![]() Two boundaries are created by a position toler- ance that is applicable at LMC on a hole. Another example is a hole in a casting where the position of the hole must be adequately controlled to ensure subsequent machining operations will have material for removal. Examples are a clearance hole centered in a boss or a structural hole near the edge of a plate. The LMC modifi er is typically used for applica- tions where edge distance or remaining material is of concern. ![]() The position tolerance for this hole is increased to. 500″ diameter, the maximum material condition for the hole. ![]() The position toler- ance for this hole is. 510″ diameter, the least material condition for the hole. Two examples of produced holes are shown. 001″ increase in the diameter of the position tolerance zone. 001″ diameter decrease in hole size, there is an allowable. Any hole produced at a smaller diam- eter is permitted a larger amount of position toler- ance. 510″ diameter is permitted a position tolerance of. Any hole produced at the exact LMC size of. A hole specifi cation and position tolerance are shown in the given fi gure. Because the form of each hole shown in the following examples has no variation, the size of the hole and the size of the actual mini- mum material envelope are the same. For a hole, the unrelated actual minimum material envelope is the smallest circumscribing cylinder that is inside the material. When using the axis method of verifi cation, the allowable increase in positional tolerance is based on the size of the unrelated actual minimum material envelope of the hole instead of the size of the hole. This is similar to the MMC concept, except it uses the LMC size as the size to which the original tolerance value is applied. If the controlled feature is produced at any allowable size other than LMC, the position tolerance value increases an amount equal to the size departure from LMC. The LMC modifi er indi- cates that the specifi ed tolerance value applies only when the controlled feature is actually produced at the LMC size. Least Material Condition The least material condition (LMC) modifi er is a letter “L” inside a circle. ![]() ![]() The boundaries are important for design considerations where edge distances, potential effect on assembly variation, or other variation effects need to be analyzed. condition is not an acceptance boundary that can be used to check for hole position. 304 GD&T: Application and Interpretation Copyright Goodheart-Willcox Co., Inc. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |