![]() ![]() Bonus Tolerance = Pin diameter at MMC – Pin diameter at LMC = 25 – 15 = 10.In this first video, the center axis of the cylinder representing the pin at MMC displaces around the position tolerance zone, which is defined as a cylinder with a diameter of 5mm.Įxample 2: Pin diameter at Least Material Condition The concept of MMC and bonus tolerance becomes much clearer if visualized in 3D. In our example (Figure 3):Įxample 1: Pin diameter at Maximum Material Condition ![]() If the pin is finished at less than its MMC and closer to its LMC limits, the clearance gained can be used as a bonus tolerance for form or position. In this case, Bonus Tolerance = MMC-LMC=25-15=10.Ĭlearance for assembly increases if the actual sizes of the mating features are less than their MMC. Bonus tolerance equals the difference between the actual feature size and the MMC of the feature. Bonus tolerance explained: As the size of the pin departs from MMC toward LMC, a bonus tolerance is added equal to the amount of that departure. Thus, MMC is widely used in cases where clearance fits are common.įigure 3. When a hole is at its smallest (MMC) and a pin is at its largest condition (also MMC), we can be sure that we will still be able to assemble that part. MMC defines the worst case condition of a part that will still guarantee, because it is still within the prescribed tolerances, the assembly between pin(s) and hole(s). In our example in the animated Figure 2, we can observe that the MMC of the pin is 25 mm, while the LMC is 15 mm. LMC is the condition in which there is the least amount of material, the largest hole or smallest pin, within the stated limits of size. ![]() ![]() MMC is the condition of a feature which contains the maximum amount of material, that is, the smallest hole or largest pin, within the stated limits of size. Maximum Material Condition (MMC) and Least Material Condition (LMC): Simple Definitions Our example replicates the case in the Figure 2.15 in the ASME Y14.5-2009 standard (page 33) in a 3D context with much larger tolerances (and errors) to better visualize the concepts. The goal of this blog post is to analyze the effect of the MMC (Maximum Material Condition) concept on a pin (shaft) in a 3D context with a simple example (Figure 1). One of the reasons for this difficulty is the visualization problem of 3D concepts in 2D documentation. Geometric Dimensioning and Tolerancing concepts are often difficult to grasp at first beginners can have quite a difficult time understanding the basic principles. Geometric Dimensioning and Tolerancing: 2D versus 3D. ![]()
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