DIMENSIONAL TOLERANCES AND METHODS OF FITS

1
Lesson 10

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• DIMENSIONAL TOLERANCES AND METHODS OF FITS

• Importance of dimensional tolerances
• Definitions
• Tolerancing method
• Type of fits
• Methods of fits
• Fits and deviations

2
IMPORTANCE OF DIMENSIONAL TOLERANCES

• The workman cannot be expected to produce the
  exact size of part as indicated by the dimensions
  on a drawing.
• a certain amount of variation on each
  dimension must be tolerated.
• Especially, the problem of
  interchangeable manufacture developed from the
  making of parts to a supposedly exact size to the
  holding of part sizes between two limits lying so
  closely together that any intermediate size would
  be acceptable.

3
DEFINITIONS

• Basic size (?? ??) reference size
• Limit of size
• The maximum and minimum sizes permitted for a
  specific dimension.
• Maximum limit of size (?? ?? ?? ??)
• Minimum limit of size (?? ?? ?? ??)

4
DEFINITIONS

• ?? ?? ?? A 50.025 mm, a 49.975 mm
• ?? ?? ?? B 50.000 mm, b 49.950 mm

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DEFINITIONS

• Deviation (?? ??? ?? ???) limit of size - basic
  size  
• Upper deviation
• maximum limit of size - basic size
• Lower deviation
• minimum limit of size - basic size

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DEFINITIONS

• Zero line (???)
• ?? ?? 50.000 mm

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DEFINITIONS

• Tolerances Total permissible variation in its
  size
• maximum limit of size - minimum limit of size
• Upper deviation - Lower deviation
• Allowance The intentional difference in
  correlated dimensions of mating parts

8
TOLERANCING METHODS (?? ?? ??)

• Limit dimensioning Only the maximum minimum
  dimensions are specified

9
TOLERANCING METHODS

• Plus and minus tolerancing The dimension of the
  specified size is given first, followed by
  expression of tolerance.

10
TOLERANCING METHODS (?? ?? ??)
11
TOLERANCING METHODS (?? ?? ??)
12
TOLERANCING METHODS (?? ?? ??)
13
TOLERANCING METHODS (?? ?? ??)
14
TYPE OF FITS (?? ??? ??)

• Clearance (??) Interference (??)
• Clearance bore diameter gt shaft diameter
• Interference bore diameter lt shaft diameter
• Clearance fit (??? ?? ??)
• Transition fit (?? ?? ??)
• Interference fit (?? ?? ??)

15
TYPE OF FITS (?? ??? ??)

• p. 280 ? 13-6

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TYPE OF FITS (?? ??? ??)
17
TYPE OF FITS (?? ??? ??)
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METHODS OF FITS (?? ?? ??)

• Basic bore system (???? ?? ??)
• Basic size use a minimum limit of size of the
  bore
• H5 - H10

19
METHODS OF FITS (?? ?? ??)

• ???? ?? ?? ??

20
METHODS OF FITS (?? ?? ??)

• ???? ?? ?? ??

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METHODS OF FITS (?? ?? ??)

• Basic shaft system (? ?? ?? ??)
• Basic size use a maximum limit of size of the
  shaft
• h4 - h9

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METHODS OF FITS (?? ?? ??)

• ???? ? ?? ??

23
METHODS OF FITS (?? ?? ??)

• ???? ? ?? ??

24
ISO TOLERANCE (IT ?? ??)

• 0 mm - 3150 mm ? ?? ??? ??
• 21???? ??? ??

25
ISO TOLERANCE (IT ?? ??)
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ISO TOLERANCE (IT ?? ??)

• IT ?? ?? ??? ?
• 6? ?????
• ?? Ø 35 Ø45 ?? 0.016 3050? ??
• ?? Ø 200     ?? 0.029 180250? ??
• ?? 6? ?? ????? ???? ??? ??.
• ??? ???? ??

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FIT AND DEVIATION

• ??? ?? ?? ? ??

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FIT AND DEVIATION

• ???
• ??  Ø (??) (???? ??) (??)
• ? Ø12H7 ? ? ?? ??? 0.018, ???? ??? 0
• ?  Ø (??) (???? ??) (??)
• ? Ø100H7 ? ? ?? ??? 0, ???? ??? - 0.035
• ?? ?? ??
• ? H8/g7

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FIT AND DEVIATION

• ?? Ø30f8 ? ?? ? ?? ??? ? ???? ???? ????.
• f? ? ?? ???? ??? ?? ?? ???
•  ? 10-5 ? ? ?? ??? -20
•  ? 10-3 ? IT ???? 33
• ? ?? ??? - ???? ??? IT ????
• (-20) - (???? ???) 33
• ? ???? ??? -53
• ?

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FIT AND DEVIATION
31
FIT AND DEVIATION

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32
FIT AND DEVIATION

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