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.





Shaft with MMC applied

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.





Hole with MMC applied

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

Whereas AME is Actual Mating Envelope &



Total Tolerance = Bonus Tolerance + Geometric Tolerance



Lets us consider a case study for Virtual & Resultant condition.





Internal feature of size

Calculation Table Internal feature of size

External feature of size

Calculation Table Ex ternal feature of size

Summary



Comparison Table for Internal Feature of size

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.







