302 GD&T: Application and Interpretation Copyright Goodheart-Willcox Co., Inc. Regardless of Feature Size No material condition modifi er is used to spec- ify regardless of feature size (RFS) because RFS is implied. See Figure 8-10. The assumed RFS condition indicates that the specifi ed tolerance value remains constant, regardless of the produced size of the toler- anced part feature. A hole specifi cation and position tolerance are shown in the given fi gure. Limits of size for the hole are .500″ and .510″ diameter. The position tolerance is specifi ed as .025″ diameter RFS. Any hole produced within the limits of size is permitted a position tolerance of .025″ diameter. The size of the hole has no effect on the allowable posi- tion tolerance because the tolerance is applicable RFS. Two examples of produced holes are shown. One hole is produced at .500″ diameter, the maxi- mum material condition for the hole. The position tolerance for this hole is .025″ diameter. The other hole is produced at .510″ diameter, the least material condition for the hole. The position tolerance for this hole is also .025″ diameter. RFS is typically used for applications where holes have zero clearance or press fi ts. The allow- able diameter variation on a press fi t hole does not provide any additional position tolerance. Therefore, RFS is required. RFS may also be used for clearance holes that locate other parts. Two boundaries are created by a position toler- ance that is applicable RFS on a hole. There is an inner boundary that is equal to the MMC hole size minus the position tolerance. An outer boundary is created by the LMC hole size plus the position tolerance. For the inner boundary, the given fi gure shows four circles at the MMC size and at four different loca- tions at the allowable limits of the position tolerance relative to the same true position. An inscribing circle is drawn representing the inner boundary. Any hole produced within the size and position tolerance will not violate this boundary. For the outer boundary, the given fi gure shows four circles at the LMC size and at four different loca- tions at the allowable limits of the position tolerance relative to the true position. A circumscribing circle is drawn representing the outer boundary. Any hole produced within the size and position tolerance will not violate this boundary. The inner and outer boundaries are not size lim- its for the hole. They are not the minimum size or maximum size used for calculating the fi t of a mating part and they are not acceptance boundaries that can be used to check the hole location. They are simply worst case boundaries that the surface of the hole is not to cross. The boundaries are important for design considerations where edge distances, potential effect on assembly variation, or other variation effects need to be analyzed. Maximum Material Condition The maximum material condition (MMC) modi- fi er is a letter “M” inside a circle and is shown follow- ing the tolerance value. See Figure 8-11. The shown specifi cation is for a hole. The MMC modifi er indicates that the specifi ed tolerance value applies only when the hole is actually produced at MMC. If the hole is produced at any allowable size other than MMC, the position tolerance value increases an amount equal to the size departure from MMC. When using the axis method of verifi cation, the allowable increase in positional tolerance is based on the size of the unrelated actual mating envelope of the hole instead of the size of the hole. Because the following examples have no form variation, the size of the hole and the size of the unrelated actual mating Produced hole sizes and allowable position tolerances Inner and outer boundaries Hole specification and position tolerance Ø.500 Hole produced at MMC size at LMC size Ø.510 Hole produced RFS assumed Ø.025 Allowable Ø.510 LMC size position tolerance Ø.500 MMC size Ø.475 Inner boundary Ø.025 Allowable position tolerance Ø.025 Allowable position tolerance Ø.025 Allowable position tolerance Ø.535 Outer boundary Goodheart-Willcox Publisher Figure 8-10. The position tolerance zone is not affected by the produced feature size when RFS is applicable to the tolerance value.