Limit fit & Tolerance

Limit fit & Tolerance :

Unilateral tolerance :variation is only one direction

Bilateral tolerance : variation on both side

Fundamental deviation: basic size

Tolerance = upper limit - lower limit :Permissible limit of variation for manufacturing is assigned to parts for manufacturing purpose as boundary of acceptable build.

Basic size: Nominal diameter of shaft or hole it is same for both

Fit: it is clearance between two mating parts, it can be determined by whether the parts move, temporary joint ,permanent joint.

Clearance fit: Hole is larger than shaft.

Transition fit: Hole is fractionally smaller than shaft.

Interference fit: Hole is smaller than shaft.

Functional dimension : have to be machined and fit with other mating parts.

Drilling : unilateral Dimension

BIS (Bureau of International Standard)

Grade of Tolerance :18

Fundamental tolerance : 25

BSI (British standard System)

Grade of Tolerance :16

Fundamental tolerance : 21

IS (International Organisation System)

Grade of Tolerance :18

Fundamental tolerance : 28

ES= Upper limit

EI = lower limit

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