Tertiary datum on Drawing
Tertiary datum on Drawing
(OP)
I have attached drawing which contains GD & T callout. Two datum are used in the drawing to constrain part, however only 5 degrees of freedom is constrained part may still rotate. Since part is free to rotate it will not have any impact on GD&T callouts?





RE: Tertiary datum on Drawing
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Tertiary datum on Drawing
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Tertiary datum on Drawing
Actually, no! There is no problem rotating the part. This ceases to be true if you add any features not concentric with the hole.
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JHG
RE: Tertiary datum on Drawing
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JHG
RE: Tertiary datum on Drawing
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Tertiary datum on Drawing
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Tertiary datum on Drawing
Rotation implies some sort of an angle. Which angle in this case is controlled by Profile tolerance?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Tertiary datum on Drawing
What for? Implied 90 deg. angles and Sim. requirements are keeping the pieces together.
See ASME 14.5-2009 Fig. 4-39
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Tertiary datum on Drawing
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Tertiary datum on Drawing
Which brings interesting afterthought: there is no such thing like implied horizontal (or vertical) line. We take for granted that certain edges of the part are (arbitrarily) made parallel to the edges of drawing sheet, but it is merely a matter of convenience.
What if you are trying to make a sketch on a piece of paper that is not rectangular at all? Could anyone reference the rule that makes the view on the right of enclosed picture "illegal"? No, seriously.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future