Slide 1
A tolerance defines acceptable variation
A machining tolerance states how far a dimension or geometry may vary while the part remains acceptable. No real process produces perfect mathematical forms.
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The required range should follow function. A decorative surface and a bearing seat can need very different precision, even when both appear on the same component.
Slide 2
Shaft and hole tolerances combine at the fit
A shaft and hole must fit together across their possible sizes. Their separate tolerances combine to determine clearance or interference.
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For guaranteed assembly, designers consider the limiting combinations rather than comparing only nominal sizes. Two parts each close to nominal can still create an unsuitable fit if the allowances were chosen poorly.
Slide 3
Datums provide references for measurement
Datums provide reference features for locating and orienting measurements. They connect inspection with the way the part functions or is assembled.
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A hole’s diameter can be correct while its position is wrong. Geometric control therefore goes beyond adding more decimal places to a size dimension.
Slide 4
Wear, heat, vibration and clamping change the result
Tool wear, temperature, vibration and clamping can alter the produced geometry. A stable machine still needs a controlled process.
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A thin part may spring back after clamps are released. Measuring only while it is heavily restrained can hide the final shape that matters in assembly or service.
Slide 5
Measurement uncertainty matters near a limit
Inspection uncertainty must be considered relative to the tolerance. An ambiguous measurement near a limit needs an appropriate decision rule.
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Tightening every tolerance raises manufacturing and inspection demands. Good design assigns precision where it changes function, preserving wider allowances where they do not compromise the product.