations, with the lug back being the most common.

Dial Indicator Points: The standard thread on an AGD style indicator point is #4-48. Metric indicators use M2.5 x 0.45. Indicator points will normally interchange between different brands of indicators.

Bearings and Jewels: Dial Indicators use either plain bearings, bushings or jeweled bearings. Jeweled bearings are recommended for indicators subject to high usage and indicators graduated in .0001".

Dial Indicator Accuracy: American Gauge Design (AGD) Specifications require that a dial indicator be accurate to within ± one graduation in the first 2-1/3 revolutions of the dial face.


Graduations and Range: Dial Indicator graduations range from .00002" to .010" and spindle travel from .001" to 12". Long-range indicators (over one inch) are subject to accuracy errors due to cosine error (a mounting problem) and gear train error (over a long distance).

Dial Face Styles: Dial Indicators are available in four general types of dial faces: Balanced, Continuous, Reversed (continuous), and Single Revolution.

The dial face may also have a revolution counter. Balanced and single rev dial faces are normally used on gauge fixtures for a run of parts or to check for TIR. A continuous dial face is normally used to measure the dimension of a feature.

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