What Is Dial Gauge?
Dial gauges are used to measure the flatness and inclination of objects. It is used to check round bar roundness. It checks the flatness of an object as compared to the flatness of the standard object. In the mechanical field, dial gauges are used to check the flatness and alignment of various jobs and workpieces.
It very easy’s to use as compared to other devices like Vernier calipers, micrometers, etc.This dial gauge is based on the principles of “rack and pinion.” The dial gauge can measure up to a minimum of 0.01 mm readings. Therefore its lowest count is 0.01 mm.
Parts of Dial Gauge Indicator:
There is a metal casing which is the outermost part of the dial gauge.
#2. Graduated Scale
Inside the casing, graduated scales are present, marking various readings.
A Pointer exists that indicates the measured value on the graduated scale.
#4. Small Dial Gauge
This small dial gauge is present insides the dial gauge. It also has graduation. This small dial gauge has reverse reading. The readings of small dial gauges can be straight or reverse depending on the mechanism used in the gear train for the movements of the pointer to the small dial gauge.
#5. Small dial pointer
There is a small indicator that points to the measured value at the graduation of the small dial indicator. It is also called a shorthand indicator.
The plunger or spindle moves up & down inside this stem.
#7. Contact Point
This contact point will have contacts with the surface & will help in the motion of the plunger. When the pointer of the external pointer completes its revolution, the pointer of the smaller pointer wills move from 0 to 1, i.e., the smaller dial pointer will show 1 mm when this larger pointer will exceed 100 reading in the larger dial pointer.
When the external pointer completes its ten rotations, the pointer of the smaller indicator will return to zero. The small dial gauges are very helpful in taking a reading.
The Internal Arrangement of Dial Gauge:
In the internal part of the dials gauge, there is a rod, & in this rod, there is a rack cut on this rod. This rack is connected to a smalls gear S1, & this small gear S1 is attached to the big gear G0, & both have the same axis.
This small pinion is also connected to another’s big gear, G1. If the small gear S1 takes ten rotations, then the big gear G1, which is connected to the small gear S1, will complete one rotation in the opposite direction.
Now, this bigs gear G1 is also connected to another’s small gear, S2, which is the gear of the outer dial pointer, & this small gear S2 is attached to a big gear G2, & both have the same axis. Thises big gear G2 is connected to a helical spring.
The main function of the helical springs is that it stores the rotational energy of the gears when the gears rotate.
These helical springs are used to reset the positions of the gear & the pointers. When the measurements are completed, the helical spring transfers the stored energy to the connected gear, & all the gears move in the reverse directions one by one & reach their initial position. Also, the rod moves to its initial positions.
Working of Internal Parts:
When the dial gauge is placed on top of a workpiece, the dial gauge rod moves upward, and the racks cut on it also move. The small gear S1 that attaches to the rack on the rod starts rotating. When the rod moves upward, the small gear will rotate clockwise.
This smalls gear S1 is connected to a large gear G1. This larger gear controls the G1 pointer P2, which is a pointer to the smaller dial gauge. When the smaller gear S1 rotates clockwise, the larger gear G1 will rotate in the anti-clockwise direction, and the pointer P2 connected to the larger gear G1 will rotate in the anti-clockwise direction.
G1 as this big gear An anti-clockwise direction will rotate, then the outer gear’s small gear S2 will rotate clockwise, and so the outer dial P1‘s pointer will rotate in the clockwise direction. In addition, the larger gear G2 will also rotate in a clockwise response.
Now this larger gear is connected to the G2 helical spring, and the helical spring will rotate in an anti-clockwise direction and accumulate rotational energy; and when the work is completed, the helical spring will give its energy backs to the gear, and the gears and pointers to their initial position Will come back As all gears will move in the opposite direction. So the racked rod will also move upward and return to its initial position.
Least count of Dial Gauge Indicators:-
100 lines reading in outers scale = 1mm = 1 full rotations on outer scale
Therefore, least count = 1 rotation on main scale / No of the division moved on the dial scale.
1 Rotation On Main Scale = 1mm
No. of the division moved on dial scales = 100
Hence, Least Count = 1mm /100 = 0.01mm.
How to Take a Reading on Dial Gauges:
Suppose we use a dial gauge to measure the flatness of the workpiece. When we use a dial gauge to measure the flatness of the workpiece, it shows some variation. The small dial gauge indicates a reading of slightly more than three (3).
First, we will focus on the reading of the small dial indicators. We will take the only completes the reading of the small indicator. So, if reading is slightly more than three, then we will only read three and ignore the rest.
When the larger dial pointer completes a full rotation, the smaller dial pointer will move a unit that is equal to 1 mm. After taking the readings of the small dial indicator, the readings of the external dial are taken. Explain that the external dial indicator has a reading of 42.
After reading both the indicators we calculate the variations in mm using this formula:
Formula for variations (in mm) = short dial reading + (external dial reading x least count)
Now we have to assume,
Variation = 3 + (42 x 0.01)
= 3.42 mm
This is an accurate reading of surface variation using a 3.42 mm dial gauge indicator.
Types of Dial Indicators:
Types of Dial Indicators Many different types of dial indicators exist, differentiated by factors such as their size, connection method, & the type of information on their faces.
- Balanced reading dial indicator.
- Continuous Dial Indicators.
- Reversed Balanced Dial Indicators.
- Reversed Continuous Dial Indicators.
- Plunger Dial Indicator.
- Lever Dial Indicator.
#1. Balanced Reading Dial Indicators
Balanced reading dial indicators are named in such a way that the information on the face of the dial is organized. Figures are printed on the face of this dial running in two directions starting from a zero in the center. Often, positive numbers are depicted to the right of zero and negative numbers to the left.
#2. Continuous Dial Indicator
The constant number dial indicator does not have two sets of numbers depicted on the balanced reading dial indicator. On this type of dial indicator, the figures move in one direction without pauses and without any separation.
#3. Reversed Balanced Dial Indicators
Reversed Balanced Dial Indicator is named because they have the same basic positive & negative scales on each side of a zero, but positive numbers are on the left and negative are on the right.
#4. Reversed Continuous Dial Indicators
Reversed Continuous, or Counter-Clockwise, Dial Indicators are similar to Continuous Dial Indicators except that the number moves in the opposite direction.
#5. Plunger Dial Indicator
The Plunger Dial Indicator also has a clock-like face but features the rider on one of their sides. A common use for plunger dial indicators is to measure the work of injection molding machines. The mechanism that allows this type of dial indicator to work is a rack and pinion, which changes the linear thrust of the rider in rotary motion for the dial.
#6. Lever Dial Indicator
The specialty of lever dial indicators is their lever and scroll mechanisms, which cause the stylus to move. These types of dial indicators are more compact and easier to use than plunger-type dial indicators and are therefore often used.
Applications of Dial Gauge:
- I am comparing two heights or distances between narrow limits.
- To determine the errors in the geometrics form, such as ovality, roundness, and taper.
- For taking accurate measurements of deformations such as intension and compression.
- To determine position errors of surface such as parallelisms, squareness, & alignment.
- To check the alignments of lathe centers by using a suitable, accurate bar betweens the centers.
- To check the trueness of milling machines arbors & to check the parallelism of shaper arm with table surface or vice.
Advantages of Dial Gauge:
- The size of the dial gauge is very small & compact, so it can be used easily in mass production.
- Dial gauges can be used to measures the amounts of tappers in round objects easily.
- It is the most flawless tool in takings linear measurements.
Disadvantages of Dial Gauge:
- The precision of the dial gauges is often lost due to the vibration of machinery.
- The main disadvantage of the dial gauges is parallax error. ( Parallax error: Parallax error occurs when the measurements of an object’s lengths are more or less than the true lengths because of your eye being positioned at an angle to the measurement’s markings. )
- Due to space constraints, the tools are needed to be installed at an angle, due to which the accuracy of the devices is lost.