Example of Bonus Tolerance
Say, you have a drawing of a block with a hole like below:
Observe the GD&T control frame. The meaning of the GD&T symbol is: “a positional tolerance of 0.2 is applicable to the hole when it is at the maximum material condition (MMC)".
You already know that MMC for the hole will have the diameter of 10.2 and at this condition there should have a positional tolerance of 0.2 means for inspecting the hole you should use a gauge of diameter 10. All the holes that allow the 10 diameter gauge to enter should pass the quality checks.
At MMC the maximum clearance available between the gauge and the hole is 0.2, so available tolerance at MMC is 0.2.
Now as per the given dimension the hole diameter can vary from 10.2 to 10.5, and as the hole size increase the tolerance available between the gauge and the hole also increases. At MMC the maximum available tolerance will be equal to
10.5 – gauge diameter = 10.5 – 10 = 0.5. Out of which specified positional tolerance is 0.2 so the bonus tolerance will be (0.5 – 0.2) = 0.3.