Results 1 to 4 of 4

Thread: True Position callout

  1. #1
    joshmxz
    Guest

    True Position callout

    I am wondering about a perticular True Position callout. The callout is TP .025 I understand this type of callout if there is bores below. for the features to be "inline" with eachother. in this perticular aplication, it is a set of 5 OD's on a polor radius equaly spaced.


  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
    Posts
    2,611
    Quote Originally Posted by joshmxz View Post
    I am wondering about a perticular True Position callout. The callout is TP .025 I understand this type of callout if there is bores below. for the features to be "inline" with eachother. in this perticular aplication, it is a set of 5 OD's on a polor radius equaly spaced.

    Ok, you have three separate positional requirements for a pattern of five features with size (FOS).
    MMC of the OD’s (outside diameters) should be 51.1

    The top feature control frame (FCF) specifies that the pattern of features have a true position of diametric tolerance boundary of 2.5 (mm) at MMC relative to datum’s A, B at MMB and Z.

    Where:
    MMC is Maximum Material Condition
    MMB is Maximum Material Boundary (size) of the datum feature.

    This is a separate requirement and measurement.

    --------------------------------------------------------------------------

    The middle feature control frame (FCF) specifies that the five FOS's have a true position requirement of diametric tolerance boundary of 0.13 (mm) at RFS relative to datum’s A, B at MMB.

    Where:
    RFS is Regardless of Feature size

    This is a separate requirement and measurement.

    --------------------------------------------------------------

    The bottom FCF specifies that the five FOS have a true position requirement of diametric tolerance boundary of 0.1 (mm) at RFS relative to EACH OTHER - no datum reference.

    This is a separate requirement or measurement.

    The affectivity is that you have five tolerance boundaries, diameter 0.1 located relative to each other at the specified basic (or Theoretically Exact) dimensions and the as-manufactured derived axis of the five OD's must fall within these tolerance boundaries simultaneously.

  3. #3
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,043
    OMG!! Even after reading Kelly's explanation I am completely bamboozled. A good thing I am retired and don't need to try and understand all this new fangled stuff!!

  4. #4
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Location
    Rochester Pennsylvania
    Posts
    396


    I'm with you on that Dave. Although the whole GD&T thing makes good global sense over the written word... When I get prints loaded with all that... uh, stuff ... It takes me a while to figure out what they're after. Usually have to pick up my book...

    Fortunately we don't run into much of it for most of what we manufacture where I'm at. Pretty basic stuff for the most part and we always convert customer prints over to our own style of prints for our floor. This way each operation always knows where to look on the prints for the information they need.

Posting Permissions

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