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

Patterns as datums

Patterns as datums

Patterns as datums

While I can not find it in the ANSI Y14.5-1994 standard, I understand I can I use a pattern of holes as a datum simply by putting a datum symbol (a dash followed by the datum letter followed by another dash)  on the dimension and feature control frame for one of the holes.  Can anybody advise me on this.

RE: Patterns as datums

A pattern of holes CAN be specified as a datum feature.  The concept is described in ASME Y14.5M-1994, paragraph 4.5.8 as follows:

"4.5.8 Pattern of Features. Multiple features of size, such as a pattern of holes at MMC, may be used as a group to establish a datum when part function dictates. See Fig. 4-22. In this case, individual datum axes are established at the true position of
each hole. These are the axes of true cylinders that simulate the virtual condition of the holes. When the part is mounted on the primary datum surface, the pattern of holes establishes the second and third datum planes of the datum reference frame. Where the secondary datum feature is referenced at MMC in the feature control frame, the axis of the feature pattern established by all the holes may depart from the axis of the datum reference frame as the datum feature departs from MMC."

The method for identifying the pattern as a datum feature on the field of the drawing is specified in paragraph 3.4.6 as follows:

"3.4.6 Combined Feature Control Frame and Datum Feature Symbol. Where a feature or pattem of features controlled by a geometric tolerance also serves as a datum feature, the feature control frame and datum feature symbol are combined. See
Fig. 3-23. ....."

Of course, the viewing the figures referenced in the paragraphs will also help out a lot.  Hope this answers your questions.


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! Already a Member? Login


eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. Download Now
White Paper - Industry 4.0 and the Future of Engineering Education
With industries becoming more automated, more tech-driven and more complex, engineers need to keep their skills and knowledge up to date in order to stay on top of this wave—and to be prepared for the Industry 4.0 future. The University of Cincinnati offers two online Master of Engineering degree programs designed specifically for practicing engineers. Download Now
eBook - The Design Gridlock Manifesto
In this eBook, you’ll learn 6 ways old CAD technology slows your company down and hear how design teams have put those problems to rest. “The Design Gridlock Manifesto” shares first-hand modern CAD experiences from 15 companies around the world. Download Now
White Paper - Comparing Multi-Patterning at 5nm: SADP, SAQP, and SALELE
Self-aligned multi-patterning techniques such as SADP, SAQP, and SALELE are increasingly popular at advanced nodes, but each process has its pros and cons. IMEC and Mentor, a Siemens business collaborated to identify potentially less-obvious process and design limitations and trade-offs between the three SAMP techniques. Learn more in this paper. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close