Selecting a Dial Indicator on Amazon.com
A dial indicator measures small distances or objects, and uses a dial to amplify the reading so that the measurement is visible to normal eyesight. It is used wherever small and precise measurements are required, including in mechanical testing, machining, toolmaking, manufacturing, scientific research and industrial engineering. Often, a dial indicator is used in conjunction with another measuring instrument, such as a bore gauge. It is also known as a dial gauge, probe indicator, or plunger indicator.
Dial indicators are analog instruments that display readings on a mechanical dial, in contrast to electronic indicators that display readings digitally. Dial indicators measure with a plunger-type contact point that runs perpendicular to the object being tested. Test indicators, on the other hand, have a pivoting contact point that measures surface variation at a set angle. Contact points come in different shapes for specific purposes, such as needle shapes to enter small grooves, spherical shapes for point contact, or flat or cylindrical tips for other applications. Tips have standardized screw threads, typically M2.5 or #4-48, for interchangeability.
The face of a dial indicator may be continuous or balanced, specified by two or three digits. A 0-100 dial is a continuous dial that displays readings from 0 to 100 in one complete revolution, typically turning clockwise. A 0-10-0 dial is a balanced dial, showing increments from 0 at the top of the dial to 10 at the bottom, with increments reading both clockwise and counterclockwise. A balanced dial indicates the difference from a specific reference surface, while a continuous dial provides direct readings. Often, a dial face will include a smaller dial to indicate the number of revolutions of the pointer. Dial faces are built to AGD (American Gage Design) specifications.
Significant features of dial indicators include graduations, which may be in inches or millimeters as small as .00005" or .001mm; the measurement range of a single revolution, and the total range of the dial; and the stem diameter. Dial indicator manufacturers include Mitutoyo and Starrett.