ABSTRACT
With the advent of the least material condition (LMC) concept, the circled L (©) was allowed to be included in the feature controls. This happened in the ANSI Y14.5 Standard in the 1982 revision. This LMC concept was most often used for the preservation of material for wall thicknesses. For example, if someone was creating a casting drawing and was concerned that the casting have enough material to be cleaned up during a machining operation to be conducted according to requirements called out on a subsequent drawing (used by the machine shop), the LMC symbol was often utilized. It had the advantage over the MMC symbol of stating that the more material a feature was produced with the
more imperfect it could be, for example, in its location or orientation. The use of this LMC symbol created a whole new functionality. The most important boundary under those circumstances was material preservation, as might be the case with a hole in a drinking straw-the smaller the hole in the straw, the more it may move out of perfect coaxiality with the outside diameter without endangering the minimum wall thickness required for part integrity.
