I need help with a dimension of MMC of .000 3

[moldshields]

1. The Drill Hole Dimension is - .448/.406 Dia. With GD&T Applied as followed;
True position| within a Diameter of .000 MMC| Datum A| Datum B MMC
My answer since we have a MMC of .000 for the Hole is .406 Dia.
Y/N
I got a reply for this stating “this feature, using a tolerance of .000 MMC, must be calculated based upon the .448/.406 Dia., AND using the “M” modifier, anything other than a result of .000 M is Variant”
Can someone please explain this? And are my numbers correct?
2. The Drill Hole Dimension is - .52/.44 Dia. With GD&T Applied as followed;
True position| within a Diameter of .010 MMC| Datum A
My answer since we have a MMC of .0101 for the Hole is .430 Dia.
Y/N
Thank you,
R. Phillips

 

[PeterStock]

I get nothing from your link. But the answers you give are correct for the virtual condition of the holes. I do not know what the reply is for. Were you taking some sort of automated test and if so what test?

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

 

[DesignBiz]

I could not see any graphics for your postsing as well.

As Peter mentions above your values are correct for the hole's virtual size. This would be the pin size in a hard gage to verify the hole location.

"My answer since we have a MMC of .0101 for the Hole is .430 Dia."
This is not a true statement. The MMC for a cylindrical hole is its minimum size; in this case .44" dia. The virtual size would be the MMC (.44"dia) minus the positional tolerance; would be .430"dia. This again would be the pin size in a hard gage to check the hole location.



"I got a reply for this stating "this feature, using a tolerance of .000 MMC, must be calculated based upon the .448/.406 Dia., AND using the "M" modifier, anything other than a result of .000 M is Variant"
My interpretation of response:
At the hole minimum size (.406"dia) it has a locational tolerance of "0". It would need to be perfect form and location at MMC. As the hole is manufactured larger within its size limits, then this deviation from the mmc would be allowable tolerance for location. (e.g. if the hole is measured to be .416" dia, the an allowable .010"dia tolerance zone for location is allowed. If .448"dia, then a .042"dia tolerance zone for location is permissible.

DesignBiz

 

[moldshields]

Thank you very much DesignBiz, apparently I need some sort of a cad file for you to review my images. Sorry about that. I agree with you for the .448"dia. with a .042" tolerance zone. This was my initial response to item #1. And I really appreciate your interpretation of the statment, let me see how should I repond to the government engineers about this. As for your reply to item #2? your saying that the hole is basically a .44"dia?

I really apprecite all the quick and professional feedback I am recieving. This is better than Dell's Tech Support!

 

[SeasonLee]

Moldshields

Item 1
Position tolerance is zero so the virtual size equals to MMC hole size=Ø.406.
The max bonus tolerance is the difference of hole size=Ø.448-Ø.406=Ø.042

How about your datum B? What’s the size of datum B? There is an additional datum shift (datum movement) for MMC on datum B, it will make some reject part (calculated by the allowable position tolerance) acceptable.

Item 2
LMC=Ø.52, MMC=Ø.44
Virtual size=MMC - position tolerance=Ø.44 - Ø.010=Ø.430
Max bonus=Ø.52-Ø.44=Ø.080

SeasonLee

 

[DesignBiz]

Moldshields,
A “basic” hole size would be a numerical value diameter in a box. This would be a “theroretical”exact size that you might see in description of a shape with a profile callout giving the tolerance.

For #2 hole; .44”dia is the smallest diameter for this hole’s size limits, thus it is the minimum hole size which is the MMC (maximum material condition for an internal feature of size). For the sake of argument, had this diameter been a boss instead of a hole, then the opposite is true; .52” diameter would be the MMC for an external feature of size. The MMC condition is the largest part size allowable while considering the dimensional limits of size. Sometimes I tell people to think of MMC as the heaviest part, with all of the external features as large as possible, while the internal features are as small as possible. LMC (least material condition) is the opposite of MMC.
The .44”dia in this case is the MMC (maximum material condition) for that hole”

The “virtual condition” according to the standard (pg. 4 para. 1.3.37) is:
“A constant boundary generated by the collective effects of a size feature’s specified MMC or LMC material condition and the geometric tolerance for that material condition." (See figs. pg 32 and 33). SeasonLee demonstrates this in a formula above.

Hope this helps and you are quite right that this a valuable webstite to help us refine our GD&T knowledge.


DesignBiz

 

[moldshields]

Thank you very much DesignBiz. Yes is really helped a lot.

 

[DesignBiz]

My pleasure Moldshields, if I along with others can be of help.

DesignBiz