simultaneous requirement to parallelism?

[bxbzq]

Hi, please see attached. The question is, do the tolerance zones of the two surfaces specified by parallelism tolerance float simultaneously within 1mm size tolerance, or independently?

 

[bxbzq]

forgot attachment.

 

[pmarc]

Inpendently

 

[CheckerHater]

http://www.tec-ease.com/gdt-tips-view.php?q=194

 

[MechNorth]

CH has the right idea if you want to control coplanarity.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[bxbzq]

I was misled by 2 SURFACES note. The '94 std does define pattern. Even if the two surfaces are a pattern, they are not located by basic dimensions, so sim req't does not apply.

Side note: I read the standard again and noticed the word "located". So technically simultaneous requirements apply to Position, Profile and Runout. But in '94 standard, Runout is not mentioned.

4.5.12 Simultaneous Requirements.
Where two or more features or patterns of features are located by basic dimensions related to common datum features referenced in the same order of precedence and at the same material condition, as applicable, they are considered a composite pattern with the geometric tolerances applied simultaneously...


The '09 std explicitly states sim req't applies to Position and Profile tolerances.

I'm just writing down my thinking.