A real head-scratcher: 'As-Cast' and 'As-Machined' drawings and TP with a datum feature of size
A real head-scratcher: 'As-Cast' and 'As-Machined' drawings and TP with a datum feature of size
(OP)
Note — some dimensions and GD&T callouts that are likely irrelevant to discussion aren't depicted in my mocked-up illustration. I'm fairly new to GD&T— I've learned what I know online (often trolling here — thanks for all the help!) and from our senior engineers when they have a spare minute. On to my quandry (please refer to attached mockup illustration):
respect to the material boundaries of the bosses through which they're respectively drilled?
This one has been a real head-scratcher for me. I'd appreciate any feedback you folks can give me.
- 'A' is a datum feature of size — for better & for worse, this is a hard constraint. I promise that we had reasons for this
. - The 2x through holes have to be machined in a downstream operation controlled with its own dedicated machining drawing.
- I only care about controlling the true position of the holes with respect to the square bosses' boundaries (please refer to image),
i.e., holes can't encroach too close to either 'left/right' boundaries of the boss through which they're drilled. - <I think> I can rule out using one of the 'flange' faces as a primary datum feature in the machining drawing, as our casting datum feature 'A' is a feature of size – controlling left and right holes' positions via TP to a flange face
would not satisfy the previous requirement, as the holes have the original feature of size between them.
respect to the material boundaries of the bosses through which they're respectively drilled?
This one has been a real head-scratcher for me. I'd appreciate any feedback you folks can give me.





RE: A real head-scratcher: 'As-Cast' and 'As-Machined' drawings and TP with a datum feature of size
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: A real head-scratcher: 'As-Cast' and 'As-Machined' drawings and TP with a datum feature of size
Just make each face vertical (in this particular image) a FOS datum with an RFS reference to it; this will allow each hole to be nominally centered vertically; Might as well use each initial penetrating face as the primary for each hole.
I can't say about side-to-side control as the goal in that direction is unclear.