Complex geometry, do my datums make sense?

[ETUDEN]

Hey there all,

I have a small casted part dimensioned in MM that I'm applying GD&T to. I have attached an initial drawing and would love feedback on whether my datums make sense. Specifically, on datum C, which I mean to define a mid-plane based on an isosceles trapezoidal feature. I've seen datums referenced off a conical feature, but do not know if I can apply the same line of thought to this drawing.

Thanks in advance for the replies!

 

[3DDave]

Sure. Not sure how the simulation will be done by your inspectors, but it is a legitimate use. (mm, not MM) Cones define 6 degrees of restraint. This will constrain 5.

 

[Belanger]

Hi Etuden -- Datum feature B is not identified anywhere. Also, you have to be careful with datum C, because the profile tolerance extends between X and Y. But according to your post, you don't want the middle portion (between the angled surfaces) to be part of datum feature C.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

The better choice is 4 target areas on the sloped surfaces and matching features on the mating part.

 

[Tarator]

ETUDEN,

- Datum feature B is missing.
- I think 0.15 flatness should be a Profile of a Surface, unless you do not care about coplanarity. Also, add 3X to the FCF. I would also remove the datum feature flag for A (no need since the 3 datum targets are very clear).
- It would be much better if you could show the mating part(s) so we can see how they assembly and have an idea about the function of this part. With that being said, I have a feeling that your datum feature C is not correct (regarding design intent). Also, because datum feature B is missing is very hard to analyze.