 Hello friends, myself, N. S. Katikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Today we are going to see the presentation on various types of FIT. Learning outcome for my presentation. At the end of this session, student will be able to understand the need and importance of FITs. Student will be able to identify and apply the type of FITs in real time. Contained for my presentation, introduction, need of FIT, type of FIT, whole basis system, shaft basis system, and some of the examples. In the introduction, let us see there is an importance of limit, tolerances and FIT in the machine drawing. As we are aware, the output of machine drawing, rather the machine drawing contains the various type of drawings like production drawing, assembly drawing and other drawing applications, where the mechanical elements are required to be shown with their specific dimensions along with the tolerances. As far as in the case of assembly, there will be the need to show the various kind of FIT. That is, the relation between two distinct dimensions of two distinct or respective elements. Thus, the various limit sizes are also required to be shown in the production drawing, with which the respective manufacturing or production method can be controlled. Let us see the need of FIT. The FIT as we have seen just now, it is the relation between the various dimensions of particular elements which are mating each other. The various conditions like inaccuracies present in the machines and the tools, inaccuracies in the setting the work of the tool, then the particular error in the measurement of various specifications, as well as the human interference error are the some of the reasons because of which there will be the need to provide the FIT for various kind of mating elements. At this stage of session, are you able to recall, share some of the application of FIT anywhere you had seen or used earlier in the drawing or the sketches. That means, because of the FIT, the assembly is going to be in a real fruitful sense as far as its delivery point of view. The working of the assembly is going to deliver successfully the satisfaction of that particular assembly from the user point of view that is because of the various type of FIT. Try to imagine such assemblies rather the parts and enlist. Now, let us go technically with the various type of FIT. First one is the clearance FIT. This is the FIT with these two diagrams we will try to able to understood. This is the conceptual figure clearance FIT where the sharp dimension is always less than the whole dimension. As we aware, as you know at the time of particularly terminologies of various limit fits and tolerances, we learn that in the universe whatsoever the two mating parts are there are categorized into two major element. One is whole element that is which carries the internal geometries and other is sharp which carries the outer peripheral geometries. Now, from that particular point of view let us describe the clearance FIT is nothing but the sharp dimension. This is the lower limit size. This is the upper limit size. These two dimensions limit sizes are always less than the basic size of whole rather the any limit sizes of the whole. Now, that is the way vary the particular clearance may be minimum clearance. This is the minimum clearance and this is the maximum clearance. So, minimum clearance to maximum clearance the particularly there will be always a positive gap. So, this is the one of the example where you can see that positive gap is present between the sharp and the whole. The second type of fit interference fit now where again with this particular conceptual figure will try to understood what exactly the interference fit means. The sharp element is always a little bit bigger size than that of the whole element where you could found over here that lower and upper limit of sharp this is a lower and this is the upper limit of sharp. These two limit sizes are always greater than any of the particular whole sizes rather the upper limit size of the whole. So, lower limit and upper limit of sharp always greater than upper limit of whole. That means we can say there is a negative clearance between the two mating parts. There is a negative dimensional gap between the two mating parts. Like this particular example we can see that the minimum interference to the maximum interference. So, in any particular condition the sharp is greater than whatever the minimum or maximum value of the whole. So, the sharp is of bigger size always in the case of interference fit. The clearance fit and interference fit in other words we can say that opposite to each other. The third type of fit now in this third type of fit where the transition fit includes sharp and whole in a three distinct cases. And ultimately we can say that transition fit includes clearance fit as well as transition fit. With the actual size combinations of whole and sharp the particular incidental case may vary from clearance to interference. In this particular diagram conceptual figure we can see that how the lower and upper limit sizes of the sharp may positioned with respect to the lower and upper limit sizes of whole. For example, this is the first case where partially the tolerance zone of sharp is overlapping with the whole tolerance zone whereas in second case this is the second case where the tolerance zone of sharp is within the tolerance zone of whole. In the third case the tolerance zone of sharp is little bit overlapping and over and above the tolerance zone of whole. Now as I said with the actual dimensions or sizes of the whole and sharp element the particular type of fit will in existence. For example in this first figure if at all the lower limit size of sharp is the actual size and upper limit size of the whole is the actual size then there this is result as a clearance fit vice versa when the limit size of sharp that is upper one matches with the actual size of sharp and lower limit of whole is the actual size of whole then there will be the negative clearance that is interference fit. So in real time it will run accordingly with this example we can see that the how transition fit will in existence. Now let us proceed with the particularly system with which the dimensions or fit can be referred. Now basically there are two distinct basis system one is whole basis system another is sharp basis system. Now let us discuss about the whole basis system and its relevance with the particular type of fit. Here you can see that this diagonal hatching pattern is representing the whole rather the whole tolerance and this one indicates the sharp tolerance zone. Now here you can see that stage wise the sharp tolerance is moving from bottom to the right top. The type of fit will also change in this first situation it is clearance in the last situation it is interference and this one indicates the transition fit. Now the design size of the sharp can be calculated by deducting the allowance from the basic size of the whole accordingly the respective dimensions can be calculated. The whole basis system is used because the whole can be very well adjusted or drilled with the means of drilling, reaming and so on. Whereas in sharp basis system the sharp and whole here tolerance zones are shown and obviously the particular first case is clearance, last case is interference and intermediate particularly stages explains or represent the transition fit. Now particularly sharp basis system is going to be shown over here the particularly whole basic dimensions are considered for the calculations of sharp tolerance. In sharp basis system you can see over here the sharp upper limit is nothing but matching with the basic size that is deviation is 0 it is indicated by small h whereas whole basis system the lower limit size of whole is matching with the zero line that is datum line that is the basic size deviation is 0. So it is going to be considered by capital H so some of the particular examples of clearance transition and interference are as follows. Some of the examples realistic examples of fit varies from interference transition to the clearance are as follows. The particular various type of fit and their examples with the class of fit references are as follows. Thank you.