×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Symmetry and Concetricity without MMC or LMC

Symmetry and Concetricity without MMC or LMC

Symmetry and Concetricity without MMC or LMC

(OP)
Hi all,
Pardon me for asking this stupid question. Why Symmetry and Concentricity are used with only RFS?

RE: Symmetry and Concetricity without MMC or LMC

According to Y14.5-1994 or 2009 symmetry and concentricity (and runout) is by definition applicable on an RFS/RMB basis only, both for the considered feature and for the datum references respectively.

On ISO (GPS) I don't know, but I am sure other folks around will provide you an answer from ISO(GPS) perspective.

RE: Symmetry and Concetricity without MMC or LMC

The standard being used is of utmost importance to answering the question, but I presume ASME here, because that it where RFS/RMB is an absolute must with these symbols.

The main reason is that the very definition of concentricity and symmetry involves the "median points" of opposing elements. And the only way to find the median points is to take the actual elements from the actual surface, regardless of size. (If we were to take the median points of an envelope, such as that created by MMC, it would negate the definition of the symbol.)

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources