 Welcome back to the lecture series on metrology. Now we will start module 11 on machine tool metrology. In this lecture, we will be covering the following topics. What is the need for machine tool metrology? What are the various instruments used for conducting the alignment tests on machine tools? And what are the different alignment tests conducted on machine tools? And then we will cover some tests on lathe and some tests on drilling machine. And then we will discuss about general inspection of machine tools. Now we will start lecture number one in the module number 11. In this lecture, we will be covering the following topics. What is the need for machine tool metrology? What are the various instruments used to conduct alignment tests? And what are the different alignment tests normally conducted on the machine tools such as flatness test of tables, parallelism test, perpendicularity test etc. And then we will discuss about some specific geometrical tests conducted on engine lathe. Now let us try to understand what is the need for machine tool metrology. There is a continuous demand for highly accurately machined components because of this considerable research in machine tool design has been carried out and machine tools are being built up with high geometric accuracy. A distinct field of metrology has matured which is concerned primarily with the geometric tests of the alignment accuracy of machine tools under static conditions. And there is a need for conducting the alignment accuracy test when the machine tool is being loaded that is when the machining is being carried out whether the alignment is proper or not. So for that practical tests are being conducted. Now in order to ascertain the condition or performance of the machine tool, inspection charts have been developed by standards organization. These charts will enable the manufacturer or inspector to check the various alignments of machine tools against prescribed limits. Alignment tests check the relationship between various elements of the machine tool such as forms and positions of machine tool parts and displacement relative to one another when the machine tool is unloaded. For example, whether the positioning of the type stock with respect to the spindle axis is proper or not. Whether the saddle movement is parallel to the lathe axis is okay. Whether the movement of the tool slide is parallel to the spindle axis. What is the perpendicularity of movement of the cross slide with respect to the lathe axis such things are checked during the alignment test. Now let us discuss the various instruments used to conduct acceptance tests on machine tools, alignment tests on machine tools. The very first instrument is the dial gauge. I should have a minimum measuring pressure. It should not exert too much of pressure on the machine tool part. The measuring the pressure range should be between 200 to 100 grams. The graduations on the dial must be very much clear and accurate to 0.01 millimeter. We can observe a dial indicator with the least count of 0.01 millimeter and range of 0 to 10 millimeter. The dial gauge must be fixed to robust and stiff bases in order to avoid displacements due to shock or vibration. Magnetic stands are normally used for mounting the dial indicator on the machine tool parts. Test mandrel is a very important instrument used while conducting the alignment test. These are used to check the true running of spindle and to check whether the movement of slide is parallel to the axis and to check the these test mandrels are normally made of steel. They are hardened, stress relieved and ground and they are made to a length from 100 to 300 millimeter. The quality of the mandrel especially the straightness and the roundness of the mandrel is very very important in order to get accurate results. Two types of test mandrels are used. The first one is the mandrel with cylindrical surface and a tapered shank. You can see here this is this portion is cylindrical and at the end there is a tapered shank which will go into the tapered bore of the main spindle. Other type is a cylindrical mandrel that can be held between the centers. You can see the centers are provided on both ends of the cylindrical mandrel to fix the cylindrical mandrel between the sectors. Now another important instrument is straight edge. So these are normally made of cast iron or steel. You can see a view of straight edge. These should be heavy, well ribbed and free of internal stresses. The two surfaces, the top surface and the bottom surface surfaces should be parallel to each other. Another important instrument is standard square. The standard square must have a wider bearing surface. The error at the top should be less than plus or minus 0.01 millimeter. So when we move the dial indicator from bottom to the top at the end at the top end the error should be less than plus or minus 0.01 millimeter and for a precision square the error at the top should be less than plus minus 0.005 millimeter. Now spirit levels are also used while conducting alignment test on machine tools to check the flatness of bases and tables and to check the straightness of guideways. So these are used in the shape of a bubble tube which is mounted on a cast iron base. We can see a view of spirit level. Two main types are used. One is horizontal type and another one is frame spirit level with a sensitivity of 0.04 to 0.06 millimeters per meter for each deflected division. Another important instrument used is autocollimatter which is used to check the deflections of long beds in horizontal vertical and thin-clined planes. We can check the deflection of guideways using the autocollimatter as shown here. Waveriness meters are used to record the surface waveriness of the beds and the tables with a magnification of 50 to 1. Work tables are checked for flatness using straight edge on spirit level. The work tables should be either flat or concave. If the table surface is convex like this, what happens is we keep the workpiece on the table and when we clamp the workpiece using the clamps, because of the clamping force the thin workpieces may deflect and they may bend like this. To avoid that, the work tables are made flat or if there is any deviation, it should be in the form of concavity. So this is checked using spirit levels and straight edges. Columns, uprights and base plates are checked for deviation from the vertical and horizontal planes. That means the columns of the machine tools, whether they are perpendicular to the base plates or not. So that is checked using dial indicators and squares. Practical tests are conducted by machining the workpieces and appropriate feeds and speed rates are used for machining and then the workpiece after machining is checked for size, form and surface finish, whether the sizes are okay or not. If there is any larger deviation from the shape and size, whether we are getting the cylindrical objects or tapered objects or a drum shaped objects. So all those things we can check by conducting practical tests. Also we can check the surface finish that is obtained using surface tester. We can refer IS-1878 part 3 and for test chart for conducting tests on blades and we can refer IS-2425 test chart for pilot and vertical drilling machine for conducting alignment test on drilling machines. Now let us discuss on the alignment tests conducted on engine lathe. We can see the picture of engine lathe. There are many sub-assemblies. So we have bed sub-assembly and then we have carriage for saddle sub-assembly and then we have the tie stock sub-assembly, head stock sub-assembly and then we have the quick change gearbox here, apron. So now during assembly we have to carry out the various alignment tests on these sub-assemblies to check whether they are aligned properly and once they are assembled we have to check whether all these sub-assemblies are aligned properly to each other, whether the movements of various sub-assemblies is parallel to the main spindle axis, whether the moment of the tie stock is parallel to the axis and then saddle movement whether it is parallel to axis. Such things we have to check and if there is any error by scraping the appropriate surfaces we can change the alignment and we can set the alignments. Now one alignment test that is before conducting any alignment test it is very essential that the leveling of the machine should be checked whether the lathe is properly leveled and installed that we have to check. We have to check leveling in both the directions, longitudinal direction as well as the transverse direction. So along the length of the bed we have to check the alignment that is longitudinal direction and perpendicular to the length of the bed we have to check the leveling in the transverse direction. Now approximately the saddle is kept at the middle of the guideways and then we have to use a precision spirit level. At various positions we have to keep the spirit level and we have to note down the reading this precision we have to repeat for both the guideways and if there is any error it should not exceed 0.01 to 0.02 mm for any length of 500 millimeters. So this is the length of the bed. Similarly alignment should be checked in the transverse direction for that we have to keep a bridge piece on the guideways and then we have to place the precision level and then we have to note down the reading. Again in the transverse direction also the error should not exceed 0.01 to 0.02 mm for any length of 500 mm. Also this experiment or this check will give whether the guideways are straight or not. So when we keep the spirit levels at various positions along the bed we have to keep the spirit level along the length of the bed at various positions and then we should note down the reading and this will indicate whether the guideway is straight or is there any deviation from straightness. If there is any deviation it should be in the convex direction only that means the guideway should be convex. The reason is because of the weight of the saddle and because of the action of cutting forces the guideway tends to become straight. So that is why initially it should be convex. If it is concave then the effect of concavity will increase with the action of the weight of saddle and cutting forces. Also another reason is if the guideway is convex because of the continuous movement of saddle the surface of the guideway will hone out and it becomes straight. Now if the leveling is not proper it may be corrected by putting the setting wedges or shim plates under the support feet of the lathe. That means we can adjust the we can insert the shim plates or wedges for leveling purpose. Now true running of locating cylinder of means spindle this test is conducted to check whether the locating cylinder is running truly or not. We can see the assembly drawing of the main spindle of a lathe. It is supported by beings at both the ends the front end and the rear end. We can see the photographic view of the assembly of the spindle the check the spindle are supported by bearings. Now we can see the locating cylinder surface here the locating cylinder surface. We can also see the rear view of the check and also the face plate. The locating cylinder is provided on the main spindle to locate the check or face plate. So this face of the check will go and fit on the locating cylinder. The locating cylinder should run without any run out. If there is any run out of locating cylinder then the check and face plate will also run without a trueness. So we don't get the proper geometry on the work pieces. Now to check the run out of the main spindle locating cylinder we have to use a dial indicator. The plunger of the dial indicator should touch the locating cylinder surface that means the plunger should touch the locating cylinder surface and we should slowly rotate the locating cylinder and then we should note down the reading of the dial indicator. For true running of the locating cylinder there should not be any reading in the dial indicator. If there is any out of running then the indicator will show the readings. In that case again we have to finish the machine. The surface of locating cylinder should be finished again and then again the true running should be checked and then finally it can be assembled into the headstock. Now we will discuss about axial slip of main spindle and true running of shoulder face of spindle nose. Again we can see the assembly of the spindle. The chuck is mounted on the spindle nose. We can see the bearings which support the main spindle. Now we can see here this is the shoulder face. This is locating cylinder and this is the shoulder face of spindle nose. The chuck will be it will come in contact the back surface of the chuck or face plate will come in contact with this shoulder face. It is essential that there should not be any axial slip of the spindle. So if there is axial slip then it is nothing but the axial movement of spindle then the chuck will also move axially and that will affect the machining accuracy particularly in case of screw cutting. And it is very essential that this shoulder face should be perpendicular to the axis. Now while measuring we have to mount the dial indicator on some fixed part of the machine and the plunger should touch the shoulder face that means the plunger should come in contact with the shoulder face and we have to take readings at two diametrically opposite positions one reading here and slowly we have to rotate the shoulder face and then second reading we have to take here. The difference will give the axial slip. Now axial slip is a movement of spindle which follows the same pattern and is due to the manufacturing error of the shoulder face. The plunger of the dial indicator rests on the face of the shoulder as shown here and the dial gauge is clamped to the bed. The locating cylinder is then rotated. So this locating cylinder is slowly rotated and two readings are taken from the dial indicator one reading here and we have to rotate it through 180 degrees and the second reading we have to take on the dial indicator. The difference will give the axial slip. The readings are taken at two diametrically opposite points. Error includes the error in bearings if there are any errors in the bearing then also there will be axial slip and the shoulder face not perpendicular to the axis. Now you can see here if this shoulder face is at some inclination like this. So then also we get when we rotate it there will be axial slip and we get the readings here and sometimes the face the shoulder face this is the locating cylinder and this is the shoulder face maybe there are some irregularities in the shoulder face because of that also we get axial slip. So particularly during the screw cutting a pitch of the screw cut will vary due to the axial slip. So it is very essential that the machining of the shoulder face is very very important a lot of care should be taken and precision machining process should be used for finishing the shoulder face and we should see that it is the surface is perpendicular to the spindle axis. When the shoulder face is not perpendicular to the spindle axis there is some inclination like this then when we this is the locating cylinder when we mount the chuck or face plate so there will be some inclination like this the chuck will be at some inclination with respect to the spindle axis because of this when we mount the workpiece in the three jaw chuck or face plate again the axis of the jaw will not coincide with the axis of spindle there will be some inclination because of this when we give the cuts so we get tapered surfaces. So to avoid this it is necessary that the shoulder face should be perpendicular with respect to spindle axis. Now the next test is true running of headstock center so this is the spindle inside there will be our tapered socket will be there and we mount the live center or headstock center in this tapered socket. Now the rotation of this live centered should be true there should not be any wobbling of the live center if it wobbles then the workpiece will also wobble along with the live center because of this the eccentricity will result on the workpieces. In order to test the true running dial gauge plunger should be placed on the tapered surface the plunger should be perpendicular to the tapered surface of the live center as shown here and the slowly the live center should be rotated and the dial gauge readings are taken the dial reading should not exceed 0.03 millimeter while conducting this experiment force F is applied on to the spindle or center in order to reduce the axial plane. Another very important test is parallelism of the main spindle to saddle movement in both the planes this test is conducted in horizontal plane as well as the vertical plane. You can see here we have the spindle and the mandrel with the tapered shank is mounted in the tapered socket of the spindle and the plunger of the dial indicator is pressed on the mandrel and the saddle is moved slowly and the dial indicator readings are recorded. If the spindle axis is not parallel to guideways then taper results on the workpiece. So when we move the dial indicator from one end to the other end in the vertical plane so the dial indicator will show whether the guideways are moving parallel with the spindle axis or not. Now the permissible error is 0.02 millimeter per 300 millimeter length of the movement in both the planes. So when we conduct this experiment the free end of the mandrel in the vertical plane should be rising. So in the vertical plane this free end should be upwards like this. If there is any error the free end should be upwards compared to this end in order to counteract the weight of mandrel or workpiece. So because the self at the workpiece it will tend to bend like this so that will nullify the effect of parallelism error if this end free end is upwards. Similarly in the case of horizontal plane the free end should be towards tool to oppose the tool. In the horizontal plane the free end should be towards the tool. So when the cutting action takes place because the cutting force tool pressure the workpiece will bend in the other direction against the. Now in the horizontal plane the free end should be towards tool to oppose the tool pressure. Now I can see the photographic views of the test. The mandrel taper shack mandrel is inserted into the spindle and the dial indicator flanger is in contact with the surface of the mandrel and it is mounted on the saddle. Now slowly at this place that is near the spindle nose so the reading is set to zero and slowly the saddle is moved in the longitudinal direction and what is the reading at the other end so that is recorded. So the difference will be what is the amount of error. So this experiment shows the parallelism test in the vertical plane. Now here we can observe the parallelism of the main spindle to the saddle movement in the horizontal plane. So the saddle flanger will be in contact with the mandrel like this in the horizontal plane then the saddle is slowly moved here the reading is set to zero and at the other end we have to slowly move the saddle at the other end what is the reading of the dial indicator we have to record the difference will give what is the amount of error parallelism error. Now another test that is normally conducted is true running of taper socket in the main spindle. So now we have the spindle nose the axis of the spindle and there is a tapered socket inside. Now whether the axis of this tapered socket is concentric with the main spindle axis so that we have to check sometimes this tapered tapered socket axis maybe at some angle like this so this is the main spindle axis that tapered socket axis maybe at some angle with respect to the main spindle axis or sometimes the tapered socket axis is parallel but there is some offset like this so now you can see this is the axis of tapered socket it is offset with the main spindle axis because of these errors eccentric and tapered jobs will be produced. Now we have to check whether the true running error is within the prescribed limits to conduct this test a mandrel is fitted into the tapered hole you can see here we have the mandrel with the tapered shank that is fitted into the tapered socket of the main spindle and then slowly the mandrel is rotated the spindle is rotated so that the mandrel is also rotated and dial gauge readings are taken at two extreme places that means initially we have to keep the dial and cater near the spindle and we have to slowly rotate the spindle and what is the amount of error that we have to note down and then we have to move the dial indicator to another place at a distance of 300 mm from the spindle and we have to see that plunger is in contact with the mandrel and again the mandrel is rotated and the reading is taken so in both the cases error should not exceed 0.02 mm at both the places. Now let us discuss about the parallelism of tie stock guideways with the carriage movement so in this picture we can observe that we have one set of guideways that is the inverted V guideway and one flat guideway for the movement of the tie stock and we have one flat guideway and one inverted guideway the second set of guideways for the movement of the carriage. Now these two sets of guideways should be parallel to each other if the guideways tie stock guideways are not parallel with the carriage movement that is if the tie stock guideways are not parallel with the guideways of saddle then there will be some offset of the tie stock center and this results in taper turning when the job is held between the two centers. In order to carry out this experiment we have to mount the dial indicator on the carriage and then the plunger should touch on the extended quill of the tie stock and then we have to clamp the tie stock as well as the tie stock sleeve and then we have to note down the reading and then we have to unclamp the tie stock we have to move the saddle and the tie stock together so that this distance is kept constant and then again at the second place on the bed again we have to clamp the tie stock and tie stock sleeve and then we have to take the like this at two three places along the length of the bed we have to take the reading and the maximum error should not exceed 0.04 millimeter so this experiment we have to conduct in both the planes and in both the planes vertical plane as well as horizontal plane error should not exceed 0.04 millimeter. Now let us discuss about moment of per slide parallel with the main spindle in vertical plane we can observe this photograph we have the guideways the guideways on the bed and then we have the saddle and then the cross slide cross slide and then above the cross slide we have another slide which is upper slide or two slide. Now the movement of the upper slide should be parallel to the spindle as otherwise tapered components will result so this test is conducted only in the vertical plane reasonings we can observe here there is a provision in the horizontal plane there is a provision for adjusting the swiveling in order to cut the taper the upper slide can be swiveled like this so the protractor we can see here we can swivel this upper slide to any angle required angle in order to get tapers so this test is conducted only in the vertical plane so we have to keep the stand magnetic stand on the upper slide and the dial indicator should touch the mandrel as shown here and then we have to take the reading we have to slowly move the upper slide and we have to note down the readings the difference in readings will keep the amount of error the permissible error is 0.04 millimeter per 300 millimeter and we should see whether the free end of the mandrel should be in the upward position to counteract the weight of the job now we can see how to conduct the tool slide movement parallelism with main spindle the mandrel is fitted into the spindle and the dial indicator plunger is in contact with the mandrel the magnetic stand is placed on the tool slide now slowly the tool slide is mowed and the dial indicator readings are taken the difference in readings give the error now we will discuss about another important test that is conducted the parallelism of tie stock sleeve to the saddle movement we can see here we have the body of tie stock inside we have the sleeve tie stock sleeve and it has a tapered socket inside in which the dead center can be inserted we can see the assembly drawing here the dead center and then we have the sleeve tie stock sleeve which can be mowed in and out using this wheel you can see the photographic view this is the tie stock sleeve and dead center for the jobs held between the two centers that is lie center and dead center the axis of dead center should be coaxial with the job axis in both planes that is horizontal plane as well as vertical plane now if this is not there then the tapered work pieces will result we do not get the cylindrical objects because of this shift now how do we test with this parallelism we have to extend the sleeve to the maximum extent and then we have to put the dial indicator stand or the saddle as shown here and the dial indicator plunger should touch the sleeve and then we have to lock the sleeve as well as the tie stock as normal working condition and slowly the saddle should be mowed and the readings are taken so the error parallelism error should not exceed 0.02 millimeter per 100 mm moment of saddle in both the planes now I can see the photographic views here so we have the tie stock body and the sleeve of tie stock it is fully extended and the dial indicator plunger is in contact with the external surface of the sleeve and the dial indicator stand is placed on the saddle and after locking the tie stock body and sleeve near the body we have to keep the dial indicator and we should adjust the reading to zero and then we have to slowly move the saddle so that the dial indicator moves to the other end of the sleeve and then the reading is noted so this reading should not exceed 0.02 per 100 mm moment of the saddle and the free end of the sleeve should be rising upwards in the vertical plane to counteract the weight of the work so when we load the workpiece between centers because the weight of the workpiece will be acting on this center and the sleeve tends to move down so initially the free end should be rising upwards before unloading the workpiece so similarly in the horizontal plane also this test is conducted we can see here the plunger is in contact with the sleeve in the horizontal plane and then slowly the saddle is moved and at the other end the reading is taken and this reading should not exceed 0.02 millimeter per 100 mm and the sleeve should be inclined towards the tool or the horizontal plane to oppose the tool pressure so the tool pressure will be acting like this so if there is any parallelism error this free end should be towards the tool now we will discuss about parallelism of tie stock sleeve taper bore to the saddle moment we can see here we have the tie stock and then we have the tie stock sleeve so the tie stock sleeve has a taper bore so this is the axis of sleeve and then we have the taper bore and we can fit the tapered dead centers the bore now it is necessary that the axis of taper bore should be parallel to the saddle moment otherwise tapered workpieces will result now in order to conduct this test mandrel is fixed to the tapered bore that we can observe here mandrel is fit into the taper bore of sleeve and the dial indicator is fixed to the tool post and the plunger dial plunger is pressed on the mandrel and then we have to lock the sleeve as well as tie stock as in normal working condition and then we have to slowly move the saddle and we have to note down the dial indicator readings the error should not exceed 0.03 mm per 300 movement of saddle and the free end of the mandrel should be towards frontwards in the horizontal plane to counteract the tool pressure and error should not exceed 0.04 mm per 300 mm the free end of the mandrel towards upwards in the vertical plane to counteract the weight of the workpiece I can see here the photographic views of the test the mandrel is fitted into the tapered bore of the sleeve the plunger is in contact with the outer surface of the mandrel and the dial indicator is fixed to the saddle so in this position the reading is adjusted to 0 and then slowly the saddle is moved after locking the tie stock and sleeve and then the dial indicator is moved to the other end of the mandrel and then again reading is taken now in the horizontal plane also the test is repeated you can see here the dial indicator is in contact with the plunger the reading is adjusted to 0 and then slowly the saddle is moved now the plunger dial plunger is in contact the mandrel at the end so again the reading is taken the difference gives the amount of error in the horizontal plane now let us discuss about alignment of both the centers in the vertical plane that is the headstock center height from the guideways and tie stock center height from the guideways should be seen if the heights are different then again the tapered components will result individually both the axis that is main spindle axis and tie stock axis may be parallel to the spindle axis but both the axis may be parallel to carriage movement but they may not be coinciding that means the heights may be different from the guideways so due to this when a job is fitted between the centers the axis of job will not be parallel to the carriage movement and tapered components will result now this test may not be conducted in the horizontal plane since tie stock can be adjusted in the horizontal plane so while conducting this experiment that is during taking the dial gauge readings tie stock and tie stock sleeve should be locked as in the normal working condition the magnetic stand of the dial indicator is placed on the tool post and the plunger of dial indicator should be made to touch the mandrel surface and then slowly the saddle is moved to the other end of the mandrel and then the reading is taken the difference in readings gives the alignment of centers in vertical plane I can see in this photograph the mandrel is placed between the live center and dead center the magnetic stand is placed on the tool post and the plunger is in contact with the surface of mandrel and then slowly the saddle is moved to the other end and then again the dial indicator reading is taken the difference gives the amount of error so this error should not exceed 0.06 millimeter per 300 millimeter saddle and if there is any difference in heights tie stock center should be higher than the head stock center the reason is with the continuous use of a tie stock the bottom surface of the tie stock will get overnought and the height of the tie stock center will reduce now if the error is more than 0.06 millimeter then the bottom surface of the tie stock is scraped and error is brought within the limits now we will discuss about the axial slip of the lead screw you can see the lead screw which is used during thread creating the thrust face and colors of the lead screw must be exactly square to the screw axis that means the thrust face should be perpendicular to the axis of the lead screw normal errors may be this face thrust face is not perpendicular to the axis that means there is some inclination like this or maybe some irregularities like this because of this a cyclic end wise movement is set up which is of the same nature as the axial slip of the main spindle because of this axial slip a periodic pitch error will be additional to any true periodic errors in the pitch of the screw so during screw cutting there will be error in the cut screws now in order to test this we have to put a steel ball as shown in this diagram and the plunger should touch the steel ball and the dial indicator will indicate we have to slowly rotate the screw and dial indicator will indicate if there is any error the axial slip should not exceed 0.03 millimeter now with this we will conclude module 11 lecture number one in this lecture one we discussed about the various aspects of machine tool metrology the need for machine tool metrology what are the various instruments used while conducting the machine tool metrology and what are the different types of tests alignment tests that is parallelism perpendicularity and then whether the movement of the various elements is parallel to the lathe axis such things we discussed and geometrical tests on the various tests conducted on that that also we discussed with this we will conclude lecture number one we will continue the discussion on the machine tool metrology in lecture number two thank you