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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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Thank you for helping keep Eng-Tips Forums free from inappropriate posts. There is no difference in what’s happening. Download Now White Paper: In revisions to the standard earlier thanthe symbol to indicate that the tolerance was to be taken at RFS was an S enclosed in a circle. Although a straightness control is used for the example in Figure 1, the bonus tolerance concept applies to any geometric control that uses the MMC or LMC modifier in the tolerance portion of the feature control frame.

The result is an LMC hole most precisely held locationally. At MMC the maximum available tolerance will be equal to. Let’s assume, you have a positional callout for the hole with MMC. I think they were occidentally swapped. Have a nice weekend everybody!!

Bonus Tolerance Calculation – GD&T

Like a -ve Bonus tolerance. Sure, stir the pot, and make the quick exit. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

The internal feature hole is MMC at 9. So if you get some “bonus” from your employer that means you salary will be smaller stricter right? If locating is important for a hole and golerance shaft, then the “play” between them can be arrested by an Lmc modifier. Any help would be appreciated. Another example for a useage that benefits with the application of LMC is a precast hole intended for subsequent machining. Result the mating part with pin will be off position more I still don’t get the concept of bonus tolerance in the snip I attached earlier.


Close this window and log in. A functional gage does not provide a dimensional measurement; it only indicates if the tolefance is or is not to the print specification. The problem for mmc is incorrect. This section is an introduction to the bonus tolerance concept.

When the actual mating size of the feature of size departs from MMC towards LMCan increase in the stated tolerance— equal to the amount of the departure — is permitted. What do you mean when you give zero tolerance at mmc? But how gdnt ensures they fit together is over my head.

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GD&T Symbols

A functional gage is a gage that is built to a fixed dimension the virtual condition of a part feature; a part must fit into or onto the gage. That’s my question in first palce.

The bonus tolerance reduces the number of rejected parts by increasing the tolerance zone. The bigger the hole gets, the more position tolerance it will get.

I wonder, how do these symbols help parts fit together? What is Bonus Tolerance? The values were reversed somehow from the perpendicularity page.

The default is always RFS. Each modifier or lack thereof provides its own benefits. Just know that if you come across the circle S, take your pen and cross right through it and it has the same meaning. It’s not the local size and it is not the actual mating envelope, it is the unrelated actual minimum material envelope.


But id you use LMC instead, if the hole gets bigger, you’ll have less positional bonus, and that’s the idea isn’t it? Out of which specified positional tolerance is 0.

Introduction to Bonus Tolerance

This does not work well when you are considering a pattern of holes that function together such as a bolt hole pattern We don’t want the OP to be confused thinking about “hole tolerance” as initially shown as a hole size tolerance, don’t we? In the above figure the size of the hole can vary from This ensures a bigger hole “stays” in place while smaller hole can “move around” like a planetary gear.

My original question If we have specified originally pos.

The question to ask yourself is: Download Now Defense manufacturing is all about project manufacturing and project accounting.

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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. Anyway, what really matters here is the inclusion of the M or Maximum Material Condition modifier in the feature control frame.