What is Dial Indicator?

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Dial indicators can be defined as the small measuring instrument that can be used in several mechanical means to measure a certain deviation of a mechanical component. In terms of various components of a Dial indicator, it is made by pinions, levers as well as gears. Although, it can be asserted that a dial indicator is mostly used by an operator for measuring the deviation of a linear surface. Also, the actual use of this measuring device is a comparator. Therefore, dial indicators compare the deviation of a finished device with the value of a standard device which helps the operators to ensure that the value of the finished device is within the desired tolerance value.

Parts of a Dial indicator

To recognize the working principle of a Dial indicator, the operator has to aware of its comparator’s parts. Therefore, some most basic and essential parts of a Dial indicator are briefly discussed below;

Dial and Needle

It is the most basic part of a Dial indicator as it is very essential to make the contact with the surface which has to be measured with the Dial indicator. Also, needle and dial track can every minute increment that takes place within the machine component and then it can be measured by the indicator.

Plunger

The plunger is quite like a spring that moves perpendicularly with respect to the surface, which can be measured by the operator. Therefore, the operator measures the movement of the plunger, which represents the results of the existing deviation.

Needle with the clock face

This part of the dial indicator records all the data that are achieved with the help of the measurement of linear surface. Also, it is quite small in size as compared to the needle embedded dial.

Working principle of Dial indicator

The prior component of the Dial indicator, plunger carry a rack in its back and slides over the bearing to create the contact between rack and pinion. The plunger is attached within the dial indicator in such a way so that it can rotate to its axis. Therefore, for securing the precision level of the measurement, a pin can be used by operators to restrict the same. The pin is mounted by operators for guidance. Apart from that, the plunger remains at its position with the help of coil spring. Pinion at the rack made the connection between them and the gear rotates which is mounted on the same spindle. Hence, the gear and pinion are meshed with each other to magnify the measurement. After that, the second gear has meshed with the second pinion and those have meshed with the third pinion. Therefore, the process ends here and the magnification can be recorded by the operator.

The final magnification takes place is;

Ng2/ Np3 × Ng1/Np2

Where,

g2= gear two

g1= gear one

p1= pinion one

P2= pinion two

Advantages and Disadvantages

As a comparator Dial indicator can widely be used in the mechanical industry by the operators to assure that, the deviation of the machine tool is within the tolerance value. Therefore, it has some advantages as well as disadvantages too. In the below section, the advantages and disadvantages are discussed;

Advantages

  • Unskilled employees can also use the Dial indicator as it is very easy to use and its working principle is also very easy.
  • Uniform contact pressure can be achieved by using a dial indicator.
  • Apart from that, the contact pressure is also very low due to which the mechanical component does not get any sort of impact.
  • Dial indicators cannot be affected due to temperature change or wear and tear of the gauge.
  • One of the most effective comparators in regards to mass production.
  • Minute variation can be detected by the Dial indicator.
  • The precision of this measurement device is very accurate as well as it is very economical too.
  • The versatility of this instrument provokes users to measure the deviation with this device.
  • The mechanical components can be measured very quickly.
  • Along with that, it is portable too.

Disadvantages

In the previous section, several advantages are discussed about the Dial indicator. Therefore, in this section, the crucial disadvantages of this measurement tool are discussed briefly.

  • A significant and noticeable error can be figured out by the operator due to wear and tear of the plunger and bearings.
  • In relation to gears, it has some backlash. Hence, the Dial indicator cannot be isolated from this issue. Thus, oftentimes error can be found out by operators due to backlash problems.
  • Due to the perpendicular movement of the plunger sometimes it moves inside tremendously due to which the contact pressure rise. As a result, error takes place within the device.

Application

As stated earlier, it is used to measure variation within two components. Hence, the major applications of Dial indicator are given below;

  • Geometrical errors can be found out by operators such as ovality, taper, and roundness
  • Positional errors are also can be measured by this device such as alignment problem, parallelism.
  • Deformation in relation to tension as well as the compression can be measured through dial indicator.
  • Differences between two hights, one is standard and another one is the measurement component is to find out with the help of the Dial indicator. 

Apart from the, above uses of Dial indicators, some other real-life uses of this tool are,

  • The precision level of the milling arbours.
  • Parallelism present within the ram of a shaped machine.
Source:

This article was originally written by Saswata Baksi, from Learn Mechanical


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