What is Regardless of feature size (RFS) in GD&T?

In Design of any machine elements, it is necessary to follow the Geometric dimensioning and tolerancing for the Holes or shafts. The Regardless of feature size(RFS) is the feature of the size where it can be called out for a hole or a shaft when there is no need of MMC or LMC.

Regardless of feature size

This means that it does not matter whether the size is at it’s low or high limit of its noted tolerance and that the GD&T limit does not change.

Example for Regardless of feature size

If the hole on a given part was made to its smallest size (2.74 mm).

The pin on a given mating part was made to its largest size (2.46 mm).

the worst case allowable variation that could be allowed for the position would each be 0.14 mm

Total variation allowed between the two parts= 2.74 mm – 2.46 mm = 0.28 mm

It clearly shows that this condition to reflect the worst case line-to-line fit.

If, however, the size of the hole on a given part was made to its largest size (2.86 mm).

The pin on a given mating part was made to its smallest size (2.34 mm).

It would make sense that the worst case allowable positional variation could be larger than 0.14.

Evaluating this further as was done above to determine a line-to-line fit would be as follows:

The total variation allowed between the two parts= 2.86 mm – 2.34 mm = 0.52 mm

It would seem natural, due to the combined efforts of size and positional tolerance being used to determine the worst-case virtual condition boundary, that there should be some means of taking advantage of the two conditions.

The Feature of Size Callouts in GD&Ts

• Maximum Material Condition

• Least Material Condition

• Regardless of Feature of size