Virtual Condition
For a shaft that fits into a hole, the shaft virtual condition must be smaller than the hole virtual condition.
For an external feature of size such as a shaft, the virtual condition is equal to the size at MMC plus the size of the position tolerance zone.
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| Shaft with MMC applied |
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| Shaft Virtual Condition |
For an internal feature of size such as a hole, the virtual condition is equal to the size at MMC minus the size of the position tolerance zone.
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| Hole with MMC applied |
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| Hole Virtual Condition |
Since the shaft virtual condition is smaller than the hole virtual condition, the two parts will always mate.
Virtual condition is extremely useful in design of functional gauges. A functional gauge made to virtual condition will ensure that a part will always mate with its counterpart.
In summary, the way to calculate virtual condition (VC) for a shaft and hole is:
SHAFT VC = MMC Diameter + Position Tolerance Zone Diameter
HOLE VC = MMC Diameter - Position Tolerance Zone Diameter
Resultant Condition
For a internal feature of size, the resultant condition is the variable value and outermost boundary.
For a external feature of size, the resultant condition is the variable value and innermost boundary.
The way to calculate resultant condition (RC) for a shaft and hole is:
SHAFT RC = AME - Total Tolerance
HOLE RC = AME + Total Tolerance
HOLE RC = AME + Total Tolerance
Whereas AME is Actual Mating Envelope &
Total Tolerance = Bonus Tolerance + Geometric Tolerance
Lets us consider a case study for Virtual & Resultant condition.
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| Internal feature of size |
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| Calculation Table Internal feature of size |
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| External feature of size |
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| Calculation Table External feature of size |
Summary
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| Comparison Table for Internal Feature of size |
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| Comparison Table for External Feature of size |
Note : virtual condition and resultant condition are applicable only for specification with material condition. Therefore in Regardless of feature size ( RFS ), the similar substitute are inner and outer boundary.
