Composite Frame for Single hole 4

[Madhu454]

Hello,

Please see the attached drawing.
Figure-1 : A composite Position frame is applied for the hole.
Figure-2 : The same hole uses Position control and a perpendicularity control.

Question : 1) Can Composite position frame be applied to single hole.?
2) I have a doubt that,composition position frame is used only when there is a pattern of holes, as ASME says the upper frame 'PLTZF' and lower frame is 'FRTZF'.
3) Is figure-1 is legal specification? or do I need to dimesion the part as shown in Figure-2. or both is Fine?

Plz suggest.


Madhusudhan Veerappa
Mechanical Engineer

 

[ShaggyPE]

I am not an authority, but here is my take.

Figure 1 in not appropriate as a composite for the reason you mentioned. If you make it a two line position tolerance you can achieve what you desire (same as what you have except two position symbols).

Figure 2 is perfectly acceptable.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[fsincox]

I have always been told no to a composite pattern on a single feature, which do not think is specifically stated anywhere in the actual standard.
BUT:
1) KISS principle, if all you want is orientation say it.
2) Composide position tolerancing is laid out under section 5.4 Pattern control (1994 version), using the pattern relation definitions: FRTZF & PLTZF.
Frank

 

[dingy2]

You cannot have a composite feature control frame on a single hole. The bottom section or FRTZF is utilized inside a pattern of holes and perpendicular to datum A.

The second example is correct where there is a positional requirement and then a perpendicular one which is a refinement of the position. The feature control frame outline for both top and bottom sections should line up on the left side.

Dave D.

http://www.qmsi.ca

 

[pmarc]

Agree with Dave. Composite FCF should not be applied to a single feature of size. Paragraph 7.5.1 of Y14.5-2009 states that: "Composite positional tolerancing provides an application of positional tolerancing for the location of feature of size patterns as well as interrelation (constrained in rotation and translation) of features of size within these patterns".

Second figure is correct.

 

[Belanger]

Dave and the others are correct. The position symbol cannot be used if the only quality being controlled is orientation (perpendicularity). It's a common mistake -- there's even a Tec-Ease tip that promotes such a practice!
But paragraph 7.2 of the Y14.5 standard states that position is "the location of one or more features of size..." And by definition, "location" means that there is a distance involved. So if perpendicularity is all that is being controlled, then you don't want to use a symbol whose function is to control a distance.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[ewh]

...by definition, "location" means that there is a distance involved

I don't think it is quite that simple... the definition of "location" also includes position, and while you may not want to use the symbol for orientation only, it does control orientation.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[Belanger]

I agree that orientation is automatically covered when a location tolerance is given, but the original question was the opposite: using a location symbol when the ONLY quality desired is orientation. That's very different. Anytime we use the position symbol, that means there must be a distance involved.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

J-P, I do not think that OP's intent is to control orientation only. He wants to control position too. The question is whether composite position FCF is equally legal to 2 separate FCF's (position and orientation) or not and which is correct?

 

[Belanger]

Yes, pmarc -- thanks. I guess I was focusing on the bottom part of the composite, though, to explain why it doesn't fall under the banner of the position symbol. (I guess I can't really call it a FRTZF?). But like you, I would go with the second option that he presents.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[axym]

I would say that Figure 2 is correct and preferable because of its simplicity and directness. The Perpendicularity tool exists, so let's use it.

I would also say that Figure 1 would apply exactly the same controls as Figure 2. There is absolutely no difference that I can see.

Whether Figure 1 is legal or not is an interesting question. I would agree that applying composite Position to a single hole is a very poor practice, but I'm not sure that it violates any rules. JP, the "location requires a distance" argument doesn't hold enough water for me. There are plenty of statements in Y14.5 that are correct in a general sense but also have exceptions. For example, the passage you quoted mentions features of size. But Position can also be applied to irregular features that are not features of size, when the Boundary tool is used. Further, the PLTZF and FRTZF acronyms don't hold up to scrutiny either. The PLTZF doesn't really locate the pattern, it locates the features. The FRTZF usually does more than just relate the features - it can orient the features and can locate them as well. It all depends on the specific configuration of considered features and datum features.


Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Belanger]

I hate to sound like I'm splitting hairs, but it seems pretty clear to me. Think of it this way:

Position controls location and orientation.
Perpendicularity controls orientation only.

similarly:

Parallelism (surface) controls orientation and form.
Flatness controls form only.

When you guys say (or imply) that it might be OK to use the position symbol just for its orientation effect, it's akin to saying that it's OK to use parallelism if I just want flatness control. I would say no: parallelism has orientation as its unavoidable duty, and the flatness effect is a free by-product. Same here: position's intrinsic purpose is to control location, and orientation is a by-product. So I'm just saying that logically you can't use a symbol for its fringe benefit and totally ignore its main purpose.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[dingy2]

J-P:

I totally agree with you on this one. Positional tolerances on a single hole to datum A doesn't make sense. If one was trying to reflect a perpendicularity, use it.

FRTZF does not exist in the first example. We do not have features inside a pattern since we don't have a pattern so, thus, I do not agree with Evan. The only relationship the single hole has with datum A is perpendicularity. That's it.

Dave D.

http://www.qmsi.ca

 

[pmarc]

Whether Figure 1 is legal or not is an interesting question. I would agree that applying composite Position to a single hole is a very poor practice, but I'm not sure that it violates any rules.

Evan, isn't the meaning of paragraph 7.5.1 of Y14.5-2009 enough to say that applying composite positional tolerancing to a single feature violates the rule?

 

[Madhu454]

Hello JP,

I understood your point that we should use orientation control when I am interested to control the perpendicularity, rather than using position to control the same. I understood that it is a poor practice to use the composite position frame for single hole.

As PMARC mentioned in above string,

1) As per ASME, using composite position frame to a single hole is legal or not? Is it documented any where?

I dont have a copy of 2009 standard to refer the session 7.5.1 mentioned in the above string and i have seen drawings where they use composite position frame to control single hole? I have confusion whether is legal or not.

Madhusudhan Veerappa
Mechanical Engineer

 

[pmarc]

Madhusudhan,
If you have Y14.5M-1994 take a look to paragraph 5.4.1. Meaning of its first sentence is very close to the statement from 7.5.1 of 2009 edition which I cited a few posts above:

[1994] "Composite Positional Tolerancing. This provides a composite application of positional tolerancing for the location of feature patterns as well as interrelation (position and orientation) of features within these patterns".

 

[ewh]

I agree that the second example is preferable... I just took exception to the statement that location requires distance, and the inference that true position only controls distance.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[Belanger]

I give up.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[dingy2]

ewh - positional (not true position) does not only control location but orientation.

Dave D.

http://www.qmsi.ca

 

[ewh]

Awe... where's the fun in that, JP? ;-)
I was just venting about a pet peeve of mine, which is the use of absolutes, or terms in an absolute sense.
I have no argument against your explanation otherwise; it is a good one and I appreciate the knowledge you have shared with us. Heaven knows I can use all of the help I can get. I guess I don't need to pick all of those nits I find.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]