Selecting a Basic dimension as a datum
Selecting a Basic dimension as a datum
(OP)
I am working with a client that has placed a datum symbol on a basic dimension that has opposing elements. Is this standard compliant?
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Selecting a Basic dimension as a datum
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RE: Selecting a Basic dimension as a datum
RE: Selecting a Basic dimension as a datum
RE: Selecting a Basic dimension as a datum
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Selecting a Basic dimension as a datum
Your regular FOS is usually directly toleranced, and basic size has some geometrical tolerance attached to it. Either way some sort of LMB / MMB condition exists.
When it comes to reference dimension, I guess only RMB datum may be safely specified.
RE: Selecting a Basic dimension as a datum
dimension, reference: a dimension, usually without
a tolerance, that is used for informational purposes only.
NOTE: A reference dimension is a repeat of a dimension or is
derived from other values shown on the drawing or on related
drawings. It is considered auxiliary information and does not govern
production or inspection operations. See Figs. 1-19 and 1-20.
Where a basic dimension is repeated on a drawing, it need not be
identified as reference. For information on how to indicate a reference
dimension, see para 1.7.6.
1.4 FUNDAMENTAL RULES
(c) Each necessary dimension of an end product shall
be shown. No more dimensions than those necessary for
complete definition shall be given. The use of reference
dimensions on a drawing should be minimized.
RE: Selecting a Basic dimension as a datum
Frank
RE: Selecting a Basic dimension as a datum
Tunalover
RE: Selecting a Basic dimension as a datum
Frank
RE: Selecting a Basic dimension as a datum
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Selecting a Basic dimension as a datum
Maybe that is why the definition says: "a dimension, usually without a tolerance, that is used for informational purposes only."?
Of course one may imagine following situation:
So I enclosed a toleranced dimension within parentheses. This solves the problem of datum feature referencing at MMB or LMB for primary datum features. But what about secondary and/or tertiary datum features referenced at MMB/LMB? These MMBs/LMBs are usually generated not only by size tolerances, but also by geometric tolerances applied to these datum features (secondary DF is geometrically controlled to primary DF, tertiary to primary and secondary). Should I also make these tolerances reference in order to be able to calculate MMB/LMB of datum features properly?