 I welcome you all for today's lecture that is module 2 and lecture 2. In this lecture we will be discussing about the combination set the Vernier-Kaliper. The combination set is mostly used by machinists in the workshop for various purposes. So, we will study the construction part of the combination set and what are the various uses of combination set. Then we will move to Vernier-Kaliper and we will learn the construction and various parts of the Vernier-Kaliper and then how to use the Vernier-Kaliper for inside diameter measurement and then ED measurement and woody measurement, outside dimension measurement and then we will see what are the various types of Vernier-Kaliper's available. Then we will move to height cage we will study the construction of the height cage and various applications of height cage and then what are the various types available that also we will study. Now, first let us study about study the combination set. Now, the figure shows a combination set wherein we have this steel rule and we can observe that at the center we have a groove. I can see that both edges on both edges we have scale one side it is in English system and on the other side it is in metric system and three units are mounted on the steel rule. So, this is called center head you can see there is a screw for clamping this center head to the steel rule and then we have protractor head. So, you can see the protractor fixed to the head and then again at the center there is a screw to for the clamping purpose. We can always rotate this part and we have to insert the workpiece between the steel rule and this surface. So, that we can directly get the angles and then the third part is square head this is used to check squareness of the workpieces and an angle of 45 degree and then a spirit level is also provided for checking the leveling of surfaces and then there is a scriber which can be used for scribing lines on workpiece and again there is a screw for clamping purpose. Now, let us start how to use a square head now here we can clearly see the groove provided on the steel rule for guiding the square head and then we can see the checking of a workpiece. Now, this is the workpiece for which we need to check the squareness that is whether this surface is perpendicular to the bottom surface that we need to check for that we can use the square head as shown here. Now, we have to butt the vertical surface of the square head with this vertical surface of the workpiece and then we should try to insert paper if it enters it indicates that there is some error in the squareness if it does not enter then it indicates that the squareness is ok. So, if you want any gap measurement then we can instead of paper we can always use thickness gauge which has various leaves of different thicknesses. So, by selecting the proper leaf and if we try to insert that leaf if it enters then a dimension is mentioned on that particular leaf. So, if 0.01 mm leaf enters here that indicates that the error at this over this height is 0.01 mm and then this shows the square head with the scriber and there is a space provided for inserting the scriber. Now, we will see the center head this is the steel rule with the groove and you can see on the this side we have metric graduations no I am sorry this side we have English graduations and here we have metric graduations. Now, this center head you can see the angle between these two surfaces is 90 degree. So, with respect to this blade edge this angle will be 45 degree and again this angle will be 45 degree you can see that there is a groove provided in the center head for inserting the steel rule. Now, how to use the center head this is used to find centers of cylindrical objects. So, we have a cylindrical object here and we have to place the two legs of the center head as shown here one leg should touch the workpiece here and the other leg will be touching the other side of the workpiece which we cannot see here. And now, we have to take the scriber provided in the combination set and then we have to scribe a line by taking the edge of the steel rule as a reference we can always draw a line we can scribe a line. And then we have to rotate the workpiece and again we have to draw one more we have to scribe one more line. So, intersection of those two lines will give the center point of the workpiece. So, that we can see here we have a line scribe on the workpiece surface and we have another line scribe on the top surface of the workpiece the intersection gives the center of the round workpiece. Now, let us study how to use square head with steel rule to measure the height of the workpieces. Now, we can see the square head is placed as shown here and the steel rule is vertical. Now, this reading at this edge the reading of the steel rule is 610 millimeter. So, this becomes the reference point and then we have to read the steel rule and we should note down what is the reading here. So, this becomes the measurement point the difference between this reading and the reference point reading gives the height of the workpiece. Now, we can see the reading at the top surface of the workpiece is where to read from the top 470, 475, 480, 481, 482 millimeter. So, the difference is 610 minus 482 is equal to 128 millimeter that means the workpiece height is 128 millimeter. So, the resolution available in this steel rule is 1 millimeter. So, we get reading in terms of millimeters up to a resolution of 1 millimeter. Now, let us study the measurement of angles using the protractor head. Now, I am trying to measure the angle between this surface and this surface of the square head. Now, we can see one surface of the square head is in contact with the steel rule and the other surface is in contact with the protractor head surface like this. Now, we can directly read the angle between this edge and this edge this is the angle. So, that we can directly get without any calculation using this protractor. So, the reading how to read the protractor I have shown here I can see here this is 0 degree, 10 degree, 20, 30, 40, 45 this is the reference line. So, this angle is 45 degree. So, 180 minus 45 gives this angle that is 180, 170, 160, 150, 140, 135 degree. So, 135 degree is the angle between this edge and this edge. Now, let us start the discussion on Vernier caliper. Now, we can see here we have a steel rule and we have a outside caliper. So, outside caliper does not have its own graduated scale. So, we always use outside caliper along with the steel rule. So, one leg will be gives the reference point and another leg gives the measurement point and then we have to transfer this distance over this steel rule to get the dimension of the workpiece. Now, this is this Vernier caliper is a combination of these two in the sense we have two measuring jaws. So, one corresponding to this leg the other one corresponding to this leg. Now, let me show a Vernier caliper. Now, this is the main part of the Vernier caliper this is called beam. Now, on the beam we can see on the lower side we have graduations in the metric system on the upper side of the beam we have graduations in English system to the beam a jaw is fixed. So, this is called fixed jaw and this portion is measuring head measuring head accommodates the Vernier scales. So, this side it the Vernier is in the inch system and here the Vernier is in the metric system. Now, to the measuring head a jaw is fixed. So, when we move the moving measuring head along with that this moving jaw will also move these are the measuring surfaces. So, this is the measuring surface of the moving jaw and this side we have the measuring surface of the jaw a knurled knob is provided. So, that we can put our thumb here and then we can move the measuring head at any desired location we can clamp the measuring head with the beam by tightening this screw. So, these two jaws are used for measuring outside dimensions and these two jaws are used for measuring inside dimensions. Guiding surfaces of the Vernier caliper you can see here this is one guiding surface this is another guiding surface. So, on these ground finely ground guide this measuring head will move. Now, before using the Vernier caliper it is very important to check that whether there is any clearance between the beam and the measuring head. Now, if there is any clearance if there is any movement if there is any clearance between the measuring head and the beam we can see here a wear block is provided inside. So, we have to operate these two screws and then that slackness can be eliminated and then we can use measuring instrument. Now, we can see the measuring surface it is very important that this measuring surface and the other measuring surface should have proper flatness they are finely ground and lapped to maintain very good accuracy of flatness a flatness of 1 micron or lesser than that is maintained and another very important thing is this measuring surface and this measuring surface should be parallel to each other and a parallelism of 1 micron or lesser than that is maintained. Now, we can see the main scale and Vernier scale clearly the main scale is having the resolution of 1 millimeter. Now, when we take the reading for example, I want the distance between this surface and this surface. Now, we can read first we have to read the main scale. So, main scale reading is 10 millimeter, 11 millimeter, 12, 13, 14, 15. Now, you can see 0 this reference line is crashing 15th gradation that means 0 line on the Vernier has crossed 15 15th division. So, main scale reading is 15 millimeter and then we should look for the coinciding division. Now, we can see that the gradation mark 9 is coinciding with the gradation mark 6 on the main scale that means this gradation 9 means 9 into 45 totally 45 gradations are there up to 9. So, 45 into the resolution that means 0.02 millimeter is equal to 0.9 millimeter. So, this 0.9 millimeter we have to add to the main scale reading. So, main scale reading is 15 millimeter and Vernier reading is 0.9 millimeter. So, total is 15.9 millimeter. So, that is the distance between the these two measuring surfaces. So, this is how we should take the readings. Now, let me show how an external dimension can be measured using Vernier caliper. I have taken a round part the outside diameter of which I have to measure. So, we have to hold the workpiece between the two jaws and then we have to slowly move the jaws closer to the workpiece. We should never use the ends of the jaws we should always try to use the center portion of the jaws. Now, I am moving the jaw. Now, the moving jaw has come in contact with the workpiece. Now, I can clamp the measuring head now I have to remove the Vernier caliper from the workpiece. Now, I can read the scale. Now, we can see we have the 0th line here it is just crossing the fifth graduation on the main scale. That means, this from 0 to 5 it is 50 millimeter. That means, 50 millimeter is the main scale reading. Now, I have to look for the coinciding division. We can see that this graduation marked with 4 is coinciding with the graduation marked 7 on the main scale. That means, from 0 to 4 20 divisions are there. So, the resolution of this is 0.02 into 20 divisions that gives 0.4 millimeter. So, we have to add 0.4 millimeter to the main scale reading then we get the outside diameter of the workpiece that is 50 plus 0.4 is equal to 50.4 millimeter is the outside diameter of the workpiece. Now, let me show how the inside diameter can be measured using the Vernier caliper. We have to use the jaws meant for inside measurement. Now, I am inserting the workpiece over the jaws and we have to take care that the two jaws meet the workpiece at the diameter not at any other chord. So, now, we can take the reading. The reference line that is 0th line on the Vernier is coinciding with graduation marked 2 on the main scale. So, the inside diameter of the workpiece is equal to 20 millimeter. Now, we can see here the both the jaws are in contact and we have 0 on the Vernier. It is coinciding with 0 on the main scale. So, when this happens it indicates that there is no 0 error in the instrument. And now, we can observe the main scale. So, main scale graduations we can clearly see this is the range of this instrument is 0 to 150 millimeter with the resolution of the main scale is 1 millimeter. Now, we have to get more accuracy the Vernier principle is used in this instrument. Now, we can observe that 0 to 49th reading of the main scale is taken and that is divided into 50 graduations. That means, the resolution of this instrument is 1 upon 50 millimeter that is equal to 0.02 millimeter. That means, each graduation distance between these two any two graduations on the Vernier represents a moment of 0.02 millimeter. Now, we will see what are the variations available in the Vernier caliper. Now, the photograph here shows a dial caliper instead of Vernier. See in the Vernier what happens is we have to see the which graduation on the Vernier is coinciding with the a graduation on the main scale. So, it will take some time for reading and the some effort is required to search that coinciding division. So, that can be eliminated by using the dial caliper. You can see here instead of Vernier again we have the main scale with graduations the resolution of the main scale is 1 millimeter the range of this instrument is 0 to 150 millimeter. See all the parts of the Vernier caliper they are made out of stainless steel. So, that they are not corroded and they are properly hardened and stabilized. So, that internal stresses are relieved. Now, you can see in the place of Vernier we have a dial indicator again we have a knurled knob for moving the moving jaw. So, again this can be used for outside measurement as well as inside measurement and one more thing we can observe here we have a depth bar. So, when we move the moving jaw the depth bar also will move out using this moving depth bar and the edge of this beam as reference we can always measure depth of the work pieces or depth of some blind holes. So, such things can be measured. Now, we can see a close view of dial caliper. The main scale resolution is 1 millimeter and we can observe this dial caliper wherein the resolution of this dial is 0.02 mm that means the distance between these two any two graduations indicates 0.02 millimeter that means from if the pointer moves from this graduation to this graduation it will be 0.1 millimeter and then for one complete revolution 0.1 millimeter 0.2 millimeter like this this is 1 millimeter. So, if the pointer moves from 0 to this 0 it will be 1 millimeter again when the pointer moves from this 0 to this 0 again it is 1 millimeter that means the work pieces can be measured to an accuracy of 0.02 millimeter. Now, we have a digital varnier caliper we can see here instead of dial or varnier we have a digital display. We have a digital display here and again screw is provided for clamping the measuring head to the beam at any desired location. There is a knurled knob for moving the measuring head. Now, we can see how this senses the movement. So, below inside of this beam we have a capacitive sensor and over that there is a protective coating which has a main scale. So, when the jaw moves moving jaw moves the distance mode is sensed by using the capacitive sensor again we can see the depth bar here. Now, this is the close view of the digital display of the digital varnier caliper we can see there are two buttons. So, this one is for switching between inch system and millimeters this can be used for measurement in both units inch units as well as in millimeter unit and this button is provided for starting the measurement or switching of the measuring head and provision is there for data transfer to the microprocessor the cable is provided for. So, that the measurements can be transferred to a computer for statistical control analysis. Now, there are other kinds of calipers varnier calipers you can see here coolant proof digital caliper. Sometimes what happens the operator is running the machine is machining some component and then some coolant is continuously applied on the machining zone. Now, during that time whenever he wants to measure the diameter he stops the machine and then he takes the caliper and he tries to measure the diameter of the workpiece or if it is milling he checks he wants to measure the diameter of the length of the workpiece during that time the coolant may splash on the instrument. So, it may damage the instrument. So, recently the coolant proof calipers are developed even if the coolant splashes on the instrument digital caliper nothing will happen. So, the proper gaskets are provided and leak proof arrangement is provided and they are also tested in the pressurized chambers to check whether they are really coolant proof or not. Now, we have extra long jaw caliper again you can see the beam the beam construction remains same only thing is there is difference in the jaw length. So, these are extra long jaws for example, sometimes the workpiece will be having some features like this I am just drawing a sketch of a workpiece which is having some internal feature now with the normal one year caliper or dial caliper it becomes difficult to measure this distance because of this depth involved. Now, we can always have an extra long jaw caliper. So, that these two jaws will enter into the workpiece and then they can measure the distance D. Now, this length of jaw will be up to 300 millimeter long jaws are available. Similarly, see this is extra long jaw caliper similar to this we can have extra long vernier caliper jaw remains the normal length whereas, the beam length beam length will vary up to 3 meters. So, such a long calipers one can get. So, they are required to measure big workpieces and then we have a point caliper we can observe the measuring jaw ends they are pointed. So, these things will be useful for measuring difficult to assess places for example, see we have a workpiece like this. So, very narrow grooves we have now I want to measure the distance between these two. So, this distance I want to measure. So, normal caliper cannot be used here because of the size of the jaw. So, this pointed caliper point end calipers can be used in such applications. Now, there are digital calipers with special attachments you can see here we have a normal measuring jaw here, but with special attachments different kinds of attachments are possible. So, such attachments will be useful depending upon the application for example, here we have flat surface and here it is pointed. So, if you have a workpiece like this now if we use both flat tips then what happens is the contact will be like this. So, here there will be gap. So, this will lead to some error in the measurement. So, it is necessary that a point contact here there is point contact because the one jaw or one anvil is flat and it makes a point contact here and then since this is pointed. So, it will make a point contact and that it will go and touch the workpiece. So, we get the correct measurement. Similarly, we can have center distance varnier caliper we have the main beam with finer adjustment screw and then you can see the jaws have special shapes special contour they are contoured type or cone type cone type jaws are there and then other interesting thing is this moving jaw will move horizontally and this jaw will move vertically. You can see there is a screw for clamping this jaw at any desired location we can unscrew this we can move this jaw along with the scale and then at any desired location we can clamp it. Now, what is the application of this center distance varnier caliper let us draw a simple sketch. Now, say we have workpiece like this we have a hole here and then we have another hole here. Now, I want to know the center distance between these 2 holes. Now, since the 2 holes they are not in the same planes they are this different planes. So, we cannot use ordinary center distance varnier caliper. So, in that case this special center distance varnier caliper will be of grateful it will be very useful. So, this cone will go here and then this cone can be moved and then it will enter here like this and then we can read the center distance. Now, we can see other types of calipers. So, this is a digital caliper this is offset caliper. Now, you can see this is the moving jaw and this is the jaw which is beam mounted jaw. So, it is mounted on the beam and then it can be moved in the vertical direction and it can be clamped at any desired location using this screw. Now, what is the use of such a offset caliper? Now, I can see here we have a stepped work piece. We have a stepped work piece or we have a step here I want to measure the distance between this surface and this surface. Since this surface and this surface they are not at the same level. So, we cannot use the ordinary caliper. So, in such cases this offset caliper will be useful we can move this beam mounted jaw. So, that it will be in contact with this vertical surface and this jaw will be in contact with this vertical surface and then we can directly read what is the distance. Now, we can always have a variation of jaws. So, in this case we have a radius the jaws we can observe the jaw the jaws have a shape they are radius. So, such radius jaws will be very useful when we want to measure the internal diameter of the holes accurately. So, say when we use the radius jaws the contact will be proper point contact will be there and we get the correct measurement of the internal dimension. So, if we use flat jaws to measure internal dimension of this type what happens is you can see here the contact is at these two points not at the center. So, this much error will be they get entered the error gets entered or error gets creep in. So, we do not get the correct inside dimension. Now, we have offset center distance caliper. So, we have a workpiece like this we have a hole here and we have another hole here I want to get the center distance between these two in such cases offset center distance caliper will be very useful. Now, if we have another kind of arrangement in the calipers I can see here the jaws are provided on the bottom of the caliper and one jaw is having a flat surface and another jaw is conical. Now, I can see the front view here this is the jaw having flat surface flat measuring surface and here we have a cone shaped jaw. Now, what is the use of such a such an arrangement? Now, when we have a workpiece like this there is a hole here I want to know the distance of center of hole with reference to this vertical surface. So, in such cases we can measure the edge to center distance edge to center distance using this type of edge to center caliper. So, this jaw will come in contact with this vertical surface of the workpiece and then cone will enter into the hole and we can directly read this distance and there is another variation of caliper. So, that is blade type jaw the caliper will be having blade type jaw you can see the blade type jaw from the end view we can see the thickness of the blade is 0.75 millimeter. So, what is the use of such an arrangement? So, this will be very useful when we wish to measure very narrow grooves. Now, let us conclude this session in this session we studied about very important instruments that is combination set and then Bernier caliper. We studied about construction of these instruments and how to use those instruments for various applications and what are the variations viable. So, those things we studied in the next class we will continue the linear measurements. Thank you.