Final answer:
A bonus tolerance in GD&T is an additional tolerance allowed under specific conditions indicated by the symbols in a feature control frame, usually involving the 'M' or 'L' modifier. The exact number of frames allowing for bonus tolerance depends on the part design. This concept facilitates manufacturing by increasing tolerances while ensuring quality.
Step-by-step explanation:
When we talk about feature control frames in the context of Geometric Dimensioning and Tolerancing (GD&T), a bonus tolerance is an additional tolerance for a geometric control that can be used under certain conditions. It comes into play when a feature control frame specifies a geometric tolerance that is related to the size feature of a part. For instance, if there is a positional tolerance on a hole that also has a size tolerance, when the actual hole size is larger than the minimum size but still within the specified size tolerance, a bonus tolerance is allowed.
By design, the number of feature control frames that specify a bonus tolerance will depend on the specific requirements of the part and its design. Any feature control frame that uses the “M” modifier (Maximum Material Condition) or “L” modifier (Least Material Condition) in the feature control frame may indicate the possibility of a bonus tolerance. It is important to read the feature control frame carefully and understand the symbology of GD&T to determine if a bonus tolerance applies.
The bonus tolerance is a key concept in GD&T because it allows for greater manufacturing tolerances while still ensuring that parts meet functional requirements. When the conditions are met, the bonus tolerance permits a larger tolerance zone, which can make it easier to manufacture parts without compromising on quality.