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Chapter 12 Tolerancing Tolerancing: Basic Shaft System The basic shaft system of calculating tolerances is based on using standard shafting. Holes are then machined to any size desired. The minimum shaft size is taken as the basic size and tolerances are applied to both the shaft and hole. Given the following specifications find the limit dimension for both the shaft and the hole using the Basic Shaft System” Nominal size Fit 2.0000 RC8 Using the American National Standard Running and Sliding Fits table cross reference the nominal hole size (2.00) with the Standard Limits values Hole +4.5 -0 Shaft -6.0 -9.0 Convert the numbers to thousands by moving the decimal point 3 places to the left or dividing the numbers 1000. Hole +0.0045 -0.0000 Shaft -0.0060 -0.0090 Reverse the values and the signs of the hole and shaft. Hole +0.0060 +0.0090 Shaft -0.0045 +0.0000 Add or subtract the values to the nominal size to find the upper and lower limits dimensions of the hole and shaft Hole 2.0000 +0.0060 2.0060 2.0000 +0.0090 2.0090 Shaft 2.0000 -0.0045 1.9955 2.0000 +0.0000 2.0000 The limits dimension for the hole diameter is (2.0060-2.0090) and the limits dimension for the shaft is (1.9955-2.0000). 1 Chapter 12 Tolerancing The minimum allowance is the difference between the smallest hole and the largest shaft. Minimum Allowance 2.0060 Smallest Hole -2.0000 Largest Shaft 0.0060 Minimum Allowance The maximum allowance is the difference between the largest hole and the smallest shaft. Maximum Allowance 2.0090 Largest Hole -1.9955 Smallest Shaft 0.0135 Maximum Allowance 2