Think Boundary, not Bonus - 1994, 2009, 2018 (#22)
(In accordance with the ASME Y14.5-2018 standard)
(In accordance with the ASME Y14.5-2009 standard)
(In accordance with Y14.5M-1994 standard)
The typical approach to inspecting a feature such as the Ø1.000 mm hole is to measure the mating size, calculate a bonus tolerance, and determine if the axis of the hole is within the total allowable position tolerance. Another approach is to measure the surface of the hole, to see if it violates the virtual condition. If a hard gage were produced to inspect the position of this hole, it would have a pin with Ø.970 mm (+gage tolerance and wear allowance), which is the virtual condition diameter, located at the hole’s true position from the datum reference frame as defined by basic dimensions.
This hard gage may be simulated using a height gage in an open setup or a CMM with a touch probe. By adding or subtracting half the virtual condition from the basic dimensions, the radial distance from the true position that may not be violated by any point on the surface may be calculated. These distances may be easily inspected.
This tip is in accordance with ASME Y14.5M-1994, ASME Y14.5-2009 and ASME Y14.5-2018.
This tip was originally released in March 1999 and updated May 2026.
