ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
(OP)
Good Afternoon,
[/indent]I have a part that does mount on two surfaces although the surfaces are perpendicular to one another. Datum A on my drawing is parallel to the to the X-Axis. Datum D is a plane perpendicular to the X-Axis. I then have 3 cylindrical holes and one slotted hole in line on the Z Axis running through the Datum A plane. One cylindrical hole is Datum B and the slot below it is Datum C. When I come to the feature control frames for the holes / slots it goes like this. True Position | Ø.2 | A – D | B | C |
[/indent]Planes A-D would make an line axis in the z direction? With datum B hole tie down the x direction rotation? With Datum C being the “Z” direction zero? I know that’s not right because all the drawing dimensions are coming the Datum B.
I cannot wrap my head around the reason the engineer did not believe it would flush up against datum A and then rotate to datum D and align to datum B.
I am looking at a drawing I clearly don't understand.
[/indent]I have a part that does mount on two surfaces although the surfaces are perpendicular to one another. Datum A on my drawing is parallel to the to the X-Axis. Datum D is a plane perpendicular to the X-Axis. I then have 3 cylindrical holes and one slotted hole in line on the Z Axis running through the Datum A plane. One cylindrical hole is Datum B and the slot below it is Datum C. When I come to the feature control frames for the holes / slots it goes like this. True Position | Ø.2 | A – D | B | C |
[/indent]Planes A-D would make an line axis in the z direction? With datum B hole tie down the x direction rotation? With Datum C being the “Z” direction zero? I know that’s not right because all the drawing dimensions are coming the Datum B.
I cannot wrap my head around the reason the engineer did not believe it would flush up against datum A and then rotate to datum D and align to datum B.





RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
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RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
Why? Since A and D are nominally perpendicular to each other, the question is which one is taking / removing the degrees of freedom and in what order or precedence? Sitting flush on A and also sitting flush on D in the same time? I am not sure how realistic din scenario is? Which is driving and which is driven?
What is the physical reality of this assembly? How this electronic case/ box is assembled?
I my opinion, but knowing nothing about this assembly, I would say that A primary, B secondary and C tertiary is more realistic approach.
Then D, as currently shown, should be profile to A, B, C (not to A-D, B, C)
Or even D primary, B secondary and C tertiary could be used as the global DRF for this assembly. Then maybe A should be profile to D, B and C.
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
RE: ISO GD&T Question concerning using two adjacent planes to create a primary datum on a non-cylind
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