Is the print correct?
Is the print correct?
(OP)
1.) Am I right saying this print is not correct?
Missing basic dimension for the positional callout.
"7.2.1.1 Dimensions for True Position.
Dimensions
used to locate true position shall be basic and defined in
accordance with para. 2.1.1.2."
2.) If they have used perpendicularity instead of position I guess would be okay.
Just please confirm.
Thank you
Missing basic dimension for the positional callout.
"7.2.1.1 Dimensions for True Position.
Dimensions
used to locate true position shall be basic and defined in
accordance with para. 2.1.1.2."
2.) If they have used perpendicularity instead of position I guess would be okay.
Just please confirm.
Thank you





RE: Is the print correct?
"Know the rules well, so you can break them effectively."
? Dalai Lama XIV
RE: Is the print correct?
Not sure on point 2 as position tol should be used to locate features of size per 14.5M-1994.
Unequal bilateral position tolerance might be what they really want but can't be sure from the info available.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Is the print correct?
Frank
RE: Is the print correct?
(ducking)
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Is the print correct?
Perpendicularity callout would be OK too, though such callout would only control orientation of hole's axis to A but not its location.
The other side of the story is +/- dimension in axial direction. Some would say it is acceptable. I am saying basic 0.750 dimension should be used, side of the rod assigned as datum feature B, and B reference added to the positional callout.
RE: Is the print correct?
Frank
RE: Is the print correct?
Frank
RE: Is the print correct?
mea culpa!
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Is the print correct?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Is the print correct?
I have changed the print per Pmarc and Jim's input. See revised sketch.
Since the intent is to control the hole more relaxed in the left-right direction and more tight 90 degrees from this direction, do I need to have diametral symbol Ø ?
On both callouts?
On neither callouts?
Another question would be: if I use perpendicularity instead of the SECOND positional callout (first callout stay as is) the effect is the same or not?
Thank you again
RE: Is the print correct?
Yes, perpendicularity in the 2nd callout is the same -- and actually it is the correct symbol to use there. (Don't start me on this, guys!)
Finally, an aside to the group here: While it is legal, I often wonder if it's impractical to have a primary datum referenced with the "M" modifier when the secondary datum is a plane. This is because any looseness around A will allow the part to flatten out on B, thus making it the primary datum at times. I know it's OK to do it -- the new standard made a point of showing this option in Fig. 4-21(d) as well as Fig. 7-59 (although no text is given to explain it), but I'm just thinking about how the contact points affects the datum precedence.
Frankly, Greenimi, in many ways I vote for your first picture. :)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Is the print correct?
Frank
RE: Is the print correct?
RE: Is the print correct?
Perpendicularity to A in the second callout is not the same as position to A. Of course tt can be used as long as one realizes that the perpendicularity will not control the intersect of the axis of the toleranced hole and the datum axis A (shown in section B-B) but only their angular relationship. Position will do both.
RE: Is the print correct?
The way you have it now, you need diameter symbols for both callouts. This will create one cylindrical tolerance zone (wrt A) floating withing larger cylindrical tolerance zone (wrt A & B).
There is also another way you may want to consider which is shown in fig. 7-28 of Y14.5-2009 - bidirectional positional tolerancing, means 2 separate callouts without diameter symbol, creating rather rectangular tolerance zone. It is up to you and your functional requirements to choose the right method.
RE: Is the print correct?
Perpendicularity could be used in the second FCF - ONLY IF - you don't want the location of the hole wrt the Datum-A axis refined tigher than the .030 tolerance. It was my understanding that you wanted it tightened in this direction.
J-P, we (Tec-Ease) discuss with our students the issue of datum modifiers wrt datum precedence. It seems that it is a major eye-opener even to many long-certified GDTP's. We don't tell people not to do it, but do advise them to check the potential for datum precedence violation if the tolerances are generous.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Is the print correct?
Frank
RE: Is the print correct?
pmarc (and Jim) ... thanks for setting me straight on the lower frame and perpendicularity. I wasn't paying attention to the location of the hole across the shaft (doh!) since I was so preoccupied with the perpendicular aspect. My bad.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Is the print correct?
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Is the print correct?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Is the print correct?
I have revised the sketch per your latest comments (to have it for reference on future posts/readings).
The only thing, that might get in the way of using your advice (and change the actual print) is that now we need 2 gages to verify the positional requirements.--one to qualify Ø.030 and one to verify Ø.005.
Again, thank you for your guidance. Nice we have this place where we can learn from each other this "language" and apply GD&T in a correct and unambiguous way.
RE: Is the print correct?
Frank