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


.006mm flatness

.006mm flatness

.006mm flatness

I have a part that has a flatness call out of .0002in to itself and a .002in perpendicularity to datum A over the surface of a slot that measures .275in x .551in x .039in deep. Our customer says that the flatness is out by +.0002. I have tried to repeat that but I am having trouble with setting this up and to be able to check the flatness of this feature to itself. The perpendicularity to datum A is is good with in .0005 - .001 depending on the part. does anyone have any suggestions to help me out?

Thank You

Stephen Farrell
Quality Manager

RE: .006mm flatness

Isn't perpendicularity typically called out as an angle? Is your definition tied to a measurement of runout over a distance to get the angle?

What is your question? Are you wanting help on how to make the measurement? Have you looked at a non-contact profilometer?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: .006mm flatness

We have many small surfaces that have to be flat to a micron or two. We measure flatness using a Mahr Perthometer. You trace the surface in question then level the trace and pick the high and low points to find the flatness. It's really quite simple.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: .006mm flatness


Check out dgallup's reply. If you have a computerized device that can probe or scan a surface, then the flatness is just an absolute-value comparison of the high points and low points (peaks and valleys). It is not centered around anything, so there is no positive or negative connotation to the flatness reading. And there's no datum for flatness, so it ignores any tilt of the surface.

If you're stuck with more primitive inspection equipment, then flatness might be measured with a dial indicator, but since you said .0002 I hope you have a CMM or profilometer or perthometer (never hear of that one; it must be Mahr's trademark name).

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

RE: .006mm flatness

Thank you Belanger and dgallup for your input that's exactly what I thought. With our CMM and dial indicator I get the part good by aligning the part off that surface and probing it. I will have to get with our customer and see what method of inspection they are using I have a feeling its just visual. But again Thank You i just needed to know that what I was doing was the best way.

Thank You

Stephen Farrell
Quality Manager

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!


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