Profile To "A" Datum?

[Peter Warcholyk]

Good Morning To All,

I'm hoping that my attachment will "attach".

What I have is a part with the following alignment;
level to "A" surface, rotate "B" to "C" and origin on "B".
So far simple.

What I'm finding is that quite often I'll have a profile call out to one datum, i.e.,
|A|. The indicated surface in the attachment is not parallel to the "A" datum surface.
How do I properly report the profile points only to |A|, ignoring B & C?

Thanks in advance.

ZydecoPete

[Matthew D. Hoedeman]

I'll bet you money it is a lazy, good-for-nothing engineer's mistake.

Just report to all the datums.

[kbotta]

Not neccessarily a mistake. Might be the only requirement for the feature in question. Seeing as you have cad, I'd report the T-val...

If you did not have the cad...You would need basic dimensions to locate the tolerance zone, and offset to that.
kb

[Matthew D. Hoedeman]

BUT, if he is reporting the "T" value, he IS reporting to A-B-C, all 3 datums.

[#2#]

I am very tempted everytime I see a not quite perfect GD&T callout to just report "The callout is vague or incorrect - feature can not be measured" Of course doing so would probably shorten my employment so I give in and do the best I can.

Oh, and I don't have any suggestions for this particular problem.

Helpfull as always!

[Peter Warcholyk]

Only "A"

Hey Folks,

Thanks for the responses thus far.

I have been reporting out the "T" value. The problem being that the intent is that the variance in distance should only be relative to the datum "A" surface.

I'm not sure how to accomplish this without involving the other two datums.

Is this a "bogus" type of call-out??

Thanks for your time and patience.

ZydecoPete

[ag162]

With the alignment in respect to the Dats AB&C,, the T value is appropriate in relation to Dat A.

VP A.Gore

[Jan d.]

The call-out is valid and correct. If you use V4.1, it will be a breeze to evaluate. But make sure you reports min/max ONLY. Otherwise the PC-Demons will be upon you, see the following thread.

http://www.pcdmisforum.com/showthread.php?t=2210

Please be aware that Wilcox has confirmed a bug in V4.1 when you have composite or dual single segment call-outs. You can not enter those today!


Jan.

[layout tech]

Could the leader line be to the wrong surface?
The adjacent surface appears to be parallel to Datum A.

It is hard to tell with the part at that angle.

Oh well! Just a thought. Worth what it cost you at least.

[dccfreak]

The engineer is trying to control the perpendicularity of the surface in question to Datum A from what it looks like to me. Technically, what he has drawn could be correct, but, it isn't that easy to interpret once it gets to our side. The engineer probably should have laid a perp on there and been done with it. Unless it is a really tight tolerance and the average of creating a plane just wouldn't do. At any rate, I would just call it a plane and report the perpendicularity number back to A as your profile.

[Peter Warcholyk]

Note; The "profile" surface is not supposed to be perpendicular to the "A" surface.

It is actually on a slight angle.

Thanks for all your inputs.

ZydecoPete

[dccfreak]

Sorry about that. My mistake.

If that is the case, how about measuring as an angle to datum a, then calculating the deviaiton of the meas angle from nominal into inch decimal, then multiply by two to get your profile value?

Just another though from the dark depths of my mind.

[craiger_ny]

Would leveling to A than rotating appropriately to the feature in question then doing profile be a proper interpretation? If it were a keyway that is true positioned to a single datum such as a bore I'd set my level, rotate normal to the keyway's vector, translate to the bore and TP from there. Can you align to the feature itself while maintaining a proper level? Perhaps that might be a valid interpretation.

Craig

[cmmguy]

If the profile is called to only one datum then that means the other constraints are allowed to float. This allows you to remove the restraints of the rotation datum using "Best-Fit" and only restrain the Datum A degree of freedom.