dimensions from Datums
dimensions from Datums
(OP)
This is so basic I feel shameful but there is a big debate at work right now.
Incase the attachment doesnt work, the picture shows a blob with a Profile tolerance of .5 all around it constrained to a parrallel datum A only. one of the surfaces of the blob is Datum B with a 2.5" basic dimension comming off to show the overall height of the blob.
Group 1, thinks the MMC of the 2.5 is 3.0 LMC is 2.0
Group 2, thinks the MMC is 2.75 and the LMC is 2.25 (because you get not profile tolerance on if off the datum surface
Group 3, thinks the 2.5 is unrelated to the .5 profile because it goes to datum B and therefore falls with the overall profile tolerance of the drawing.
Any help? Sorry this is so easy but when we looked though all the Tec-Ease Books almost all the examples go to holes and don't really deal with MMC of a linear dimension off a datum.
Incase the attachment doesnt work, the picture shows a blob with a Profile tolerance of .5 all around it constrained to a parrallel datum A only. one of the surfaces of the blob is Datum B with a 2.5" basic dimension comming off to show the overall height of the blob.
Group 1, thinks the MMC of the 2.5 is 3.0 LMC is 2.0
Group 2, thinks the MMC is 2.75 and the LMC is 2.25 (because you get not profile tolerance on if off the datum surface
Group 3, thinks the 2.5 is unrelated to the .5 profile because it goes to datum B and therefore falls with the overall profile tolerance of the drawing.
Any help? Sorry this is so easy but when we looked though all the Tec-Ease Books almost all the examples go to holes and don't really deal with MMC of a linear dimension off a datum.





RE: dimensions from Datums
RE: dimensions from Datums
RE: dimensions from Datums
RE: dimensions from Datums
RE: dimensions from Datums
RE: dimensions from Datums
I would agree with group 1 for a width dimension. One end of the height is datum B, which is correct by definition. The maximum error all is at the top. I go with group 2.
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JHG
RE: dimensions from Datums
Parts made from soft silicon is a nonrigit parts, I think you need to add a restraint note on the drawing to describe the clamp conditions during inspection.
Season
RE: dimensions from Datums
Two key factors, as pmarc pointed out:
-- the profile tolerance of 0.5 does NOT reference datum B, so that bottom datum is irrelevant to the question.
-- the profile tolerance of 0.5 is all around, so the 0.25 general profile tolerance is irrelevant to the question.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: dimensions from Datums
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
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