×
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

Flatness measurement

Flatness measurement

Flatness measurement

(OP)
I am looking for a way to measure steel plates flatness. The plate is 3'X 5' and is approximately 2 inches thick. I believe that the plate is slightly concave on one side. Is there any instrument I can use to get an exact meamsurement? I have already used a a straight edge.

RE: Flatness measurement

Coordinate Measuring Machine (CMM)?

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Flatness measurement

What kind of accuracy do you need?
A straight edge is usually close enough for most purposes.  Right off you can check the standard under which the plate was ordered and see what is allowed dimension wise.
You can get very accurate measurements though it its usually less expensive to have the plate finished or purchased to  the desired dimensions.

Come back with a little more information as to the results you are expecting.

RE: Flatness measurement

You could use a optical level with a micrometer attachment.  The level is similar to a transit and is used to level machine bases such as large lathe beds.  Most are good to .001" at 100'.  You should be able to rent one at a local surveyor shop for about $35 a day.
They work by first leveling the level then aiming at a white faced venier scale at different points on the plate.  In your case I would probably do readings in a grid pattern then calculate the slope and surface contour.
These instruments are tricky to level the first few times but you should get plenty of practice after everyone and their brother kicks the tripod while trying to look thru it.  

I am going to assume this plate is evenly supported.

Barry1961

RE: Flatness measurement

Put the piece on a surface plate.  Mount a dial indicator on an arm with a base on the surface plate.  Move the indicator, or the piece.

RE: Flatness measurement

Your plate should meet ASME SA-20/ASTM A-20 for flatness. Make sure you read the entire paragraphs and do the rounding(the mill does). For this a straight edge and a taper gauge should be enough. If the plate is shy on one side-UT it for thickness A-20 again.

You can order plate to half tolerence. A good plate roll man/person(PC) can make it flatter.

RE: Flatness measurement

FrankSmith,
deanc is right.  I could also imagine that the pyramid builders would do it exactly the same way.  ASTM A6 has permissible plate waviness tolerance for structural grade plate.  ASTM A20 has tolerances for pressure vessel grade steels.

Steve Braune
Tank Industry Consultants
www.tankindustry.com

RE: Flatness measurement

Crap, 3 x 5 feet.  I saw inches before.

RE: Flatness measurement

Don't sweat it, Mint.  I've checked bigger parts than that on granite surface plates.    Either the surface plate/indicator or CMM will get the answers Frank needs if a straight edge and feelers aren't accurate enough.

Find a local Blanchard grinding job shop and have them sweep the part for you until you develop in-house inspection capabilities.  (Assuming they check flatness...)

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