×
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 Annotation

Symmetry Annotation

Symmetry Annotation

(OP)
Hi,

I'm working on some drawings (making new drawings for reference) for a steel arch bridge built back in 1893, and have some of the original shop drawings.

On some of the drawings only one-half of the part is drawn (up to the Centerline) and noted: "SYM ABT CENTERLINE".

Am I right in assuming this means symmetrical about centerline, if so is this annotation still used today?, if not what else would be used.

Many thanks,

Gord

RE: Symmetry Annotation

I think you are safe in your assumption, it was common in the pre CAD days to have shortcuts like this in drafting practices. I was taught not to use section lines in my early career before we had modern CAD systems. The ASME standard fig. 1-33 shows a method for implying symmetry and I have heard it mentioned here before, but, I have never seen it used on a modern drawing.

RE: Symmetry Annotation

Hi Bridgenut

Yes your assumption is correct and I have recently seen CAD drawings using the same terms.

desertfox

RE: Symmetry Annotation

There is a GD&T symbol for symmetry as I recall though I believe it has wider application in ISO rather than ASME.

What you're talking about is subtly different but I think the idea is still shown in the relevant ASME spec whose number escapes me and I'm not at work to look.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Symmetry Annotation

I don't think the note is implying any GD&T constraint, simply that only half the bridge is drawn and the undrawn portion is a mirror image of the drawn portion.

My CAD system will make a half view and place 2 parallel lines at either end of a symmetry line per either ISO or ASME.  I don't know which specific parts of the standards cover this.

RE: Symmetry Annotation

dgallup,
Y14.5M-1994 shows what you have described in the figure per my above statement.
Frank

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