Datum surfaces not perpendicular?

[ImNotSure]

Ive been talking with the customer & they assure me its correct. Their datum surfaces are not perpendicular to each other & correct me if im wrong, but couldnt you "slide" along datum "A" and have the nominals change for the holes on datum D & E?

Or are the basics coming from the intersection of datum D/E & datum A?

Im sorry for the bad picture/drawing, Im a bit busy. Datum "A" is the top surface, where the basic 0.00 is called out in zone B8

 

[ImNotSure]

With out datum points on "A" I mean. The way I look at it is ultimately its 3,2,1

So for "D,A,C"

D is three points (easy)
A is two points (but where, at the intersection of D & A?)
C is one point (easy...)

 

[fsincox]

Those are technically datum features. Maybe I should not have said "datums", but, used the term "datum reference framework". I agree datum references can be on features that are not at 90 degrees from each other, The datum referecence framework, so established, will establish planes that are at 90 degrees, basic.
Frank

 

[btrueblood]

Frank, I agree with most of what you wrote. Took exception to this though:

"I prefer to give the benefit of the doubt to the engineer who should know this. "

I don't. Engineers should stick to the book unless they really KNOW they need to deviate, and then get an expert to give them advice. I'm probably like most mechies, in that my GDT training came on-the-job, and maybe an 8-hour class taught by a knowledgeable elder engineer. My only adder is that I have sat down and read thru the ANSI spec., in at least a couple of its versions.

Then read down the page to Imnotsure's comments about the GDT added "just for fun", and laughed.

 

[fsincox]

btrueblood,
Thanks, That is more of a personal choice in how I try to conduct my business. Not a requirement for anyone else. I was using the term "engineer" in the generic sense and should add: "who has the benifit of knowing the function of the part".
Frank

 

[btrueblood]

I know Frank, please read my posts as being written with tongue somewhat in cheek, and from the OEM not supplier side (you would be amazed, but then again likely not, at the number of engineers I have met that have never heard of GDT). But, if I were (for instance) a job-shop QC, I would have to take your attitude as well.

Imnotsure,

"D is three points (easy)
A is two points (but where, at the intersection of D & A?)
C is one point (easy...)"

Well, technically at the intersection of a perpendicular line (the dimension line if you will) drawn from A to where that perpendicular line intersects D - to establish the center of the holes.