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Question meaning of dimension and how to measure

Question meaning of dimension and how to measure

Question meaning of dimension and how to measure

(OP)
The attached image represents a generic question relative to dimensioning and measuring a part.  Given a "U" shaped part, where the width between the two vertical legs of the "U" is dimensioned, and each leg of the "U" has an angular tolerance where is it appropriate to measure the dimension between the vertical legs?

The attached picture does a much better job of describing my question.

-Mike

RE: Question meaning of dimension and how to measure

(OP)
Thanks for the response!

What if both angles measure 91 degrees?  Obviously the dimension at B would be larger in this senario.  Don't I get all (3) of the tolerances to work with?

-Mike

 

RE: Question meaning of dimension and how to measure

(OP)
Thanks again KENAT...ANSI Y14.5.

RE: Question meaning of dimension and how to measure

OK, so the linear dimension is controlling the distance between the 2 sides and because of 'rule 1' it is also controlling parallelism of those 2 sides to each other to within the tolerance.

The angular dimensions are controlling the perpendicularity to the base.  It almost looks like you don't need both angular tolerances but at extremes of the linear tolerance both could come into play.

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RE: Question meaning of dimension and how to measure

Linear dimension prevents both faces to be inclined to each other in opposite direction at greater than a certain angle. This certain angle depends on the linear dimension tolerance.    

RE: Question meaning of dimension and how to measure

This may be a good case for a restraint note.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Question meaning of dimension and how to measure

All 3 conditions must be met for part acceptance.  Picture the FOS being at max'm (2.03), then you can't have +1 degree on either of the legs, but you may be able to have -1 deg (don't have the leg lengths so haven't done the math to see).  Not an uncommon situation.  May have been better defined with a datum and some perpendicularity controls.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: Question meaning of dimension and how to measure

If the size is at its maximum, you can't have both legs be at +1º but I would say that you can have one of the legs be +1º and also have the other leg at -1º.  This is because there is no Rule #1 type of relationship between size and orientation.   

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

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