Results 1 to 8 of 8

Thread: GD&T question

  1. #1
    Associate Engineer
    Join Date
    Sep 2013
    Posts
    3

    GD&T question

    VZW6KWA.jpg

    See picture above(which hopefully links)

    I'm trying to use GD&T to tolerance the flats of the D-hole. What I'm trying to describe is the flats centered on the 1.125 diameter hole.

    I also have to do something similar with the shaft that fits through this hole.

    Position tolerance I have doesn't feel right. What are your thoughts? Can you use symmetry in a hole?

    Thanks,
    Pete

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    2,611
    Try Profile of Surface - All Around...

  3. #3
    Associate Engineer
    Join Date
    Aug 2013
    Posts
    3
    your hole is not fully dimensioned.
    please give dimension from centre of hole and any one side of flat and make that dimension basic.
    by doing this your current position tolerance will serve your purp

  4. #4
    Associate Engineer
    Join Date
    Sep 2013
    Posts
    3
    Quote Originally Posted by Rahul_Kamdar View Post
    your hole is not fully dimensioned.
    please give dimension from centre of hole and any one side of flat and make that dimension basic.
    by doing this your current position tolerance will serve your purp
    I couldn't help but feel like I was missing something when I drew this last night. The drawing does seem more complete with that basic dimension added.

    Any other ideas before I close this out?

  5. #5
    Associate Engineer
    Join Date
    Sep 2013
    Posts
    3

  6. #6
    Project Engineer
    Join Date
    May 2011
    Location
    Michigan
    Posts
    78
    No... the .438 should not be basic. Basic dimensions establish the "basis" for a geometric tolerance. Your geometric tolerance is position. The only basic dims should be those that help establish position (location). If you were using profile of a surface across the two flats (or even all around), then that basic dim would be needed, and you'd drop any ± tolerances on the .875, because profile across there would be controlling size as well.

  7. #7
    Project Engineer
    Join Date
    May 2011
    Location
    Michigan
    Posts
    78
    To add to my last post...

    In case you're not aware, the position tolerance actually applies to the center plane of the two flats, not the flats themselves. This is why the basic dim of .438 shouldn't be there.

  8. #8
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    2,611
    On another look at the geometry it appears that it is punched sheet metal. This is because there are sharp corners designed into an internal cutout feature.

    Since the geometry will require a single action tool to create, Profile of Surface would reflect the best control.

    All of this assumes that this is in fact a sheet metal punched part.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •