"INDIVIDUALLY" & "SEP REQT"

[cjccmc]

I'm using the above terms in a dimensioning scheme but not sure I am doing it correctly. We use 1994 std. Can't post a pic due to proprietary rules but will try to describe. Assume A/B/C on perpendicular faces of a rectangular part. Say I have a pattern of 4 each .250 dia holes and this pattern appears 7 times. I want a composite TP callout for these. There are also other patterns of holes on the part, all will use a composite of A/B/C first line and A only on second. None of the patterns need to be controlled relative to each other. Then is the correct callout for my .250 holes this?

4X DIA .250
7X INDIVIDUALLY
----------------------
TP DIA .030 A/B/C
DIA .005 A
----------------------
SEP REQT

What difference is there between 7X and 7X INDIVIDUALLY?

 

[powerhound]

Since all of your datums are planar and not subject to size variation, SEP REQT doesn't gain you anything. For this same reason, I don't think the individuality principle helps much either. What's wrong with just deleting the individuality and SEP REQT notes and letting the composite FCF do all the work?

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[cjccmc]

I think SEP REQT in this case means that the second line of the composite, which drives a .005 hole to hole tolerance, only applies to the four holes of one pattern, not all 28 holes of the 7 patterns. It also breaks the hole to hole tolerance of these .250 dia holes to all other holes that use an A/B/C A composite.

I'm not sure what INDIVIDUALLY means in this case. I decided to use it based on an answer I got in this forum a few months ago. Hoping to learn more about it.

 

[cjccmc]

this is the thread I was referring to above:
Link

 

[fsincox]

I would stick with SEP REQ for what you are doing.
Frank

 

[fsincox]

Technically, I don't think you need it as the lower portion of a composite is treated as a separate requirement under the newer standards, I believe.
Frank

 

[cjccmc]

I have to work to 1994 std. Like very good wine, we like to wait 20 years before using

 

[SeasonLee]

Frank
One of the many rules for specifying composite position tolerance in Y14.5M-1994 standard is: The simultaneous requirement default does not apply to the lower segment of composite position controls. Unless there are specific instructions on the drawing, the lower segment of composite position control is a separate requirement.

Season

 

[pmarc]

Maybe something like this:

4X DIA .250+/-.xxx
|TP|DIA .030|A|B|C|
|DIA .005|A|
7X INDIVIDUALLY

Some remarks to this:
1. As Powerhound stated, since all datum features are planar and not subject to size variation, SEP REQT is useless here (see para. 5.3.6.1 of Y14.5M-1994, page 92).
2. As Frank noticed, by default simulatenous requirement does not apply to lower segments of composite positional FCFs (see para. 4.5.12.1 of Y14.5M-1994, page 70). But in this case (if 7X INDIVIDUALLY was not applied) there would still be mutual spacing relationship between all 28 holes defined by the lower segment, which is not the design intent, as far as I understand. Thus 7X INDIVIDUALLY is added to untie the relationship between the 7 patterns.

 

[fsincox]

We are at 1982. They had not thought that far ahead at that point, and I would need it to be clear. It is hard to guarantee someone will say "well in the future it will mean this so, it should have meant this then, too".
ASME Y14.5M-1994 5.3.6.2 says you do not need to say it!

 

[axym]

cjccmc,

I agree with powerhound that the SEP REQT annotation does not help in this case. The ABC datum reference frame is fully constrained and the datum features are planar, so there is no datum feature shift. So specifying SEP REQT would have no appreciable effect. In addition, the lower segments of composite FCF's are separate requirements by default.

The INDIVIDUALLY annotation is used in the context of "repetitive" datum features and FCF's, in which a relationship is repeated for several sets of features (e.g. counterbores being positioned relative to their respective through holes). So that doesn't really apply in this case either.

I would stick with the composite FCF's.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[cjccmc]

Wow! I've had the wrong understanding of this for a long time. I thought SEP REQT was all about the lower FCF with the tighter tolerance, but clearly the 1994 std in 4.5.12.2 says otherwise.

Still have this question: What difference is there between 7X and 7X INDIVIDUALLY? Does INDIVIDUALLY mean anything in the example I described above?

 

[cjccmc]

I didn't see Evan's reply before my last post. So there is no difference in this example between 7X and 7X INDIVIDUALLY.
Does the placement of the 7X carry a difference in meaning? Putting it above or below the composite FCF means the same?

 

[powerhound]

cjccmc,
In my opinion, and as I alluded to in my first post, INDIVIDUALLY really means nothing here. For one, it is only directly supported in the standard as a way of relating features to repeating datum features, as stated by Evan. An example is on page 138 of the 1994 standard (Fig. 5-39). Secondly, to attempt to us it as an extension of principle would probably require a note explaining what you mean. Because of this, you may as well leave off the confusing "INDIVIDUALLY" and just let the note do the work.

I see what you're trying to do but the patterns are not related to each other anyway. They are related to the same datum reference frame and thus each pattern must be measured from the DRF.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[pmarc]

powerhound,
What about spacing between all 28 holes controlled by lower segment of the composite FCF?

 

[cjccmc]

To clarify, all patterns function independently in the part I described in my original post. I need the 4 holes of each pattern .005 hole to hole, but one pattern location to any other has no value and I do not want to drive the .005 as a hole to hole requirement for all (7 x 4 = 28) 28 holes.

My laymans interpretation would be the following:

For this callout I get exactly what I said I needed above:
4X DIA .250+/-.xxx
|TP|DIA .030|A|B|C|
|DIA .005|A|
7X


But here with the 7X above the FCF I am driving the .005 hole to hole for all 28 holes. (I would interpret this one to mean the same as replacing both the 4X and 7X with a single 28X DIA .250+/-.xxx)

4X DIA .250+/-.xxx
7X
|TP|DIA .030|A|B|C|
|DIA .005|A|

 

[powerhound]

pmarc,
Since the hole note says 4X DIA .250 and then 7X under the FCF, to me that would imply that the callout applies 7 different times. If the note were to say 28X DIA .250 then I would think they were all tied together. I'm not entirely against using INDIVIDUALLY though and the way you put it in your last post looks fine to me. It's just that sometimes extending principles causes more trouble than it's worth.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[pmarc]

Thank you, powerhound. I just wasn't sure what your preferred solution for this application was.