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Geometric positional tolerance is given of.1 mm with modifier M. The modifier has specific meaning, It add a bonus tolerance. When shaft is at MMC there will b . GD&T bonus tolerance is an important concept for design engineer. This article will explain the Geometric Dimensioning and Tolerancing concept with an. When geometric tolerance is applied to a feature of size and it contain a MMC modifier in the tolerance portion of the feature control frame.

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With an LMC specification, when the tooling core pin is largest, it needs to bobus located more precisely to ensure machining stock is available. But how is this possible with LMC of a hole See the attached excerpt?

bobus When that envelope departs from the LMC size, you have more material to work with and therefore can physically and by design permit more tolerance. The axis of the hole must lie entirely within the tolerance zone for your part to be accepted by inspection. How much bonus you will get?

There are a few formulas associated but the main one is to calculate your virtual condition. Bonus tolerances can reduce manufacturing costs significantly.

This ensures a bigger hole “stays” in place while smaller hole can “move around” like a planetary gear. This does not work well when you are considering a pattern of holes that function together such as a bolt hole pattern.

What size is the one use to calculate bonus at LMC?


It’s easy to join and it’s free. There is no difference in what’s happening. Tolwrance do plan on circling back and adding valuable content to the website in tolsrance future though. Figure shows how bonus tolerance is calculated in a straightness application. When the MMC modifier is used, it means that the geometric characteristic can be verified with a fixed gage.

The statement is true only if location of the hole is controlled by position tolerance defined at MMC basis. This could appear after the tolerance or after the datum as applicable. Here are some handy rules of thumb as to when to use which material condition MMC — Assembly, locations of non-critical fitments as you state LMC — Minimum g&t thickness or minimum distance between featuers, alignment RFS — Control of symmetrical relationships, centering and alignment.

If location of the hole is controlled by position tolerance defined at LMC basis, you get addtional bonus tolerance when the hole starts to get smaller, that is, it starts to move from its LMC towards MMC.

My original question If we have specified originally pos.

Result the mating part with pin will be off position more That’s my question in first palce. Here you would use the larger tolerance zone to locate your hole and your perpendicularity call-out to restrict the tilt of the whole to a tighter degree. The Eng-Tips staff will check this out and take appropriate action. I hope this helps. So the increasing hole’s center can “fool around” by this additional amount of bonus tolerance, still fitting with the pin.


It all really depends on application. The goal here is functional assembly of your parts. At MMC the maximum available tolerance will be equal to. What do you mean when you give zero tolerance at mmc? Sure, stir the pot, and make the quick exit. Another example for a useage that benefits with the application of LMC is a precast hole intended for subsequent machining.

Bonus Tolerance Calculation – GD&T

If the locating is not important, and the hole and shaft merely need to fit together, I would go for mmc on hole.

But how gdnt ensures they fit together is over my head. Here’s what you need to understand: Alex Kurlikovski Fundamentals book should be your best friend for the weekend. Bonus tolerance in LMC “the tolerance should get stricter”?? Have a nice weekend everybody!! When the MMC modifier is used in the tolerance portion of the feature control frame, it means that the stated tolerance applies when the feature of size is at its maximum material condition.

Bonus Tolerance

We can explain it to you, but we cannot understand it for you! Out of which specified positional tolerance is 0. I don’t get annoyed when I am corrected. Td&t internal feature hole is MMC at 9. Figure 2 Figure 2 shows how to determine the amount of bonus tolerance permissible in an application.