 Hello students. This is Mr. Nagesh Arthambake, Assistant Professor, Department of Mechanical Engineering, Valtran Institute of Technology, Sholapur. Today, we will discuss on problems on spindle speed and thread cutting on lathe machine. Learning outcome. At the end of this session, students will be able to solve the problems on spindle speed and thread cutting operation on lathe machine. In this particular session, we are going to discuss calculation of spindle speed by different combination of the cone pulleys and bag gears. Next one, that is, what is thread cutting operation on lathe machine? Setup of lathe for thread cutting. Calculation of chain gears for thread cutting. Now first of all, we will solve one problem regarding the spindle speed, that is, calculation of spindle speed by different combinations of cone pulleys and bag gears. In this particular figure, the two spindle pulleys are shown and that are connected to the motor and motor is driving those pulleys. Now the problem I will read first, that is, a lathe having cone pulleys drive carries a four-stepped cone pulleys. The diameters of the four steps are 100 mm, 140 mm, 180 mm, 220 mm. The pinions on the spindle and bag gear shaft each carry 20 teeth while the machine gears carry 60 teeth each. If the machine motor drives the counter shaft at a speed of 300 rpm, calculate the different speeds which can be obtained for the lathe spindle. Here we can see, for one-speed cone pulleys there are four steps. Therefore, at only different combination of cone pulleys, we will get four different speeds. And by connecting the bag gears, engaged to the spindle speed cone pulleys, we are getting another four speeds. Therefore, in total we are getting eight speeds over here. Now, we will calculate the spindle speed by different combinations of the cone pulleys. Here in this particular figure, the belt is connected to A and H position of the pulley. Now, first of all, we will calculate the speed at position. Now, here in the given data, whatever the smaller diameter of pulley is there, that is 100 mm, then 140 mm, then 180 mm, then 220 mm, these are the diameters of speed cone pulleys. And also, the speed of the spindle that is given, that is 300 rpm. Now, first of all, we will calculate spindle speed at belt in position D, that is the first position in which the input diameter is 100 mm and the output diameter is 220 mm. And we know the spindle is rotating with the speed of 300 rpm. Whatever the input of the input gear that is rotating with 300 rpm. Therefore, here 300 into 100 upon 220, if we calculate, then we are getting 136.4 rpm. That speed we are getting for the spindle. Now, next one is second speed, spindle speed at belt in position Cf. Therefore, input diameter over here, that is 140 and output diameter over here, that is 180. Therefore, the input speed, the motor drives, that is 300 rpm into 140 upon 180, that will give us 233.3 rpm. This is the second speed. Now, third speed at third position of the belt, that is BG position, where the input diameter is 180 and output diameter is 140. Therefore, 300 into 180 upon 140, that will give us 385.7 rpm. This is the third speed that we are getting. And now, fourth speed is spindle speed at belt in position H, that is input diameter of the pulley is nothing but 220 mm and output diameter is nothing but 100 mm. Therefore, 300 into 220 upon 100, we are getting 660 rpm. These are the four speeds that we are getting by different combinations of cone pulleys. Now, next one, spindle speeds by bag gears. We know over here, the pinion is having 20 teeth and the bull gear is having 60 teeth each. Therefore, now, this particular bag gear is connected to, now that is for the spindle cone pulleys. Therefore, here, whatever the key over here it is there, that is we are unlocking. Therefore, whatever the speed is coming towards this speed cone pulleys, that is transferred to this pinion and pinion to that of bull gear and with the same speed, this pinion is again rotating and with this pinion, this bull gear is having the speed. Therefore, 20 upon 60 and 20 upon 60, this multiple factor, if we multiply with the spindle speed, then definitely we are getting the again four different spindle speeds. Therefore, at different speed cone pulleys in position, we will get different four speeds. Now, here you can see spindle speed at building position D. The first speed in the position D that we got, that is 136.4. Therefore, multiple factor of number of teeth, if we multiply over here, that is 20 by 60, 20 by 60, that is driving upon driven, driving upon driven, then this is the reduction factor. Therefore, we are getting, that is minimum speed, 15.2 rpm. And this particular 15.2 rpm is the minimum speed of the lathe machine and that which we are using for the hard, for the removal of harder material. Next one, spindle speed at building position Cf. Here, the second speed that we got in a normal position, that is 233.3 into 20 upon 60 into 20 upon 60, that we are getting 25.9 rpm. Likewise, if we calculate spindle speed at building position Bg by back gear, then we got the third speed, that is 385.7 into 20 upon 60 into 20 upon 60, if we multiply this factor, then we are getting 42.9 rpm, that is the seventh speed. And eighth speed is spindle speed at building position A h by back gear, is 660, that last speed that we got, that is fourth speed, into 20 upon 60 into 20 upon 60, we will get 73.3 rpm. This is the highest speed of the spindle when the back gear is attached. Likewise, eighth speeds we can calculate for the spindles and that we can arrange for the spindle and according to the requirement, we can get different speeds for the spindle. Now, next one is, I will ask one question to you, what is thread cutting operation on lathe machine? Please think on it and try to get the answer. Now, thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading tool bit, the same shape as the thread form required. Thread of any pitch, shape and size can be cut on the lathe using single point cutting tool. Thread cutting is operation of producing a helical groove on spindle shape, such as V square or power threads on a cylindrical surface. This is a setup of lathe for thread cutting. The job is held in between the centers or in a check and the cutting tool is held on the tool post. The cutting tool must travel a distance equal to the pitch in mm, in inch, in diametrical and in module as the workpiece completes a revolution. The definite relative rotary and linear motion between job and cutting tool is achieved by locking or engaging a carriage motion with lead screw and nut mechanism and fixing a gear ratio between headstock spindle and lead screw. To make or cut thread, the cutting tool is brought to the start of job and a small depth of cut is given to cutting tool using cross slide. Now we will take one example. Calculate the change gears for cutting 1 mm pitch on lathe having lead screw, lead screw of 4 TPI. P is required pitch on workpiece in mm and is pitch of lead screw in TPI. Therefore the formula that we are having is driver's gears upon gear teeth upon driven gear teeth is equal to 5 pn upon 127 into ratio factor. Here 5 pn upon 127, the ratio factor is 27 upon 36. Therefore 5 is the required pitch on the workpiece and 1 is the pitch on the lead screw that is in TPI, 1 TPI and 4 that we have added, 5 is the 4 that is the required pitch on the workpiece. And likewise we are getting 5 into 10 upon 187 into 3 into 10 upon 100. Here the multiple factor is 25 upon 25. Therefore we will get the gear ratio 30 upon 127 into 50 upon 100 and a gear that we are putting it as 30, b is 127 and c is 50 and b is 100. Therefore this is the spindle gear, this is the intermediate gear and this is the lead screw gear. Therefore a is 30, b is 127, c is 50 and d is 100. If you put these gears then definitely we will get the 1 mm pitch across the, across the job. So these are the references. Thank you, thank you.