Position tolerance, Double-D Hole
Position tolerance, Double-D Hole
(OP)

See picture above(which hopefully posts)
I'm trying to use GD&T (Y14.5-2009) to tolerance the flats of the D-hole. What I'm trying to describe is the flats centered on the 1.125 diameter hole.
I also have to do something similar with the shaft that fits through this hole.
Position tolerance I have doesn't feel quite right. What are your thoughts?
Thanks,
Pete
(apologies to those who've seen this in a different (wrong) section of the forum.)





RE: Position tolerance, Double-D Hole
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
You already have a control on parallelism of the straight edges to -B- from it being referenced in the position fcf for the .875 width.
Also as I said before .438 is not essential.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Position tolerance, Double-D Hole
As it was mentioned, basic .438 is not needed.
Additionally diameter symbol preceding tolerance value in positional FCF for 1.125 diameter is missing.
You should also consider applying two perpendicularity tolerances controlling mutual relationship between datum features A, B and C:
1) for datum feature B - perpendicularity to |A|;
2) for datum feature C - perpendicularity to |A|B|.
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
Frank
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
However, using size tolerance to control flatness of ONE particular side you have chosen to be your datum feature introduces some ambiguity, don't you think?
RE: Position tolerance, Double-D Hole
If we assume for a moment that tolerance for .125 dimension is let's say +/-.005, allowable flatness tolerance for both sides of the plate will be .010.
What is ambiguous with that?
RE: Position tolerance, Double-D Hole
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
I am just trying to say, that you have to assume the worst, unless you actually specify flatness for one side.
Now the question is "which side?" We have symmetrical part that can be flipped over.
According to another fun paragraph, 4.8, we may have to add identifying feature to tell one from another. Good thing is we "may", not "shall", but I feel slightly uncomfortable adding non-functional feature just to satisfy requirements of the drafting standard.
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
Frank
RE: Position tolerance, Double-D Hole
I once asked 10 different inspectors: "For a simple rectangular block, where bottom face is datum feature A and flatness FCF controls its form, how would you verify this requirement?" You know how many answered something like: "You put the part on a base plate upside down, probe the datum feature with a height gage, and report the absolute value of indicator reading"? 8 of them.
This really is a problem out there in the real world.
RE: Position tolerance, Double-D Hole
I think that is OK as long as it is good, right?
Frank
RE: Position tolerance, Double-D Hole
RE: Position tolerance, Double-D Hole
Frank
RE: Position tolerance, Double-D Hole
The inspection method described unnecessarily verifies parallelism - that is first thing. Second, it is not able to extract actual flatness error from this check.
RE: Position tolerance, Double-D Hole