1. Tolerance Dimensioning
Interchangeable Manufacturing
Tolerancing
Nominal Size
Basic Size Actual Size
Allowance
By B. Cowan &
R. Cash

2. Mass Production Interchangeable manufacturing allows parts made
in widely separated localities to be brought together
for assembly. That the parts all fit together properly is
an essential element of mass production. Without
interchangeable manufacturing, modern industry could not exist, and without effective size control by the engineer, interchangeable manufacturing could not be achieved. Dimensions should be given to as large a
tolerance as possible without interfering with the function of the part to reduce production cost. Manufacturing to close tolerance is expensive.

3. Basic Dimension
Toleranced Dimension

4. Unilateral Tolerance Bilateral Tolerance Unilateral Tolerance allows
variation in only one direction.
From basic size.
Bilateral Tolerance
Bilateral Tolerance allow variation
in either direction from basic size.

5. Other Methods Of
Positioning and
Indicating Tolerances
Bilateral and
Unilateral

6. Specify Tolerance By Note
NOTE: All dimensions Plus or Minus 1/16 Inch

7. Tolerance

8. Tolerance

9. Glossary Of Terms
Mating Parts are parts that fit together within a degree
of Accuracy.
Tolerance is the difference between the limits
prescribed for a single part.
Allowance is the tightest fit between two mating parts.
Nominal Size is an approximate size that is usually
expressed with common fractions.
Basic Size is the exact theoretical size from which
limits are derived. The basic size expressed as a
decimal

10. Shaft Hole Tolerance is the difference between
the limits prescribed for a single part.
The Tolerance for the Shaft is .002
Hole

11. Allowance is the tightest fit between
two mating parts. The smallest hole
and the largest shaft. The Allowance
for the Shaft and Hole is .003

12. 2 1/2 Inch Shaft
Nominal Size
Basic Size

13. Type of fits between mating parts when assembled.
Clearance Fit is a fit that gives a clearance between two assembled
mating parts.
Interference Fit is a fit that results in an interference between the two
assembled parts. The Shaft is larger than the hole.
Transition Fit can result in either an interference fit or a clearance fit.
The shaft can be either larger or smaller than the hole.
Line Fit can result in a contact of surfaces or a clearance fit between
shaft and hole.
Page 389

14. American National Standard of Limits and Fits
RC Running or Sliding Clearance Fits - Intended to provide a
similar running performance with suitable lubrication allowance.
Piston in a car.
LC Locational Clearance Fits - Intended to determine only the
location of the mating parts.
FN Force Fits or shrink fits constitute a special type of
interference fit, normally characterized by maintenance of
constant bore pressure throughout the range of sizes.
Page 393

15. Example: Specify a RC3
Fit for the 1 1/4 Inch Shaft
and Hole
See Page a25 in the Appendix

16. Nominal Size Range Hole Shaft
Basic Size
Nominal Size Range Hole Shaft

17. Nominal Size Range Hole Shaft
Multiply by .001
Nominal Size Range Hole Shaft

18. Nominal Size Range Hole Shaft
Add or Subtract From Basic Size
To Calculate Tolerance.

19. Nominal Size Range Hole Shaft
Hole = =
Shaft = =

20. Hole = =
Shaft = =