Implied Flatness Ordinate Dimensions
Implied Flatness Ordinate Dimensions
(OP)
Does Implied flatness still apply to both surfaces when using ordinate dimensions, or does the side with the 0- denotation sort of become a datum and the flatness only applies to the non zero dimension?







RE: Implied Flatness Ordinate Dimensions
How you dimension it? with ±?
RE: Implied Flatness Ordinate Dimensions
it is dimensioned with block tolerances.
RE: Implied Flatness Ordinate Dimensions
You can use the origin symbol (per Y14.5) --so called poor man datum -- to show which surface is which.
RE: Implied Flatness Ordinate Dimensions
As a follow-up, where in ASME Y14.5 does it define implied flatness? Is implied flatness the keyword I should search for?
RE: Implied Flatness Ordinate Dimensions
Figure 2.5 in ASME Y14.5-2009 explains the origin symbol. I suggest you look at it.
--
JHG
RE: Implied Flatness Ordinate Dimensions
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: Implied Flatness Ordinate Dimensions
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Implied Flatness Ordinate Dimensions
Check the figure in the standard. In ASME Y14.5M-1994, it is figure 2.5 as well, but it is not as clear. The origin face works like a datum. Rule 1 does not apply here.
--
JHG
RE: Implied Flatness Ordinate Dimensions
I see what you're saying but there is no dimension origin symbol here. You're probably saying that since one surface is zero then it is, by default, the dimension origin. That might be the case but since no dimension origin symbol is present then it's still open to interpretation, in my opinion.
Besides that, I was really just answering his question on implied flatness. I figured he had heard of rule #1 at some point but just couldn't remember exactly how it was phrased, or the details.
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: Implied Flatness Ordinate Dimensions
Since there is no origin symbol, both sides are required to have the implied flatness?
RE: Implied Flatness Ordinate Dimensions
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Implied Flatness Ordinate Dimensions
Why the top side and not the bottom?
If origin symbol was used, flatness tolerance of the top side would be indirectly defined by +/-1 tolerance, so no additional flatness tolerance would be needed. However, nothing would control flatness of the bottom side in this case.
RE: Implied Flatness Ordinate Dimensions
You are correct I meant the bottom would need the flatness defined as the top would already have it defined.
RE: Implied Flatness Ordinate Dimensions
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems