1. Lecture 2 – Clearance Fits
EML 2023 – Clearance Fits
Lecture 2 – Clearance Fits

2. Cylindrical Fits

3. Cylindrical Fits – English Units

4. Cylindrical Fits – English Units

5. Cylindrical Fits – English Units

6. Cylindrical Fits – English Units

7. Cylindrical Fits – English Units
tolerance - difference between the limits of size for a single feature ; shaft ; hole .0040
limits of tolerance – the max and min sizes of a single feature
allowance – the tightest fit between two mating parts ; .0050
nominal size – the general size of a shaft or hole ; 1.5
basic size – the size to which the plus-and minus is applied
actual size – the measured size of the finished part
fit - the degree of tightness or looseness between two assembled parts

8. Cylindrical Fits – English Units
clearance fit – gives a clearance between two assembled mated parts ;
min clearance .005 ;
max clearance .0115
transition fit
interference fit
line fit

9. Cylindrical Fits – English Units
clearance fit
interference fit – a binding fit that requires the parts to be forced together, much as if they were welded
transition fit – may range from a interference fit to a clearance fit between the mated parts
line fit – results in surface contact or clearance when limits are reached

10. Cylindrical Fits – English Units
The ANSI B4.1 standard defines a series of fits between cylindrical features in inches for the basic hole system.
The types of fits covered in the standard are:
RC: running or sliding clearance fits
LC: clearance locational fits
LT: transition locational fits
LN: interference locational fits
FN: force and shrink fits

11. Cylindrical Fits – English Units
RC: running or sliding clearance fits
RC1 to RC9
LC: clearance locational fits
LC1 to LC11
LT: transition locational fits
LT1 to LT6
LN: interference locational fits
LN1 to LN3
FN: force and shrink fits
FN1 to FN5

12. Example – RC9 Fit hole and shaft have a basic diameter of 2.5”
From Tables in Appendix 29
thousands of an inch

13. Example – LT3 Fit hole and shaft have a basic diameter of 2.5”
From Tables in Appendix 31
2.5012
2.5000
2.5008
2.5001
thousands of an inch

14. Example – LN2 Fit hole and shaft have a basic diameter of 2.5”
From Tables in Appendix 32
2.5012
2.5000
2.5021
2.5014
thousands of an inch

15. Example Problem

16. Cylindrical Fits – Metric Units
ANSI B4.2 standard
basic size – the diameter from which limits are calculated
upper and lower deviation – the difference between the hole or shaft size and the basic size
tolerance - the difference between the maximum and minimum sizes

17. Cylindrical Fits – Metric Units

18. Cylindrical Fits – Metric Units
fundamental deviation – a letter grade that describes the deviation closest to the basic size
International Tolerance (IT) grade – a series of tolerances that vary with the basic size to provide a uniform level of accuracy within a given grade
there are 18 IT grades: IT01, IT0, IT1, …, IT16

19. Cylindrical Fits – Metric Units
Hole basis
a system of fits based on the minimum hole size as the basic diameter
the fundamental deviation for a hole-basis system is “H”
Appendices 35 and 36 give hole-basis data for tolerances
Shaft basis
a system of fits based on the maximum shaft size as the basic diameter
the fundamental deviation for a hole-basis system is “h”
Appendices 37 and 38 give shaft-basis data for tolerances

21. Cylindrical Fits – Metric Units

22. Cylindrical Fits – Metric Units

23. Example 1 determine the shaft and hole limits for: hole-basis system
a close running fit
a basic diameter of 49 mm
use a preferred size

25. Example 1
use a preferred basic diameter of 50 mm
use a fit of H8/f7

26. Example 2 determine the shaft and hole limits for: hole-basis system
a location transition fit
a basic diameter of 57 mm
use a preferred size

28. Example 2
use a preferred basic diameter of 60 mm
use a fit of H7/k6

29. Example 3 determine the shaft and hole limits for: hole-basis system
a medium drive fit
a basic diameter of 96 mm
use a preferred size

31. Example 3
use a preferred basic diameter of 100 mm
use a fit of H7/s6

32. Nonstandard Fits, Nonpreferred Sizes
determine the shaft and hole limits for:
hole-basis system
a close running fit
a basic diameter of 45 mm (do not change to a preferred size)

34. Nonstandard Fits, Nonpreferred Sizes
use a fit of H8/f7