Question on BASIC dimensions

[d.evans]

I have a drawing for a part that is a metal tube with a hole cut straight thru the side of the tube. You end up with a sort of a "shark-bite" looking tube. Now, turning the tube over so that you are looking at it from the side, 90 deg perpendicular to the hole thru the side, you are left with an hourglass-shaped part. NOW...the hourglass-looking features have a profile callout. That's OK. What I don't get is all the basic dimensions defining where along the tube the hole is located, the 'angle' of the hourglass cutout etc. What tolerance do I use for the 90 degree angle of the cutout, the overall diameter, the starting-point location?
(The profile tol is .010")
Help! jpegs attached
I just read 2.12 of the Y14.5 1994, and it addresses this issue. I'm now wondering if I even need to worry about these callouts.??

[VONDY]

RE

IT WOULD BE NICE TO SEE MORE OF THE PRINT DEFINING DATUMS -A-B-C-

[Roger Kilpatrick]

As I see it you have NO tolerance on anything except the profile, none of the basic dim's seem to have a feature control frame, therefore I would tolerance it per print, +/- .0000000 and let someone figure out how to build it per the engineers design.

[VONDY]

RE

OTHER VIEWS OF THE PRINT MAY SHOW MORE THAN WHAT THIS VIEW IS TELLING US

[d.evans]

sorry, here's more dwg

Thanks for the quick responses.

[VONDY]

IN MY OPINION, THE THROUGH HOLE IS CONTROLLED BY THE DIAMETER TOLERANCE AND T.P. CALL OUT TO -A-B-. ALL THE OTHER BASIC DIMENSIONS TO ME SHOULD BE "REFERENCE" INSTEAD OF "BASIC". THEY ALL ARE AFFECTED BY THAT THROUGH HOLE AND ARE DEPENDANT ON IT AND ITS LOCATION. I WOULD HAVE ENGINEERING REMOVED THEM IF THEY WILL ALLOW IT.

[John Kingston]

The other basic dimensions are controlling the profile of the cutout. they are looking for form and location of the cutout. I could be misinterpreting it, but kbotta will surely have a clear answer. He usually signs in during the early AM hours.

[kbotta]

If I am looking at this correctly (I think I am) The primary is the 'stock' (OD)tube? And the 2ndary is a planar end of the tube. Is there no tertiary to stop the rotation about the primary axis? Just a thought...
I do notice that you have a pre 94' drawing, most likely a 82' edition of the standard (14.5). Being that you do have the math data available, I would #1 make sure you have the right math, and then check the profile char. with the cad. That would be the easiest way. You could use the basics for offsets and rotations to get your data if you need to (the info is 'mostly' there).
I still am curious as to how you are stopping the rotation, as there is still 1 degree of freedom left unconstrained. It happens to be the degree you need...
Kev

[Roger Kilpatrick]

To me this drawing is really screwed up, as kbotta says there is 1 degree of freedom unconstrained, there are also basic dim's with no featur control frame (FCF), a true position callout of a counter bore within .004 to Datum -A-, (and -A- is a REFERENCE DIM), a .035 dim wall thickness from O.D. of tube to I.D. of tube with NO runout callout between I.D. and O.D., no provision for roundness of anything other than feature tolerance, and the milled "V" cuts on either side have no requirement for rotational relationship to each other. this is the reason we have someone check our prints for GD&T before they are released.

Good luck......

[Jeffrey Lovely]

Looking at this
I would (try)
after alignment to the tube ends at two directions
creating 4 lines at the mid height at the "v"
create and find center point from 2 mid points
I would make that my 0,0,0 and call it Datum -D-
This gets the length at both ends
(even though one is datum -b-)
and the profiles of the "v" - this will be the best results you
could possibly get

good luck soldier !!!

[Paul Sarrach]

All those are basic dimensions, and should not be toleranced. But if they where given to you by a Ford Engineer, Not only would they probly want them dimensionalized, but capable too.

[Jeffrey Lovely]

second look at print and cad data
i would do some caliper checks and call it a day

[d.evans]

I've had more input from engineering

They say that the C datum isn't needed.

I did end up going back up near the top of the program and rotated to a line constructed from the 2 opposing .250 Radii on one side of the part, and put that in my main alignment.

But here is more:

Using Auto edge points along the outside edge of the V cuts results in most of the profile dimensions (form and location) to be as much as .040" deviation from nom.
I kept getting weird vectors when using the CAD and edge points (seems one of the vectors was always wrong).
So I decided to use Auto Angle points instead, since along the majority of the V cuts' edge, the angle between the cut surface (small surface) and the surface of the OD of part body is NOT perpendicular. When using Auto Angle points instead of Auto Edge points, all of the previous Out-tol dimensions disappeared. But now, I'm questioning these new numbers because they are all almost perfect. This doesn't seem logical on such a flimsy part.

Do Auto Angle points work for surface profile callouts? Either way, I've gotten questionable results.

[Paul Sarrach]

Put the angle points on a known edge point program, And compare the two. I been using PCDMIS since it went to windows. And I never seen Angle points, there there, I went and looked. I have never sat down and really looked at all thingies that PCDEMONS has to offer, I only open my eyes when I need something or somebody shows me what is at the tip of my nose. I guess I spend my time more costructivly. NOT

[kbotta]

How could the [C] not be needed? What stops this part from spinning about the primary axis??? NOTHING! So, depending on how you orient the part on the cmm, you will always get different #'s, as you are not rotating from a known (or perfect) location. Can't be done. Those holes are coaxial, right ('v' holes)?
Riddle me this "what is stoping your X,Y from rotating (ir spinning)about your Z?"
KB