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).
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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