 Welcome back MechanicalEI. Did you know that limits, fits and tolerances highly influence both minor and major decisions, ranging from material selection to the entire cost of the manufacturer product? This makes us wonder, what are limits, fits and tolerances? Before we jump in, check out the previous part of this series to learn about what thread designation is. First, let's clear out some terminology. The term shaft refers not only to the diameter of a circular shaft, but to any external dimension on a component. And the term hole refers not only to the diameter of a circular hole, but to any internal dimension of a component. Now, the term limits, or limits of size, refer to the two extreme permissible sizes for a dimension of a part, between which the actual size should lie. The largest permissible size for a dimension is called its upper limit, whereas the smallest size is called lower limiting. Fit refers to the degree of tightness or looseness between two mating parts. Depending upon the actual limits of the hole and shaft, they may be classified into the following three types. In clearance fit, which is the first type, the minimum size of the hole is either greater than or equal to the maximum size of the shaft, so that the shaft can rotate or slide as per the purpose of the assembled members. A fit that everywhere provides interference between the hole and the shaft when assembled is known as an interference fit. This is the second type of fit. In interference fit, the maximum size of the hole is either small or equal to the minimum size of the shaft. Finally, a fit which may provide either a clearance or an interference fit between the shaft and hole when assembled, depending on the actual size of the manufactured shaft and hole is known as transition fit. The term tolerance refers to the difference between the upper limit and the lower limit of a dimension. In other words, tolerance is the maximum possible variation in a dimension. The tolerance may be of two types, that is unilateral or bilateral. When the tolerance is allowed on one side of the nominal size, then it is said to be unilateral system of tolerance. When the tolerance is allowed on both side of the nominal size, then it is said to be bilateral system of tolerance. Hence, we first saw what limits and fits are and then went on to see what tolerances are. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also, thanks a lot for those constructive comments. You helped the channel grow. So, here are the top mechanical EIs of our last videos. In the next episode of Mechanical EI, find out what assembly drawing is.