True Position and MMC (Dilemma Between Engineers)

M

Maxebolo

Hi guys,
there is dilemma going on within our organization related to true position and MMC
please see attached file.
 

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  • True position on Hole (2).pdf
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Michael_M

Trusted Information Resource
Re: TRUE POSITION(DILEMMA BETWEEN ENGINEERS)

I just did a quick read over and on #5, the way I am reading it, one person is saying you have .030 true position with a bonus of .007 making the true position .037.

This would be incorrect. The diameter used has a total tolerance of +.006/-.000 so the MAX bonus tolerance (from 'B' which I am seeing as 'E') would be .006 if the actual hole diameter was .381000.

I am having a hard time reading the rest of it so will let others address it if they can get a better interruption then I have.
 
C

Curtis317

I have not dealt with GD&T a lot but Max Material Condition would make me think that it is smallest hole. LMC would relate to the material when the hole is at it largest. Let me know if I am incorrect
 

Michael_M

Trusted Information Resource
I have not dealt with GD&T a lot but Max Material Condition would make me think that it is smallest hole. LMC would relate to the material when the hole is at it largest. Let me know if I am incorrect


Max and least material depends on what you are measuring.

Max material condition is used on a hole. If you have a hole that is 1.000 +/-.005 andthe actual diameter of the hole is .995, you gain no bonus as the diameter is at the smallest size. In other words, you have less room for fit error. If the hole diameter is at 1.005 then you gain a bonus of .010 as the hole is at the highest diameter possible.

Least material condition is used on a boss. If you have a boss that is .990 +/-.005 and the actual diameter of the boss is .995, this would gain you 0 bonus tolerance as the diameter of the boss is at the highest possible. If the boss were to actually measure .985 you would gain .010.

Using the two examples above, assuming the boss is going to 'fit' into the hole. If both diameters gain you 0 bonus then you have to put the hole and the boss in exactly the right position otherwise they will not fit into each other. If you make the hole big and the boss small (but within tolerance) you have more room to 'misplace' the hole and/or boss before they will not slide into each other.
 
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