Questions on drawing reading

[SeasonLee]

Following are my questions when I read this drawing:

1. The drawing shows a movable gage (chuck or collet) to create datum X and datum Y (because of the diameter size Ø.250+.002-.003 is not a basic dimension), then how to check the profile tolerance between A and B (or C and D) since these portion covered by the gage.

2. Is it legal to designate two different datum (X and L or Y and M) on the same feature?

3. Is it correct to have a between symbol on position tolerance callout?

4. Is it legal for two different tolerance callouts on the same feature?
Profile line control |profile line|.006| between E and F.
Circular runout control |Circular runout|.006|L| from section A-A.

Thanks for your comments

SeasonLee

 

[KENAT]

1. Datum X & Y are in fact meant to be datum points by the look of it, not the diameters. However, I'm not sure they're properly indicated as they are only shown in the one view, it's not clear how far along those diameters they are meant to be.

2. Again, X & Y are datum points, not the entire feature. Potentially this could be legal.

3. I think this is probably legal. It's telling you the position is only required on the diameter for the length of .538 shown in the above view where X & Y are indicated (not same as X & Y datum targets). The rest of the diameter still needs to be controlled by other tolerances though.

4.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[SeasonLee]

Kenat

Please note the profile callout
|profile|.006|X|L-M|N| X is primary datum
|profile|.006|Y|L-M|N| Y is primary datum
So, X and Y here is not just a datum point.

SeasonLee

 

[SeasonLee]

Here is a clear print, sorry for the earlier post.

SeasonLee

 

[KENAT]

X1 & Y1 still appear to be indicated as datum points in the bottom left view. I see no other indications of additional datum points or other datum indicators for X & Y.

I agree the profile call outs may not be valid as normally a single datum point wouldn't form a plane for the primary datum, however this is on the limits of my GD&T comfort zone. I'm not quite sure what they're trying to achieve with the L-M. If They mean the plane through L, oriented by M then I would have thought this was the primary datum.

There appear to be several problems with the drawing, I tried to limit my initial post to answering your questions as best I could.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[ringster]

A reiew of the drawing in question, indicates to me that excessive control have been established that will result in an excessive cost for a part. Sorry but my opinion.

Any similar opinions?

 

[powerhound]

X and Y are not datum points but rather an indication of what portion of the feature must meet the tolerance. In other words the feature must meet the tolerance between points X and Y. They have nothing to do with being datum points. This should take care of questions 1 and 2. I don't know the answer to question 3 but cross hatching the area, dimensioning it, and pointing an arrow to it saying "tolerance applies in this area" is how I've handled this in the past. Regarding question 4; profile in this context must be associated with a datum so the profile of a line callout is illegal. The runout is incorrectly applied because it doesn't say where the measurement is to be taken and by definition, the feature will violate the tolerance. Showing the .180 dimension APPEARING to be at the smallest diameter is not sufficient.

Regarding similar opinions of the drawing, considering that I have no clue what the application of this part is, it would be unproductive for me to speculate on whether or not the tolerancing scheme is excessive or not, if there is such a thing, especially since that's not what the OP asked. Why would being specific in your requirements equate to an overly expensive part? What would you change about this tolerancing scheme to make it "cheaper"?

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[KENAT]

Powerhound, X & Y are used twice. In the top view to indicate a portion of the surface but also in the bottom left view they appear to be shown as Datum points.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[SeasonLee]

Powerhound

I think X and Y designated as both datum and between points, they are used repeatedly, it’s a problem need to be corrected for sure. My question is shall we use a V-block or movable chuck (or collet) to create the datum X and Y?

Based on what I understood there are no basic diameters given for the datum targets, a variable diameter gage should be used, so how can one to check ( or inspect ) the profile tolerance between point A and B (or C and D) since these portion covered by the variable diameter gage? The designer should think about the part inspection, any suggestions to solve this problem?

From what I know, it’s a shackle used on padlock, would you mind to talk more on the “cheaper” design, which feature tolerance need to be changed?

SeasonLee

 

[ringster]

It appears that a degree of tolerance relaxation would be appropriate for the .010+/-.005 and .015+/-.005 R. (Diff to verify and overly restrictive)

N is not required in the FCF for posn tol of .115 and .250 dias.

targets x and y are misapplied

Response to the OP.
2. No
3. No
4. No

 

[powerhound]

SeasonLee,

The question of a cheaper design was directed at ringster since he seemed to already know what the function of the part was.

The X1 and Y1 are either datum "points" or a datum line that is not fully defined. A V-block will not work for checking this part WRT a datum point or line.

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[vigildesign]

#3. I think it is understood that the position callout only applies to the straight portion of the shackle.

I was going to state that the diamter callout should read 2X on the left callout, then I realized that it may be easier to state the diameter of the stock material in the material callout note and take care of that requirement.

Here is an assembly drawing I found online for more info for anyone intersted:

Marcelino Vigil
GDTP T-0377
CSWP

 

[EdMcCabe]

Hi I'm Ed I am new here and rather new to GD&T but would like to try my hand at answering SeasonLee's question. I think that datum lines X and Y are established along the leftmost and rightmost edges of the part, at center, in the areas defined between points X and Y on the right and between points G and F and E and Z on the left. It looks to me as though the profile tolerances require that when measuring the notch on the left side of the u-shape, the part must be primarily positioned along datum line Y, and vice versa for the notch on the right side. I think the part may be dimensioned in this way due to distotions that would occur in the bending of the .250 wire into such a tight u-shape. Obviously, the straight lengths of the shank are the more critical design features. I also don't understand why the profile of a line callout would be wrong for the turned neck between datum points E and F.

 

[powerhound]

When specifying profile of a line, it must be related to datums. In this case, there is no datum precedence called out so it is not a legal specification.

Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[SeasonLee]

Powerhound

I think the following concepts that will apply to both profile of surface and profile of line. One unique aspect of profile controls is they can be used with datum feature reference as a related feature control, when datum features are referenced, the tolerance zone is related to DRF.

Profile controls can also be used without datum feature reference as a form control, when no datum features are referenced, the tolerance zone applies where the part surface actually exists.

For this aspect of profile control, I think |profie|.006| between E and F without datum reference is correct since it will control form here, how do you think?

But what makes me confused is the Runout tolerance |runout|.006|L| in section A-A, it will have two different tolerance callout on the same feature, which one should be applied here Profile or Runout?

SeasonLee

 

[EdMcCabe]

per 6.5.4, In most cases, profile of a surface tolerance requires reference to datums in order to provide proper orientation, location, or both, of the profile. With profile of a line tolerance, datums may be used under some circumstances but would not be used when the only requirement is the profile shape taken cross section by cross section.

 

[SeasonLee]

Profile of a line may, or may not, require datum references. But, profile of a line should not be used very often, when profile of a line is used, it is usually a refinement of another geometric tolerance, it is usually used as a refinement of surface profile. Aircraft wing is a typical example as posted by Norm Crawford.

http://www.eng-tips.com/viewthread.cfm?qid=235271

There is another excellent example of profile of line is from Tec-Ease, the line profile without datum on the first drawing should control the form here.

http://www.tec-ease.com/tips/january-06.htm

SeasonLee

 

[SeasonLee]

Hey guys, it seems we are wrong here, multi datum ( datum X and L or Y and M ) is allowable. I would rather to start a new thread to discuss it.

SeasonLee