 Hello, students. This is Mr. Nagesh R. Tambake, Assistant Professor, Department of Mechanical Engineering, Valkchon Institute of Technology, Sholapur. Today, we are going to discuss the topic that is Mechanisms of Lake Machine. Learning outcome. At the end of this session, students will be able to explain mechanisms of lake machine. In this particular session, we are going to discuss introduction, center lathe, speed cone pulley drive, back gear mechanism, tumbler reversing mechanism, geared headstock, apron mechanism. Now, first of all, we will think on this particular question that is, what is lake machine? A lake machine is a machine tool which is used to remove metals from a workpiece to give a desired shape and size. In other words, it is a machine that is used to hold the workpiece to perform various metal removing operations, such as turning, grooving, chamfering, knurling, facing, forming, etc. with the help of tools. Lakes are widely used machine tools in the mechanical industries, factories, warehouses, and manufacturing units. Now, this is the center lathe in which the entire setup is fixed on a rigid legs. On the legs, the rigid bed is present, that is made up of a cast iron. And on the lathe bed, we are having the headstock and tailstock. On the headstock, we are fitting a chuck inside that the job is going to hold. And to the chuck, the motion is given by the speed cone pulleys. And that is also called as live center. And at the opposite end, there is a tailstock. Between these two, the job is going to hold and the operations are performed. And to cut the metal, we require a tool and that tool is going to fit on the tool post and which is fitted on the swirling compound rest. And that swirl compound rest is fitted on the carriage. And carriage is covered by the apron and inside which whatever the mechanism is placed, that is called as apron mechanism. And now we will see the mechanisms of lathe machine one by one. This is the speed cone pulleys drive. Now, in this particular schematic sketch, you can see two cone pulleys are having four steps and are placed parallel to the spindle cone pulleys. Both the cone pulleys are connected by a flat or V-belt. The belt can be arranged between the steps A and H, B and G, C and F, and D and E. The cone pulleys at the bottom is connected to the electric motor by a V-belt. So the cone pulleys at the bottom rotates at a particular speed. Now in a schematic sketch, if you see, the spindle speed will be maximum when the belt is arranged between A and H. And the spindle speed will be minimum when the belt is arranged between the D and E. As we know simply, when an input shaft is having low diameter and the output shaft is having more diameter, in that case we will get more torque and less speed. And in the reverse case, vice versa, means we are getting a maximum speed but less torque. Back gear mechanism from the previous whatever the speed cone pulleys that we have discussed, from that we are getting four speeds that are the forward speeds. And that are the maximum speed where the material is very soft. For that purpose, we are using a more speed. Now with this back gear mechanism, we are getting four lower speeds. With this back gear, what will happen? The torque is going to increase. Suppose the material is, if it is very hard, then definitely we are going to use this back gear mechanism to remove the material from the job. Now how it is operating? In this type, power is transmitted to the spindle via two step cone pulleys and requires the use of belt drive to connect them. A pinion gear is mounted with small end of cone pulleys. In this type, a bull gear is also used which can be locked or in unlocked position through lock pin and is keyed through that particular a bull gear. So here whenever we apply the key that time what will happen? So whatever the bigger gear, bigger gear of back gear is there that is connected to the smaller gear of the speed cone pulleys and likewise the torque is going to increase and we are getting less speeds to the spindle so that we can remove the material of the harder offset. Next one, tumbler reversing mechanism. Whenever we require a job to be removed, a bore material, that time initially we need to take a forward, forward speed. In that case we are removing the material and whenever we apply the tumbler reversing mechanism that time carriage is going to run in a reverse way so that the tool is going to place again in the original starting position so that continuously the metal is going to remove. So in this how the mechanism is going to operate? Reversing mechanism is used to change the direction of carriage either from headstock to steel stock or vice versa. Change gear quadrant with quick change gearbox is used to provide us different feed rates to lead screw and feed rod. The sole purpose to use tumbler gear mechanism is to reverse the direction of lead screw and the feed rod automatically. Gear headstock. This particular gear headstock we are using instead of the speed cone pulleys. Here you can see at the left hand side the fast and loose pulleys is present. Whenever a belt is connected between the fast pulley of the gear headstock and the motor that time the motion is transmitted to the gear headstock from the motor and whenever the belt is going to shift towards the loose pulley then loose pulley is continuously rotating but in from the gear headstock no gear is going to rotate. So in this particular figure how it is operating that we will see in this type the constant motor speed is provided to the gear arrangement but depending upon the requirement of speed it changes using gear arrangement which is controlled by levers. These levers change their position to generate different combinations to acquire different speed. For example if now in this case in this particular figure now g2 gear is measured with g5 and g5 gear is measured with g8. Now what is happening the belt is connected between the fast pulley of the gear headstock and the motor and that particular motion is transmitted to the g2 gear and g2 to g5 and g5 to g8 and that particular speed is going to apply to the life center so that with that speed the workpiece is going to rotate. Likewise different nine combinations that we are getting from this particular headstock and different nine speed that we can obtain from this gear headstock. Apprent mechanism this mechanism is situated inside the carriage and that whatever that housing of that particular mechanism is there that is called as apprent and inside which what the mechanism is located that is called as apprent mechanism. Apprent is attached to the carriage and hangs over the front side of the lathe bed. It is useful in providing power and hand feed to both carriage and cross slide. It is also used to provide power feed to the carriage during thread cutting through two half nuts. Now here in this particular schematic case you can see whatever the g6 gear is there that is connected to the lathe screw that is placed transversely to the lathe bed and which will give the transverse motion to the carriage of the lathe machine and whatever the g3 gear is there that will give the longitudinal field to the carriage of the lathe machine and here at the right hand side you can see the half nut that is connected to the lathe screw and that particular half nut mechanism we are using whenever we need to cut a threads on the chop. This is half nut mechanism in the detail. Half nut mechanism is used to move carriage on the lathe screw and also for automatic thread cutting. In this case you can see whenever we apply the lever that time what will happen two half nuts are coming closer to each other and it is going to hold the lathe screw and that time what will happen a half nut is going to engage with the lathe screw and that time the carriage is moving with the lathe screw and initially whatever the tumbler mechanism is there that is connected that is connected to the lathe screw and due to that automatically the lathe screw is rotating with the help of that lathe screw the lathe screw is connected to the half nut and whenever half nut is having some threads due to that the carriage is moving over the lathe bed for cutting the screws cutting the threads on the work piece. These are the references Bloom's Taxonomy and Hazra Choudhary elements of workshop technology volume two media promoters and P N Rao that is a book which is of that is published by P N Rao manufacturing technology metal cutting and machine tools Tata McGrawill publications New Delhi and also you can refer a Raghu Moshi book that is manufacturing technology again. So in this particular session we were discussed different mechanisms of the lathe machines from which we are going to we will get how the mechanism is going to work inside the lathe bed and how that are operating and one will know how to operate the machine with the help of this knowledge.