DETAIL STUDY OF MEASURING TOOLS
Measuring Tool-Vernier Caliper,Micrometer,Vernier Bevel
- Vernier calipers
- OBJECT: To determine the radius of a cylinder using Vernier calipers
Apparatus used: Cylinder, Vernier calipers.
Formula: Radius =diameter/2 or r=D/2
Theory – Vernier calipers- It is a device to measure the length or width of any small object with greater precision than with a normal cm scale. While the least count of a cm scale is one mm. The least count of Vernier calipers is normally 0.1 mm or even lesser. Different Vernier calipers have different least counts.
Vernier calipers consist of a rectangular steel bar graduated in inches on one side and centi meters on the other side. This is known as the main scale. Over this scale, another small scale slides called Vernier scale . The instrument has two jaws A and B. The jaw A is fixed at the end of the main scale, while the jaw B is movable. It is a part of the sliding Vernier scale. Each jaw is at right angles to the main scale. Usually when the two jaws are touching each other, the zero of the Vernier scale coincides with the zero of the main scale. If it is not so then the
instrument has a zero error. It has also the jaws protrude upwards as P and Q. These projecting jaws are used to measure the internal diameter of the tubes. The movable jaw also carries a thin rectangular rod R that is used to measure the depth of.
Parts of Vernier Caliper:
A Vernier Caliper has following parts:
- Outside jaws: It used to measure the external dimension of objects.
- Inside jaws: It used to measure the Internal dimension of objects.
- Measuring Depth Probe: It is used to measure the depth of objects.
- Main Scale (cm).
- Main Scale (inch).
- Vernier Scale (cm).
- Vernier Scale (inch).
- Retainer: It used to block the movable part.
Working Principle of Vernier Caliper:
The Vernier Caliper is a Precision Measuring Instrument which is used to measure length, depth, diameter of the given specimen
Working Principle of Vernier Caliper:
The Vernier Caliper is a Precision Measuring Instrument which is used to measure length, depth, diameter of the given specimen.
The detailed explanation of Vernier Caliper is as follows.
Calipers are nothing but the Jaws which are used to fix the given component.It consists of two jaws and those are Upper Jaw and the Lower Jaw.Upper Jaws are used to measure the Inner diameter of the given specimen whereas Lower jaws are used to measure the outer diameter of the given specimen.It consists of two scales. One is the Main Scale and the other is the Vernier Scale. Both these scales are measured in Inches as well as in millimeters. The locking pin is used to tighten the jaws at the given measurement.How to Measure the Depth of the given specimen?
The measuring depth probe is used to measure the depth of the given specimen.
- To check any Measurement?
In order to calculate the dimensions, the given specimen is to be placed between the two jaws. One is a fixed jaw and the other is a movable jaw.The object is to be placed in between the two jaws and is fixed by means of locking pin.
Procedure:
A. Least count of Vernier calipers or Vernier constant: First of all find out the least count of Vernier calipers. The
least count of Vernier can be determined by two methods.
method 1:
1. Find out the value of one division of main scale.
2. See how many division of main scale is equivalent to Vernier scale divisions.
3. The difference between one main scale division and one Vernier division is called Vernier constant or least count
of the Vernier calipers.
Vernier constant=least count of Vernier calipers= 1 M.S.D- 1V.D
Example: Let the value of one division on main scale is equal to 1mm and the 9 main scale divisions is equivalent to 10 Vernier scale
divisions.
1 V.D = 9/10 M.S.D
Least count of Vernier calipers= 1 M.S.D- 1V.D = 1/10 M.S.D = 0.1 M.S.D = 0.1 mm=0.01cm
method 2:
1. Find out the value of one division of main scale.
2. Find out the total number of divisions on Vernier scale.
3. The ratio of value of one division of main scale and total number of divisions on Vernier scale is called as Vernier
constant or least count of the Vernier calipers.
Vernier constants=least count of Vernier calipers= number of divisions on Vernier scale
value of one division of main scale
Formula of Vernier Caliper:
The formula of Vernier calipers was shown below.
Measurement= M.S.R + (V.S.R*L.C)
Least Count of Vernier Caliper:
The least count was calculated as follows.
Least Count (L.C)= 1 MSD – 1VSD
How to Read Vernier Caliper in mm?
By knowing the readings of Main Scale Divisons, Vernier Scale Divisons and Least Count, the reading of a specimen can be found and it can be theoretically calculated as follows.
Calculation of Main Scale Division:
If the zeroth division of the vernier scale is coincided with (some number) on the Main scale(consider it as 10) then 10mm is the Main scale Reading(M.S.R).
M.S.R = 10mm.
Calculation of Vernier Scale Division:
After that, you need to check which division on the vernier is exactly coinciding with the main scale as shown in the fig.
vernier calipers-least count
If you see in the figure,10th division in the vernier scale is exactly coinciding with a division on the Main scale. Therefore you need to count the no.of divisions from 0-10.The no.of divisions from (0-1) on a vernier scale is 5 divisions.Therefore,upto (0-10),it is 50 divisons. So,take the Vernier Scale Divison is 50.
V.S.R=50.
Calculation of Least Count:
As we know the formula of Least Count (L.C)= 1 MSD – 1VSD
1 VSD= (49/50) MSD= 0.98 MSD
Substitute the above value in the formula of Least Count (L.C)= 1 MSD – 1VSD
Therefore,
Least Count (L.C) =1 MSD – 0.98 MSD= 0.02 mm
Therefore, the Least Count of Vernier Caliper is 0.02 mm.
Measurement= M.S.R + (V.S.R*L.C) = 10+ (50*0.02) = 10+1 = 11mm
Therefore, the reading on Vernier Caliper is 11 mm.
Vernier caliper scale with the normal 0.02 vernier constant, showing measurement of object at 19.44 mm to two decimal places
Here is a Video on How You Can Measure on Vernier Caliper:
Range of Vernier Caliper:
The range of a vernier caliper is the difference between the largest value and the smallest value that a caliper can measure and It is equivalent to the length of the main scale.
Mostly, vernier calipers have a range of 6 inches i.e. 300mm.
Resolution of Vernier Caliper:
A Caliper’s resolution is indicated at the end of the vernier scale and it is the smallest distance that the caliper can measure.
The resolution of Vernier Caliper are:
Imperial vernier calipers is usually 0.001 in, whereas for Metric calipers is either 0.05 mm or 0.02 mm.What is the difference between a dial caliper and a Vernier caliper?
In almost all industries people were using the vernier caliper, not of dial mode and thereby there is a little chance(in terms of microns) that they will get an error.
The basic difference between the standard vernier and the Dial Vernier is as follows.
Dial Caliper or Digital Vernier: Direct Reading (Perfect Reading) will be displayed.
Standard Vernier: Manual Reading (You need to check manually).
Digital Vernier Caliper
Instrument error or Tolerance:
An Instrument error refers to how accurate a vernier caliper is.
Low tolerance measuring tools provide very accurate results with a small margin for error and Vernier calipers is one of them.
Applications of Vernier Caliper:
Some of the applications of vernier calipers are listed below:
Educational Sector Steel Industries Science Labs Aerospace Industries Medical Purposes
Advantages of Vernier Caliper:Accuracy and Precision:
They provide precise and accurate measurements over a large range.
Versatility:
It can have the ability to measure any type of dimensions of a component, for example:
It can measure the outer diameter of the given component.It can measure the Inner diameter of the given component.It can measure the depth of the given component.It can measure the length of the given component.Durability:
As the Vernier is made up of Stainless steel(Anti-Corrosive material), it can sustain for a long period of time and thereby its durability will be high.
Cost:
It is relatively less expensive compared to other calipers.
Ruler or Measuring Tapes:
If you want the accuracy, you should have to leave the rulers or measuring tapes for the measurement of any component.
Disadvantages of Vernier Caliper:Possibility of Errors:
It needs much concentration to read a dimension of the component else there is a possibility of error.
Accurate Tools:
If you are unable to use vernier calipers, then you can go for the other accurate tools present in the industry like Dial Caliper.
Magnifying Glass or Eyesight:
Good Magnifying glass is required during taking the measurement of any component if your eyesight is not proper else it results is incorrect.
Micrometer
A micrometer is an instrument used for making precise linear measurements of dimensions such as diameter, thickness, and lengths of solid bodies. It is made of a C-shaped frame with a movable jaw operated by an integral screw. The fineness of the measurement depends on the lead of the screw while the accuracy of the measurement depends on the accuracy of the screw-nut combination.
It is often misunderstood with the micrometer (μm) – the standard unit of length measurement. Another common name used for a micrometer is micrometer caliper due to its similar appearance to the caliper.
A micrometer is composed of the following parts:
- Frame – It is the C-shaped body that holds the anvil and barrel in constant relation to each other. The frame is heavy and has high thermal mass. To prevent substantial heating up, it is covered by insulating plastic.
- Anvil – The shiny part the spindle moves toward and the sample rests against.
- Barrel – Stationary round component with a linear scale on it.
- Screw – Found inside the barrel and is considered the heart of the micrometer.
- Lock nut – Component that one can tighten to hold the spindle stationary.
- Spindle – Shiny cylindrical component that causes the thimble to move toward the anvil.
- Ratchet Stop – The device on the end of the handle that limits applied pressure by slipping at a calibrated torque.
Principle of Operation
The basic principle of operation of a micrometer is as follows:
- The amount of axial movement of a screw that is made accurately can be measured by the amount of rotational movement of it.
- This is because the pitch of the screw is constant.
- The measurement made due to the rotational movement is some amplified form of the actual axial movement of the screw.
Care and Proper Use of a Micrometer
Before you rotate the thimble or the ratchet knob, unlock the locking lever. Make sure to clean the measuring faces with the help of a clean cloth before you begin taking measurements.
As you begin measuring, start rotating the ratchet knob (not the thimble). The ratchet knob will ensure you don’t overtighten the thimble, as that will not only give an erroneous reading but can damage the instrument too.
The horizontal line on the sleeve should be aligned to zero when the micrometer function is at its minimum reading. In case it does not happen, the instrument must be calibrated. For calibration, each device comes with a half-moon adjusting wrench.
Remember to use the thimble lock while the micrometer is still holding the object. If you do not do this, the spindle might move a little while taking the reading or taking the object off from the micrometer. It’s also advisable that you don’t keep the instrument exposed to the sun for long
Bevel protractor has a very vital role in mechanical architectural drawing.General use of bevel protractor is decreasing due to the introduction of software like CAD.The bevel protractor is used for testing the angles very precisely.It is used for a variety of mechanical and engineering related applications.
Construction of Vernier Bevel Protractor
Vernier Bevel protractor consist of the following components.
- Main body
- Base plate stock
- Adjustable blade
- Circular Plate with graduated vernier scale divisions.
- Acute angle attachment
The following figure shows the vernier bevel protractor
http://www.textillearn.com
- The base plate(Stock) consisting of the Working edge will be mounted on the Main body.
- And the Acute angle attachment is also mounted on the main body.
- This acute angle attachment can be readily attachable/detachable with the Locking Nut.
- A circular plate having a vernier scale in it, also mounted on the Main body frame.
- This circular plate is carrying an adjustable blade which can travel along its length and locked at any position with the help of the blade locking nut.
- The adjustable Blade one end is bevel at angles 45° and the other end is bevelled at 60°.
- This Main body frame itself having a graduated scale called the main scale.
- The circular plate can rotate freely on the main body.
- There is a slow-motion device which helps to control the rotation of the circular plate on the main body
1. As the Base Plate (Stock) acts as one of the working edges, and the other working edge will be the blade which is held on the circular plate. as you can see the some of the sample positions of the Vernier bevel protractor in action.
2. This Adjustment Blade can be rotated along with the circular plate on the main body.
3. Which means the vernier scale on the circular plate will be rotated on the Main scale which is graduated on the Main body.
4. The Vernier scale has 12 divisions on each side of the centre zero. (It means there are 24 divisions on the vernier scale)
5. The 12 divisions are denoted as 60 min on the vernier scale (Like this 15, 30, 45, 60). That means 12 division = 60 minutes
6. One devision= 60/12 = 5 minutes.
7. On the Main scale, the same portion is represented as 23° (12 divisions on vernier scale = 23° on the main scale )
8. One division on the Vernier scale = 1.91666° = 1° 55′ (one degree 55 minutes).
9. As similar to the vernier caliper working principle as Zero on the vernier scale moves on the main scale.
10. While taking a measurement, The Zero line on the vernier scale shows the reading on the main scale, called main scale reading.
11. At somewhere The divisions on the vernier scale will coincide with the divisions on the Main scale. this reading is noted as the Vernier scale reading.
12. With these values along with the least count of the Vernier bevel protractor, we can calculate the Reading.See the following example how to calculate the total reading.
Measurements with Vernier Bevel Protractor
Consider the Following is a reading of an angular measurement.
The total reading =the main scale reading + the number of the division at which it exactly coincides with any division on the main scale × least count of the vernier scale.
In the above case
The main scale reading = 10°
Vernier scale reading (the number of the division at which it exactly coincides with any division on the main scale) = 3rd division
Least count of the vernier Bevel protractor = 5 Minutes
The total reading = 10°+15 minutes = 10 + (15/60) = 10.25°
OTHER MEASURING TOOLS
Tape Measure
It’s the essential measuring tool for a reason: though small in size, it’s useful on darn near every project. I say buy them in bulk and keep one in every room of the house; you’re likely to misplace them.
Quick tip: when trying to achieve accurate measurements with a tape measure, hold the 2″ line on the edge, take your measurement, and then subtract two. This gives you a much more accurate measure than taking it from the little jiggly metal thing at zero.
2. Combination Square
This is my number one measuring multitasker when doing any kind of woodworking, art, or design project. Use the head to set 90° and 45° angles and the adjustable ruler to scribe a line over a long distance. You can find less expensive plastic combination squares for around $20, but I recommend saving up for a high-quality model, $40-100, which will last longer and provide much better accuracy.
3. Micro Rule
This might not get you very far when adding a room to your home, but if you have one around, you’ll find all kinds of uses for it. These small rulers measure in 32 ends and 64 ths, making them great tools for setting up bit and blade depths on power tools, not to mention an infinite number of little household repair jobs. I use mine all the time.
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