 Good morning all. This is Shila Ratna Bansode from Walchand Institute of Technology, SolarPort. As a part of machine learning curriculum, we are going to deal with the topic, free hand sketches and in that we will be dealing with types of threads. Let's move further, learning outcomes. In this session or at the end of this session, students will be able to draw different types of threads and will also come to know how or what kind of nomenclatures are related to threads. Moving further, now threads form a part of fasteners. Fasteners are machine elements that are used for joining or holding two or more machine parts or structure and the process of joining the parts is called as fastening and the component or the machine element used for this process is called as fasteners. Now depending upon the type, we have two types that is permanent and removable fasteners. Now permanent fasteners, once you apply these fasteners or once when you join the two parts with the help of these fasteners, you cannot remove it. Without any destruction, you cannot remove these kind of fasteners. If you want to disassemble the two parts, if you want to separate the two parts, you have to break the fastening agent that you have used and on the other hand, you have removable fasteners. In removable fasteners, the two parts can be disassembled or made separately by removing the fastener easily. There is a provision in removable fasteners where you can remove the fasteners. You can dismantle the fasteners from the two parts being joined. Now as a part of permanent fasteners, riveting and welding are permanent fasteners. You all know riveting. Riveting is used for joining especially sheet metals in burst bodies, pressure vessels and etcetera and welding is quite familiar. Any type of welding is a permanent joint or gives you permanent joint, rivets also gives you permanent joint. If you want to remove or separate two parts that are being riveted, you need to break the rivet. Similar is the weld joint. If you want to disassemble or separate two parts that are being welded, you need to break the welded joint. You need to cut the welded joint. On the other hand, we have screwed fasteners. Remove fasteners, the combination of nut and bolt, set screws or other type of joining materials or machine components. These can be removed as and when required. If you consider a nut and bolt arrangement or two parts being joined by nut and bolt arrangement, merely by turning the nut or bolt, we can disassemble the two parts. Removing the nut and bolt arrangement, we can disassemble the two parts. This was with fasteners, where we have seen permanent and removable fasteners. Permanent fasteners, riveting and welding, whereas removable fasteners, screwed fasteners. Removal fasteners are also used where frequent assembly and disassembly is required. Frequent joining and removal of the two parts or separation of the two parts is required. Moving further, now coming to screwed fasteners. Screwed fasteners are frequently used as I mentioned, where you have frequent assembly or disassembly of the two parts being joined. Wherever you want to remove or you want to have a temporary joint for time being or for specific period of time, you want to join the two parts. There, you can go for screwed fasteners. If you want to modify such kind of parts, you can merely remove the fasteners and the modification can be done in the parts. Screwed fasteners occupy the most prominent place among the removable fasteners. So screw fasteners are very much preferred. They are used to hold parts together. They are also used to adjust the reference of one part with another. They are also used to transfer power. So adjustment specifically are used, as I mentioned, adjustment of the parts specifically used for set screws. The screw or the small handle that you have in a wristwatch is also a screw. It's a set screw. Another example where you set a reference for is your carburetor, where you arrange the set screw to have the proper flow of charge. Now as far as screw fasteners are concerned, bolts, studs, nuts in combination and machine screws or set screws. These are the popularly used screwed fasteners in any engineering or non-engineering applications. Nut and bolt arrangement is the most common that you will be able to see in most of the components. Highly visible or highly popular is nut and bolt arrangement. Then the screws. Studs are similar to bolts, but they don't have a head. On both the sides they have threadings, whereas bolt you have threading on one side and a head, a shape, hexagonal or round or dome shape or square shape on one side. So this was with screwed fasteners. Let's move further. Now as we are going to see about threads, now as I said thread is a part of screwed fasteners. So what are the nomenclatures that we have as far as threads are concerned? Here you can see a major diameter and a minor diameter here. Now major diameter is the diameter of the rod before forming the threads on it. So this area, this area, this area is your major diameter before forming the thread. This diameter is called as major diameter. Then the minor diameter. Once you form the threads on the shaft, this lower end, this lower end, this lower end forms the minor diameter, forms the minor diameter. Then we have pitch diameter. We have pitch diameter. Pitch diameter is an imaginary, is a diameter of an imaginary circle. Pitch diameter is the diameter of an imaginary circle or a cylinder that passes through the points or passes through the same point on each thread where the distance between two points is constant, where the distance between two points is constant. It passes through such points. This is an imaginary circle and hence it is the diameter of an imaginary circle, pitch diameter. Then we have crest. Now in this threads, the topmost point, the topmost point, the topmost point, the topmost point, these all topmost points are called as crest. This upper part is called as crest. This is called as crest. The circle passing through crest is called as major diameter. The cylinder passing through crest is called as major diameter. bottom part the bottom part the bottom part is called as root the bottom part is called as root. The minor diameter touches these bottom parts now these faces that touch the root and crest that touches crest and root this side and this side is called as flank everywhere it is called as flank the angle between these two lines crest and root crest and root this V angle is called as angle of thread it is called as angle of thread. Then here you can see the indication of P indication of P is the same is the distance between two same adjacent points or two points adjacent two points on the same position. If you consider a point on this side the similar point on this side left hand side is the distance that is called as pitch this is called as pitch. Now here you can see external threads here you can see external threads here is an example of internal threads here is an example of internal threads. So with respect to external threads and internal threads we have the definitions at crest root flank major diameter minor diameter pitch diameter pitch and angle of thread. So this is the screw thread nomenclature that we have moving further. Now these are some of the forms of threads that you can see that are mostly available in any applications. The first one that you see is sharp V thread you can see on the screen the shape is pointed here it is pointed the included angle is 60 degrees for sharp V thread and this is the pitch distance between two same adjacent points. Then we have with word thread bit rounder form of V thread then we have buttress thread combination of square and V thread. Then we have square thread highly load carrying capacity of square thread is high. So used in screw jacks V thread is used in set screws then we have acme threads a bit root area is more as compared to square threads then we have worm thread moving further thread designation thread is designation in ISO form as with a letter m then a nominal diameter and then the pitch they are separated by an x here we you can see an example m 10 into 1.25 m is the metric designation 10 is the nominal diameter and 1.25 is the pitch then we have single start and multi start threads single start thread consists of only single helical group whereas multi start threads have depending upon double start or triple start two or three helical group starting at an specified angle. When you turn a single start thread it moves only by one pitch that is lead is equal to pitch lead is the horizontal distance that the thread travels whereas in multi start threads if you consider double start thread when you turn the nut or screw by one rotation it moves two times the pitch so lead is equal to pitch similar in triple start thread lead is equal to three times of P. So this was with single start and multi start thread then we have right hand and left hand thread right hand thread is one which advances when you turn it in right hand direction left hand thread is the one which advances when you turn it in left hand direction. So this is left hand thread and light and tightening and loosening directions are specified by left hand and right hand thread. These are the references. Thank you.