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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 61Lecture #6 EGR 110 – Engineering GraphicsReading Assignment: Ch. L in Engineering Graphics Workbook, Series 1.2 or Series 2Sketching Assignment: Sketching Assignment #5Dimensioning Example - Work problem DIM-6 in class (Engineering Graphics Workbook, Series 1.2, by Craig & Craig). Grids are 0.25”.2Lecture #6 EGR 110 – Engineering GraphicsToleranceTolerance - the total amount of variation permitted for a specific dimension- the difference between the maximum and minimum limitsLimit Dimensions - the minimum and maximum dimensionsExample: If a dimension is 0.875  0.003, determine the:•Maximum dimension•Minimum dimension•Limit dimensions•Tolerance3Lecture #6 EGR 110 – Engineering GraphicsWhy is tolerance important?The use of interchangeable parts would be limited unless the accuracy of each part was controlled.No parts can be made to exact size. Even finely machined parts will vary by some small amount (for example: one thousandth of an inch). Keep in mind that increased accuracy (smaller tolerance) results in increased costs. An engineer must carefully weigh the cost of each tolerance that he specifies.CostTolerance0.10.010.0010.00014Lecture #6 EGR 110 – Engineering GraphicsTolerance examplesTolerance can be expressed in various ways. Some examples are shown below.SymmetricaltoleranceNon-symmetricaltolerance(deviation)Limit DimensionsTolerance is often expressed using notes as shown below (add hole dimension).GEN. TOL. ±0.02 UON3.507.002.755.505Lecture #6 EGR 110 – Engineering GraphicsMating Shafts and CylindersTolerance is particularly important in mating parts, such as a shaft and a cylinder. In some cases the shaft may fit loosely into a cylinder (clearance fit) or in other cases it may fit very tightly (interference fit). With a clearance fit, the shaft is slightly small than the cylinder and with an interference fit, the shaft is slightly larger than the cylinder.A couple of terms are important with mating shafts and cylinders:Maximum clearance = Maximum cylinder dimension - Minimum shaft dimensionAllowance (= minimum clearance) = Minimum cylinder dimension - Maximum shaft dimensionNote that allowance will be negative for an interference fit.ShaftCylinder6Lecture #6 EGR 110 – Engineering GraphicsExample: For the mating shaft and cylinder below, determine:•Shaft tolerance•Cylinder tolerance•Maximum clearance•Allowance•Is it a clearance fit or an interference


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TCC EGR 110 - EGR 110 LECTURE NOTES

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