Page 70 - CITS - Fitter - Trade Theory

FITTER - CITS

Dial test indicator

Definition of dial test indicator:

Dial test indicators are instruments of high prescision, used for comparing and determining the variation in the
sizes of a component. (Fig 1) These instruments cannot give the direct reading of the sizes like micrometres and
Vernier callipers. A dial test indicator magnifies small variations in sizes by means of a pointer on a graduated dial.
This direct reading of the deviations gives an accurate picture of the conditions of the parts being tested.

Types of dial test indicator
Two types of dial test indicator are in use:

1 Plunger type dial test indicator.
2 Lever type dial test indicator.
1 Plunger type dial test indicator: As described earlier, a plunger type dial test indicator features a probe or
stylus mounted on a spring-loaded plunger mechanism. The movement of the object being measured causes
the stylus to move, which in turn compresses or extends the plunger against a spring. This linear motion of the
plunger is then translated into rotational motion, which is indicated by the dial.
2. Lever type dial test indicator: In a lever type dial test indicator, the stylus is connected to a lever mechanism
rather than a plunger. As the stylus makes contact with the object being measured, it causes the lever to pivot.
The movement of the lever is then amplified and transferred to the dial indicator via a system of gears or
linkages, resulting in the indication of the measurement on the dial face.

Parts of dial test indicator
It’s part’s:
1 Pointer
2 Rotatable bevel

3 Bezel clamp
4 Back lug
5 Transparent dial cover
6 Stem

7 Plunger
8 Anvil
9 Revolution counter

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CITS : CG & M - Fitter - Lesson 10 CITS : CG & M - Fitter - Lesson 10