Parallel Bar calibration
Close
Login to Your Account
Likes Likes:  0
Results 1 to 4 of 4
  1. #1
    Join Date
    Mar 2021
    Country
    UNITED STATES
    State/Province
    Georgia
    Posts
    2
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default Parallel Bar calibration

    Hello Metrology forum. I have a parallel bar calibration procedure question. My procedure states that “Flatness and parallelism shall be within 0.0002” in 10 inches”. I would like some input on how you guys interpret this. The way I interpret it is if I have a 30” bar the total allowable deviation should be ([30/10] x 0.0002”) or .0006” but never change more than 0.0002” in any 10 inch section? A colleague believes it means that it cannot deviate more than the 0.0002” stated maximum in any 10 inches but must also stay within 0.0002” over the entire length because it doesn’t state: 0.0002” per 10”. Thanks for any input on this.

  2. #2
    Join Date
    Jun 2011
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    245
    Post Thanks / Like
    Likes (Given)
    53
    Likes (Received)
    81

    Default

    I think you are right. Engineering means .0002”/10”. If the part was 30” and you wanted .0002” overall, you would have left it at that.

    Only wrinkle is Rule 1. If there is a size tolerance, form (flatness, parallelism) must be perfect at the max material condition (greatest size). So you are correct, the part could be out .0006” but not if you are at the top of the size tolerance.

  3. #3
    Join Date
    Mar 2021
    Country
    UNITED STATES
    State/Province
    Georgia
    Posts
    2
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    Thanks for the input Adam.

  4. #4
    Join Date
    May 2014
    Country
    UNITED STATES
    State/Province
    Massachusetts
    Posts
    151
    Post Thanks / Like
    Likes (Given)
    8
    Likes (Received)
    38

    Default

    [QUOTE=AdamC;3724406]I think you are right. Engineering means .0002”/10”. If the part was 30” and you wanted .0002” overall, you would have left it at that.

    It is worthy to note parallelism of a plane surface also controls flatness, the flatness (if not specified tighter) must be at least as close as the parallelism requirement, so, foe this case, “Parallelism shall be…” would have the same result as “”Flatness and parallelism shall…”

    I agree “…within 0.0002” in 10 inches” means a 30” long part must be within 0.0006” out (unless further constrained by a size tolerance)

    They may have intended differently, but that is not what they said. :-)


Tags for this Thread

Bookmarks

Posting Permissions

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