Tolerance

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# Tolerance - PowerPoint PPT Presentation

Geometric Tolerances and Dimensioning. Tolerance. Why Geometric Tolerancing and Dimensioning. To ensure interchangeability of mating parts during assembly To eliminate controversy and guesswork when drawing is interpreted

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## PowerPoint Slideshow about 'Tolerance' - jesse-levine

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Presentation Transcript

Geometric Tolerances and Dimensioning

### Tolerance

Why Geometric Tolerancing and Dimensioning
• To ensure interchangeability of mating parts during assembly
• To eliminate controversy and guesswork when drawing is interpreted
• To ensure the drawing reflects the form and function requirements of the manufactured parts
Tolerances are used to control the variation that exist on all manufactured parts.
• Tolerance dimensions control the amount of variation on each part of an assembly.
• The more accuracy needed in the machined part, the higher the manufacturing cost
Limit Dimensions
• Limits:

The lower and upper allowable sizes are

referred to as the limit dimensions

• Tolerance is :

a. Upper limits: Larger value

b. Lower limits: Smallest value

Tolerance Representation:

Tolerance can be expressed in several ways:

1. A general tolerance note in the title block

FIT TYPE
• If one part is to be inserted into or mated with another part, The type of fit can be determined by the following:
• The loosest fit is the difference

between the smallest feature A

and the largest feature B.

• The tightest fit is the difference between the largest feature A and the smallest feature B
Mating Parts
• Mating parts are parts that fit together with a reasonably high degree of accuracy.
Terminology of Tolerancing
• When the shaft and hole are assembled ,the extreme conditions are the tightest and the loosest fit
Methods of noting tolerance
• TOLERANCE, UNILATERAL - A tolerance in which variation is permitted in one direction from the specified dimension.
TOLERANCE, BILA TERAL - A tolerance in which variation is permitted in both directions from the specified dimension
Fit types

A.Allowance.

• Clearance fit
• Interference fit
• Transition fit

E. Line fit

Clearance fit: Is the fit that gives clearance between

two assembled mating parts.

Allowance fit: The allowance is the tightest fit between

two mating part.

.

Interference fit: Is the fit that leads to interference between two assembled parts.

Chain Dimensions
• Parts are dimensioned to locate surfaces or geometric features by chain of dimensions
Datum Plane The accumulation of tolerances can be reduced by measuring from a single plane called datum plan