Profile tolerance w/ reference datums dimensioned from non-datum edges?
Profile tolerance w/ reference datums dimensioned from non-datum edges?
(OP)
I'm inspecting a part which is toleranced in a way I have not encountered before. I believe the method used is incorrect, but I'd like a second opinion.

As you can see the untoleranced dimensions are basic, but they are not dimensioned from the datums called out in the profile tolerance FCF.
In this situation how would you apply the profile tolerance to the location of the two untoleranced holes?

As you can see the untoleranced dimensions are basic, but they are not dimensioned from the datums called out in the profile tolerance FCF.
In this situation how would you apply the profile tolerance to the location of the two untoleranced holes?





RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
Datum C is called up twice, which is wrong. Given that datum C is tertiary, only one slot should be a datum.
There is no dimension from the edge to the datum slots, and there is no positional tolerance on your holes. Maybe these are on another view on the drawing. Showing the dimension from the edge, rather than from the datum feature, is poor drafting practice, but it is not wrong. If there is a dimension from the slot to the edge, and there is a positional tolerance, you can inspect it. The positional tolerance works from the slot, not from the edge.
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JHG
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
I note that you have a default hole tolerance. Are they countersunk or centre bored? In the absence of a positional tolerance, your profile tolerance controls the position of the holes.
Yes, the profile tolerances work from the datums, not from the non-datum edge.
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JHG
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
Thanks
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
What I'm gearing at is: I don't necessarily know that a dimension without a direct tolerance applied to it is basic. I only know that it does not have a direct tolerance contained within the dimension value. With a small cutout from a print, I do not know whether there is more relevant information or not.
There's two interpretations I see:
1) Yours, if there is no other clarifying information, is correct
or
2) There may be a note somewhere clarifying the 'default' tolerances based on decimal points or 'size' of number, depending on how the company decided. In this case, "untoleranced" would only refer to those features which are not dimensioned, such as that curvy cutout in the middle, the length of the full-round slot, and the distance of the slot from the edge, which must be measured in regards to the datum alignment A|B|C, as specified., and the other dimensions are measured exactly as shown.
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
The only default tolerance information on the drawing is what is shown at the bottom of the image.
I did not include the entire drawing, the center feature is dimensioned elsewhere on the drawing, I simply provided this as a sample as the holes are the most obvious example on the drawing of a set of features with no tolerancing beyond the profile tolerance shown.
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?
Untoleranced
dimesnions
are basic:
RE: Profile tolerance w/ reference datums dimensioned from non-datum edges?