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DatumTarget Points

Big John
Hello,

I have a question about dimensions and Target Points.
In the attachment I have made a very simple drawing with our problem.
It concerns dimension 9.2 ( General limits +/-0.5mm)
The product is a casting, so Target Points have been added.
A1, A2, A3, B1, B2 and C1 (I have only drawing datums B and C. Datums A are three points on the underside.)
There are also holes in the base with boxed dimensions and a True Position from A,B,C

Ok here is the question:
Is the dimension 9.2 to be measured from point C, or is it meant to be over the whole side.
I have taken the dimension from point C, because the side is casting. The Source Inspector wants it to be over the whole side.
I explained to him that this is not so because it is a casting. (If taken over the whole side, then dimension 9.2 is out of tol)
He said the holes are to the Datums A, B, C, as stated on the drawing, the 9.2 is over the whole side, not from C.

There is also a note stating: "Inspection must use the same set of datums as maching"

I cannot find a explanation in the ASME.

Who is correct?
Attached Files
  • The drawing file is barely legible so here's my best stab at it.
    Is this a second-op machined part, post-casting, pre-plate? Drawing notes 1 & 7 lead me to think this.
    You have machining datum targets which are temporary, Note 11 applies only to specific features on the print, not all dim's.
    As soon as the casting is cut to make the machined part, it seems all those casting & machining datum targets get cut away.
    Note 11 guides machinist on sequence of events for cutting targets away.

    The final part should be measured per the normal defined datums (Not the targets), as the datum targets will be cut away from casting upon conclusion of machining. The only exception is if Flag note 11 is beside the dimension, then the 3x "A" datum targets not machined, are to be used to level.

    Note 13 applies ONLY to Datum targets A1 - A6 (use the ones the machinist didn't cut off), from my interpretation. B and C datums and datum targets are not mentioned.
  • In AMSE Y14.5, it is stated that a Datum target is a specified point, line or area that is used to establish the datum.
    So in other words, if the drawing has a specific target area (by design) basic dimensions, then it is the datum.

  • The Source Inspector wants it to be over the whole side.
    I explained to him that this is not so because it is a casting. (If taken over the whole side, then dimension 9.2 is out of tol)


    I am sure is because the angle draft on the casting.
    Calling up datum targets. That way, everybody works off the same datums.
  • Hallo,
    Thanks to everyone for looking at my problem.
    @ Louisd, Datums B and C are still on the product, Both Datums B and C are targeted on a cast side, not a machined side.
    Datum set A is machined away (A1, A2, A3)
  • in reply to Big John
    ok, so I was wrong, datum targets apply!
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