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Government and Boss wants answers

 Haven't posted since I have become a member, mainly because I always seem to find my answer on older post. All except this one. My cmm wont give me a correct measurement. Its a poor musician who blames his instrument, I know, but follow me here. When I manually mike the distance, I get 13.38mm, which is out of tol. however when I run the part on the cmm, It measures 13.325, which is in tol. The Gov rejected 3 of our last 4 shipments because of this. The part is 99.9% dimensioned with profiles. Not all of the 100+dims are measureing this way, only about 7 of them. However, it is the same 7 dims involved with all the 3 shipments.

I also have a question on stacking profile tolerances, how does that work? Please find attached the section of print in question. Wish I could upload the rest but its gov stuff. Can anyone please help me? dont know how the posted pic got way up there but its the best i can do. can anyone help?
  • thanks for getting back to me. Yes, this is in reference to dim 12.24 and yes the "D" datum us the bottom flat. The profile tolerance is .18. However, for some odd reason, there is a profile tolerance of .26 that is associated with the profile of datum "D". Is this a stackable tolerance?


    No, D has a tolerance and the surface you are concerned with has a tolerance and they cannot be added in any way.
    As I noted above, the condition of D can have a significant effect on the location of that surface.
  • Yes, twisting/warp/bending could certainly affect that dimension.
    In the aerospace industry, many of the products we make are allowed a certain amount of pressure to be applied for inspection because of this type of problem. Typically, 5 lbs per linear foot of part.


    +1
    Usually, there is a Datum specified that one may "constrain" the part against.