×
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

datum set on mounting surface of linear motion guide

datum set on mounting surface of linear motion guide

datum set on mounting surface of linear motion guide

(OP)
Hi,
Our linear rail assembly scheme is like attached. Now I need to figure out proper datum set. From assembly process standpoint, the shoulder should be specified as secondary datum. But the whole assembly (not shown here) is almost symmetrical about the center line derived from two lines of threaded holes which are used to fix the rails, while the shoulder is one of the non-symmetrical features. So naturally assigning the center line as secondary datum is straightforward and creates no confusion. I would like to hear opinions from others.
If the description does not give sufficient info, I'll try to post the drawing.

RE: datum set on mounting surface of linear motion guide

Threaded hole by itself is not the best choice for datum feature.
Deriving imaginary center plane from the whole bunch of threaded holes can make many people uncomfortable.
As a matter of personal opinion I would go with the shoulder. It's functional physical feature that's easy to deal with from machining and QC perspectives as well.

RE: datum set on mounting surface of linear motion guide

The shoulder is by design the secondary datum in your example, that is it's function, dimension it basic any way you want but the shoulder is the secondary datum reference surface. I have worked wit these before and did it the same way.
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