hole patern used as Datum call out
hole patern used as Datum call out
(OP)
I am a Designer not Engineering and I would like to go back and let engineering know they are not correct. Am I the one that does not understand the standards? Can the center line of a hole patern be used as a datum call out? In this case Dia 4.750 was used as Datum B.





RE: hole patern used as Datum call out
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: hole patern used as Datum call out
RE: hole patern used as Datum call out
Read the paragraph don't just look at the figure.
You may be able to extrapolate from paragraph 4.5.8 how it might possibly be used on a bold circle, I'm not smart enough to do such things however
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: hole patern used as Datum call out
Having said that, I agree with Kenat about being skeptical of exactly how this has been called out. I'd prefer to see something that matched the spec example more closely (just because it's easier to point at and say 'this is what I/it means'), but I don't think the print you give is wrong relative to the standard.
All this assumes that you (and your engineers) are working to the Y14.5M-1994 standard - which is just a guess on my part, since I don't see a callout on the print.
RE: hole patern used as Datum call out
Yes we are working to the Y14.5M-1994 standards, just some misunderstand them and do not reason till proven wrong.
RE: hole patern used as Datum call out
KENAT is right, in Fig. 4-22 the pattern of 4 holes is the datum feature.
A fundamental concept of datum referencing in Y14.5 is that datums are defined in precise holding devices like plates and pins. In this case, the part would be held using a plate with 4 perfect pins that are on a perfect 4.750 circle. Datum axis B is at the center of the 4 pins.
A common approximation is to measure a best-fit circle on the 4 holes, find its center, and call that Datum B. This will get you close, but it doesn't follow the Y14.5 principle.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: hole patern used as Datum call out
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: hole patern used as Datum call out
"The datum feature symbol is applied to the feature surface outline, extension line, dimension line or feature control frame"
If the design intent is to make pattern of holes as a datum feature B, the most common way to place datum feature symbol (which is also very often presented in the standard) would be to attached it to FCF which is actually missing on this drawing.
RE: hole patern used as Datum call out
ex. |(┼)|Ø.007|A|B|
Sorry that was the only symbol that i could find that was close to a pos tolerance.
RE: hole patern used as Datum call out
Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion
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RE: hole patern used as Datum call out
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: hole patern used as Datum call out
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