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  • anti - bonus tolerance GD&T

    Discussion in 'The main mechanical design forum' started by maniacal_engineer, Apr 28, 2011.

    1. maniacal_engineer

      maniacal_engineer Well-Known Member

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      In GD&T there is the concept of bonus tolerance - the idea that as a feature of size deviates from MMC that it can be less perfect in placement or form. I am making a fixture type thing - a slot that holds a part centered - and would like to do the opposite. In other words if the slot is narrow (MMC) it can float around more, but as the slot widens and the mating part gets sloppier in the slot, then the slot position tolerance would need to get tighter.

      How would this be done? If I just use LMC modifier will that do it?
       
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    3. jthornburgh

      jthornburgh Member

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      yes that would be LMC
       
    4. maniacal_engineer

      maniacal_engineer Well-Known Member

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      Thanks

      I have taken GD&T classes, but haven't used some of the techniques for a while so I am a little rusty in some areas.
       
    5. doctorx

      doctorx New Member

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      Don't think of it as anti-bonus. Bonus tolerance and the material conditions are framed the way they are for such fit issues. Think of the bonus being at the opposite condition of that specified.
       
    6. QuickTol

      QuickTol Member

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      Old post, but for those who read this later: It is called LMC (Least Material Condition). As the feature deviates from MMC, it is permitted more tolerance. LMC is typically used to maximize wall thicknesses, whereas MMC is used to promote fix.
       

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