True Position of slot Boundary with MMC

N

newbie23

#1
Hi Folks,

Please help. There're 3 slots ( .190+.002 -0 width and .375+/-.005 in length) 120 degrees apart with .001 MMC call out (detail B)

How do I apply the MMC for Positon Tolerance? Thanks.
 

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Michael_M

Trusted Information Resource
#2
The call out is to -A- and -B-. -B- is the 11.00 bolt circle so your position must be taken from that feature. How you add MMC is based on the .375 tolerance. If the .375 width dimension; for example .375 +/-.005 then you subtract what your actual dimension is from .370 and add this to the .001.

For example, the three slots are .374, .3745, and .375. For the first slot, you get .004 bonus (.374-.370=.004) making your true position .005 (.004 + .001 = .005) to the center of the slot. As indicated above, you will need to do the math for each slot as each can give you different bonuses.

Your true position only takes into account the 11.000 basic. The 30 degree basic dimension defines all other positions since the tolerance block of the slot does not account for a 3rd position (i.e. -C-).
 

Paul F. Jackson

Quite Involved in Discussions
#4
is the OD. [C] is the three slots and the position callout is associated with the slot-width only so the slot length is not controlled by the position note. [C] is a pattern of three slots that stop rotation for the coordinate system [A|B|C]. If you are checking the callout without hard gaging you would need to find the best rotation that fits all three slots simultaneously first without MMC then adjust the rotation to minimize the position error with respect to each slot's size. Typically the slot closest to the fitted 120 degree spacing center lines in the CW and CCW directions will provide the best fit but MMC allowances will frustrate that strategy.

If you do use an attribute gage diameter must be referenced RFS.
Paul
 
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