Translate into GD and T language: How? Which is the best way? 1

[greenimi]

Design intent: to control Ø.160/.156 hole location relative to the 1-1/16 hex.
What we don’t want end up having is a part with the hole positioned near the corners of the hex-see sketch-
No control to center hole or to Ø1.11/1.09 hole is needed.

I have 3 options to “translate” in GD and T language the above design intent.

Which one do you think is the one (if any) we should/can use? Are there any differences between these 3 options or they are producing similar results and have identical meanings.

Option #2 is to made to be able to have a functional gage built to verify the requirement. Can we achieve the design intent by using a functional gage? I understood Boundary note is optional.


What else do you think is missing from this drawing to get the design intent? In other words, how the part could look like if we have these options depicted on the drawing?

Do you think can be a better way—less complicated in GD&T language—to get the right parts?

Thank you

 

[fsincox]

Two initial thoughts,
When you say no control to OD is needed, you do want the flats on the part don't you?
In my opinion you are abusing "all around" if you do not actually define the profile all around.
Frank

 

[fsincox]

What standard are you working to? Do you want the center hole on the part?
Frank

 

[greenimi]

Frank,
We are using ASME Y14.5-1994. The center hole is there, but you easy "pretend" is not there. Just ignore it so to say

And yes, I do want the flats (hex) on the part to be there.

If I remove "all around" circle is it better, means less confusing?

Thank you again

 

[pmarc]

greenimi,
First of all, none of the options controls hole to the hex, they all control hex to the hole.

- For option #1, I do not think you may have the same datum references repeated in the lower segment of profile composite FCF. It gives you nothing.
- In order to make option #2 legal, you need to have basic dimension for diameter 1.09-1.11 and for hex.
- Option #3: Bigger tolerance value cannot be specified in lower segment of feature control frame.

 

[greenimi]

Pmarc,
Let me rephrase it: we would like to control the relative position between the hole and the hex.

Option #1: by having the lower segment the intent was to control the rotation of the hex to the datum reference frame. If this was achieved or not, that could be true, but that was the intention.

Option #2: if I have basic on Ø1.11/1.09 do I need to have it also --this diameter- as a datum and reference it on the DRF? I have 3x 1.063-already basic-- to control the hex. Maybe just to remove 1-1/16 hex note would be okay?

Option #3. Here I am confused. Why the size and form, could not be bigger than the location+orientation? Or Am I missing something? Profile .010 with no datum will control size and form.
profile .005 with A and B at MMB control location and orientation.
Am I right?

Thank you

 

[CheckerHater]

Crazy suggestion:
Drop the datum,
Control everything in relation to [A],
Let “simultaneous requirement” do the job.

 

[fsincox]

Actually I am interested to see if others are of the same opinion of my "all around" comment.

If you want the flats to be there on the OD, then, you do care somewhat and you must decide how much you need to be there and that will help you determine the tolerance.

What he is saying is you can't do it with profile as shown in option 3. Option 2 does what you want for the flats holding them tighter in location than the basic form. Basically, like the ISO coaxial.
Frank

 

[CheckerHater]

Sorry, brocken link.

 

[SeasonLee]

Frank

The all around symbol can be used on hex (polygon) surface, the all around symbol extends the profile tolerance zone to apply to all sides of the hex (polygon), one application example is on the hex head cap screws.

SeasonLee

 

[SeasonLee]

Forgot to add : Of course, the profile of the hex need to be clearly defined.

SeasonLee

 

[greenimi]

SeasonLee,

How I have it now, the profile of the hex is not clearly defined? Just asking.
If no, what am I missing?
Thank you

 

[fsincox]

Season,
The question is basically: can "all around" actually be used intermittently as is being done here? I feel it is a fundamental conflict of terminology; this is more a “6X” condition, IMHO.

Frank

 

[SeasonLee]

At least the diameter 1.09~1.11 should be basic dimension, here is an example.

SeasonLee

 

[pmarc]

greenimi,
1. Regardless of your 3 options, if your concern was only to control profile of 6 flat portions of the hex and not whole outline of the part including cylindrical portions, then I would say your all around profile specification is illegal. It cannot be applied to the outline which is interrupted by anything. So either you remove all around symbol and add '6X' to profile callout or define diameter 1.09-1.11 as basic 1.10 and leave all around symbol as it is. (Is this what you asked for, Frank?)
2. As for your question about my comment on option #3, it is really geometrically impossible to have lower segment tolerance value bigger than for upper segment and gain something. Refer to para. 6.5.9.1 of Y14.5M-1994 clearly specifying that: "Lower segment[...] specifies smaller profile tolerance for the feature within the profile locating zone (form and orientation refinement)".
3. I am just wondering if switch on diameter dimension 1.09-1.11 to basic 1.10 will be enough to fully define true profile of the outline. I always try to visualize similar situations by imagining what will happen if I tried to draw this outline (with all dimension given and implied) in the sketcher of a CAD software. Would the sketch be fully constrained then? I do not have access to my CAD program right now, so cannot tell with 100% certainity, but I am afraid in this case it would not, since there is nothing on the print saying what are the basic lengths for flat or arc portions of the outline. As far as I see there is no tangency at points where flats and arcs meet, am I correct?

CH,
Your idea is not so crazy. The scheme you proposed basing on "simultaneous reuirements" concept makes sense, at least to me. For sure it is elegant and looks simplified to maximum on the print. For your sketch and in general, I am just thinking, how many inspectors will verify position and profile all around in one step, meaning in a way they should be verified? I would just be afraid that the concept leaves too much space for not grasping mutual locational relationship between the hole and the hex during measurements done by some not enough educated inspectors.

 

[fsincox]

pmarc,
Yes, Thank you.
I also agree with your other comments. My problem with the simultaneous requirement is really simply only that "they" (manufacturing and inspection) generally object when I play the game that way. If the rules can't be used in practice what good are they to me?
Frank

 

[pmarc]

greenimi,
I checked in my CAD program what I had mentioned in point 3 of my last post. Please have a look to attached pdf. You will see what my point was.

http://files.engineering.com/getfil...36fc2&file=True_profile_spec_completeness.pdf

Hope this helps.

 

[CheckerHater]

I would just be afraid that the concept leaves too much space for not grasping mutual locational relationship between the hole and the hex during measurements done by some not enough educated inspectors...

"they" (manufacturing and inspection) generally object when I play the game that way...

I understand the concern, but aren’t we approaching slippery slope there when trying to cater to the lowest common denominator?
We had a discussion in our company, if documents should be sufficient for the complete stranger to do the job (and our shop is spoiled rotten). I quoted old standard from the times when standards actually said something rather than referencing each other:
“Engineering drawings… shall provide engineering definition sufficiently complete to enable competent manufacturer to produce and maintain quality control of item(s)…”
The key is “competent manufacturer”, not the “bum from the street”. We finally agreed that manufacturer has to carry some part of the weight.
Several manufacturers don’t understand Rule 1 to begin with.

 

[fsincox]

CH,
I understand, I am only trying to show that I am not opposed to it in concept, I am attempting to convince pmarc and others I am not really such a bad guy. In practice it seems to fall short, IMHO, I suspect the ISO made the other choice for that reason.
My interest, in this area, has always been in communization and harmonization of both of the standards to make it easier on us all, preparing for the lowest common denominator, or worst case, is standard practice for most other areas of engineering training. Therefore, I see it as only being consistent with the general engineering philosophy. Again, I suspect the ISO does too.
Frank

 

[pmarc]

Frank,
Never said nor even thought you were a bad guy
I really appreciate all the efforts you put into ISO vs. ASME battlefield in this forum.