 Hello everyone, this is Shila Ratnabanswade from Walchand Institute of Technology, Solapur. Today we are going to see the topic transition fit, learning outcomes. At the end of this session, students will be able to describe transition fit. Now moving further, look at the images on the screen, the first, second and the third. At this moment, I suggest you to pause the video and see the relation between the hole and the shaft for all the three images. Now coming back, in the first image, the hole and the shaft have a gap or a considerable gap in between them. In the second image, the gap between the hole and the shaft is bit reduced. And in the third gap, in the third case, the gap between the hole and the shaft is zero. The size of the hole and the size of the shaft are nearly equal. So these are the various types of conditions which defines fits. Here the gap is more, here the gap is reduced and here there is no gap at all. So moving further, fits can be defined as the relation between two mating paths. As said earlier in this image, the relation between the hole and the shaft. In the first case, the second case and the third case, here it is loosely fitted, here a bit loose and here it is exactly equal to the size. Moving further, the degree of tightness or looseness as shown in the previous figures, fits can be defined as the degree of tightness or looseness. Fits are classified on the basis of the actual limit of the hole or shaft. The actual limit here represents or mentions the actual sizes of the hole or the shaft. Depending upon the actual size of the hole or shaft, we can have clearance fit, the first image, interference fit, the second and third and transition fit, the first and the second. Moving further, let us have a look on transition fit. Transition fit may result into either a clearance or interference fit. It comprises, it is a compromise between clearance and interference fit. Depending upon the dimension of the hole and the shaft, we get either a clearance or an interference fit in the case of transition fit. It is used when accurate location is important between the shaft and the hole. So transition fit may either result into a clearance fit or interference fit depending upon the sizes of the hole and the shaft that is including the tolerance level. Now let us see the transition fit on hole base system and shaft base system. First on the left hand side of the screen you can see the hole base system and on the right hand side you can see the shaft base system. As far as hole base system is concerned, this is the zero line or the base line and the yellow color box shows the tolerance zone of the hole. So minimum of the hole coincides with the zero line. Thus the size of the hole is fixed whereas the small red color boxes on the screen represents the tolerance zone of the shaft. So as you can see the tolerance zone of the shaft over here, over here and over here. This position gives you the clearance fit and this gives you the interference fit. So you can see the sizes of the shaft are changing whereas the size of the hole is fixed. Thus this system is known as hole base system. Now coming to shaft base system, again we have the zero line or the zero line or the base line. Now the red color box towards the right hand side shows the tolerance zone of the shaft. So here the upper limit of the shaft coincides with the zero line. Thus the size of the shaft is fixed or the tolerance zone of the shaft is already fixed. Now the small yellow color boxes represents or shows the tolerance zone of the hole. So here you can see this is one size, this is another size and this is the third size. So dimension of the shaft and dimensions of the hole. So clearance fit, two interference fit, we have these represented on a shaft base system. So here you can see the difference between the hole base system and the shaft base system for the case of transition fit, moving on further. Now look at this diagram, this is the hole and this is the shaft. The sizes of the hole are maximum size is 30.05 and minimum size is 29.95 whereas the maximum size and the minimum size for the shaft is maximum is 30 and minimum is 29.05. Now in this case we may have either a clearance fit or an interference fit depending upon the sizes of the hole and the sizes of the shaft. For example if we consider the size of the hole as 30.05 and the size of the shaft as 29.95, we will get a clearance fit as maximum size of the hole is used with the minimum size of the shaft. So maximum of hole and minimum of shaft will give you clearance fit. Apart from this if we consider the hole size as 29.95 and the shaft size as 30, in this case we get the interference fit. So maximum of shaft and minimum of hole will give you interference fit. So this is an example of transition fit. So here you can see how the tolerance or the sizes of the shaft and the hole decides whether the resulting fit will be a clearance fit or a interference fit. Now transition fit where we have these types of fits or the types of transition fits. First the push fit it refers to zero allowance and a light pressure. The moving parts show least vibration with this type of fit. It is also known as snug fit. In this case the shaft easily gets inserted into the hole without much effort and the moving parts if available will give least vibrations. So moving further we have force fit or shrink fit. The force fit is used when the two mating parts are to be rigidly fixed so that one cannot move without the other. So if you want to have zero relative motion between the two mating parts we go for this type of fit that is force fit or shrink fit. It either requires high pressure to force the shaft into the hole or the hole to be expanded by heating. So in this case either we use high pressure to force the shaft into the hole or we heat the hole so that it gets expanded and the shaft can be accommodated in it easily. It is used in railway wheels and etc. The heating hole example can be of PVC pipes where we heat one side of the pipe and we insert the other side of the pipe or the other pipe into it or we can simply say that PVC fittings. Moving further the wringing fit a slight negative allowance exists between the two mating parts in wringing fit. It requires pressure to force the shaft into the hole and gives a light assembly. As compared to force fit the wringing fit requires a bit low pressure to insert the shaft and the two holes and the shaft do not get in contact with each other rigidly as the case is in force fit or shrink fit. It is used in fixing keys, pins etc. Thus the clearance or the gap between the hole and the shaft in case of wringing fit is bit considerable as compared to the same in the force fit. So here the shaft can be easily removed from the hole or by using a light pressure but the case in the case of force fit or shrink fit you require pressure to insert the shaft into the hole and the same to remove the shaft from the hole. So we have seen force fit or shrink fit and wringing fit. These are the references thank you.