Dial Test Indicator -FITTER ONLINE NOTE

 What is Dial Test Indicator  

1- In various manufacturing contexts an indicator is any of various instruments used to accurately measure small distances , and amplify them to make them more obvious . 

2- Many indicators have a dial display , in which a needle points to graduations in a circular array around the dial .

3- Dial test indicators are instruments of high precision, used for comparing and determining the variation in the sizes of a component. 

4- These instruments cannot give the direct reading of the sizes like micrometers and vernier calipers. 

5- A dial test indicator magnifies small variations in sizes by means of a pointer on a graduated dial. 

6- This direct reading of the deviations gives an accurate picture of the conditions of the parts being tested. 

7- Indicators , of which there are several types , therefore are often called dial indicators . 

Types of Dial Test Indicator 

1- A dial test indicator , also known as a lever arm test indicator or finger indicator , has a smaller measuring range than a standard dial indicator .

1- A test indicator measures the deflection of the arm , the probe does not retract but swings in an arc around its hinge point . 

2- The lever may be interchanged for length or ball diameter , and permits measurements to be taken in narrow grooves and small bores , where the body of a probe type may not reach . 

3- The model shown is bidirectional , some types may have to be switched via a side lever to be able to measure in the opposite direction . 

Types of Dial Test Indicator 

There are two types of dial test indicator , 

i- Plunger type , 

ii- Lever type . 

i- Plunger Type Dial Test Indicator 

Converting the linear motion of the plunger, a rack and pinion mechanism is used .

ii- Lever Type Dial Test Indicator 

1- The magnification of the movement is obtained by the mechanism of the lever and scroll .

2- It has a ball - type contact and it has an oscillating movement as against the reciprocating movements in the plunger type indicator .

3- It can be conveniently mounted on a surface gauge stand , and can be used in places where the plunger type dial test indicator application is difficult to use . 

Usage of Dial Test Indicator 

1- To compare the dimensions of a work piece against a known standard ,slip gauges . 

2- To check plane surfaces for parallelism and flatness . 

3- To check straightness of shafts and bars. 

4- To check concentricity of holes and shafts .

Principle of working 

The magnification of the small movement of the plunger or stylus is converted into a rotary motion of the pointer on a circular scale. 

Important features of dial test indicators 

1- An important feature of the dial test indicator is that the scale can be rotated by a ring bezel, enabling it to be set readily to zero. 

2- Many dial test indicators read plus in clockwise direction from zero, and minus in the anti-clockwise direction so as to give plus and minus indications. 

Uses

1- To compare the dimensions of a work piece against a known standard,slip gauges. 

2- To check plane surfaces for parallelism and flatness. 

3- To check parallelism of shafts and bars. 

4- To check concentricity of holes and shafts.

Care and maintenance of dial test indicator 

1- Keep the dial test indicator spindle and point clean using a soft cloth. 

2- Store the dial test indicator in a safe, dry place and cover them to keep the dust and moisture out. 

3- Do the dial test indicator under gaging conditions at intervals during the operating day.

Digital dial Test indicator 

1- With the advent of electronics, the clock face (dial) has been replaced in some indicators with digital displays (usually LCDS) and the clockwork has been replaced by linear encoders. 

2- Digital indicators have some advantages over their analog predecessors. 

3- Many models of digital indicator can record and transmit the data electronically to a computer, through an interface such as RS-232 or USB. 

3- This electronic digital indicator has a 1-3/4 inch.

1- LCD display, with a measuring range of SAE: (0-1 in.), Metric: (0-25mm) and accuracy of +/- 0.001 in. 

2- The digital indicator's extra features include a quick reset button, a manual on/off button and a hardened steel contact point. 

3- This digital indicator is perfect for minor projects. 

i- 1-3/4 in. LCD display.

ii- Measuring range: SAE: (0-1 in.), Metric: (0-25mm).

iii- Accuracy: +/- 0.001 in. 

iv- Quick reset button .

v- Manual on/off button.

vi- Hardened steel contact point.