Does Profile Locate?

[randy64]

See attached example. This is the engineer's markup. Engineer says that the 2.000 basic dimension locates the slot (similar to positional tolerance). I say no - the 2.000 dim should be replaced with a 1.6875 dimension to the edge of the slot.

I suspect it may be the same in the vertical location of the slot. Also, I'm not sure about the basic FULL R dimensions.

What say you?

Thanks!

 

[ewh]

The engineer is (more) correct at locating the slot center line.
This is in line with locating the radii centers vertically.
Either method is correct and will define the slot location, but locating the center lines is more common in my experience.
The FULL R callout should not be basic as it is more of an indicator note than a dimension; the basic width dimension determines the radius.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[chez311]

Engineer says that the 2.000 basic dimension locates the slot (similar to positional tolerance). I say no - the 2.000 dim should be replaced with a 1.6875 dimension to the edge of the slot.

Your engineer is correct, the 2.000 dimension locates the slot just fine. Since your width is basic, it could be done either way with the same result. Same is true for the vertical dimensions.

To the question contained in your subject line, yes profile can control location, orientation, size, and form depending on the configuration and referenced datum features. In your case all four are controlled.

In regards to the "full R" its definitely questionable - I've seen it in conjunction with directly (+/-) toleranced radii (and even then is not totally unambiguous what is meant, but I understand the intent) but with a feature fully defined with basic dimensions as you have I would consider it extraneous.

 

[greenimi]

Well, I would say that the basic dimension does not locate or orient a feature!
Basic dimension locates and / or orients the tolerance zones AND the tolerance zone(s) limit the imperfection of the features!
Should be a very clear distinction.

 

[Burunduk]

I will assume that the drawing is according to ASME Y14.5-2009.
Profile does locate when it references datum features, but not the same way as position.
While position would control the center plane of the slot, a profile control creates a tolerance zone for the surface.
An all-around symbol should be added to the leader from the feature control frame, otherwise the default condition applies in which just the radius is controlled (because the arrow points to the radius).
As for the radii specification for a slot, the standard says:

"For fully rounded ends, the radii are indicated but not dimensioned. For features with partially rounded ends, the radii are dimensioned"

In this case, there are fully rounded ends. "Indicated" means "2X R" (basic). So "FULL" is not really necessary.

 

[chez311]

greenimi,

You are correct, I should have made that distinction.

Basic dimension establishes your true profile (theoretically exact location/orientation relative to DRF as well as size/form)

Profile tolerance establishes your tolerance zone relative to your true profile and allowed variation of the feature from the true profile.

 

[randy64]

To those who say the slot is located via the centerline using profile, can you please explain how that works? I mean, profile applies to the shape of the slot, and, yes, a dimension to an actual physical feature of a slot can also locate it. I just don't see how the .625 dimension can be located using profile. If we were using positional tolerance, I would buy it.

 

[randy64]

Oh, also, yes we are using 2009, and I forgot to put the all-around symbol on the profile callout.

 

[randy64]

I would also buy in if there were a basic .3125 dim from the centerline to one of the sides of the slot.

 

[Burunduk]

As pointed out by chez311, since the dimensions are basic, it doesn't matter if you specify the edge distance directly, or consider the combination of distance to center and width. There is no tolerance accumulation with basic dimensions. It is perfectly understood that the left side of the slot is limited in a portion of a tolerance zone equally distributed around a portion of the true profile located at 2.000-.625/2 = 1.6875 from datum B.

 

[randy64]

Burunduk, you say "It is perfectly understood that the left side of the slot is limited in a portion of a tolerance zone equally distributed around a portion of the true profile located at 2.000-.625/2 = 1.6875 from datum B."

To me, this isn't about accumulating tolerances, it's about using profile to locate something that is not part of a profile (a centerline).

You say "It is perfectly understood..." No, it's not. I see that as an assumption you are making. I see no examples like that in the standard. In your formula, the /2 is an assumption I don't believe can be made with profile.

If someone can show me something in the standard that backs this assumption up, please do so.

 

[Burunduk]

Refer to paragraph 1.4 FUNDAMENTAL RULES, (k)

 

[chez311]

randy,

It is implied the width dimension is equally disposed around the center plane located 2.000 basic just as it would be if the width were directly toleranced. There is no need to have an explicit .3125 dimension to one of the sides. It can be added in this case, but is not necessary.

For an example in the standard, see the below fig 4-33 the basic 30 dimension is implied equally disposed about the center plane as is the basic 17 establishing location of the holes. There is neither a need for a 15 (for the width) or 8.5 (for the holes) dimension.

 

[randy64]

Chez311, I would argue that the 30 basic is not equally disposed about the centerline - it is establishing the centerline since it is datum B. Since the 17 basic is held to datum B (via pos tol), it is assumed to be centered about that datum. Again, that dynamic is true in positional tolering, but not profile, IMO.

Burunduk, 1.4 FUNDEMENTAL RULES (k) speaks to axes, center planes, or surfaces that are shown coincident. This is not that case. You are trying to say that a feature is assumed to be equally disposed about a centerline if it is controlled via profile. 1.4(k) does not address that situation.

 

[greenimi]

the 30 basic is not equally disposed about the centerline - it is establishing the centerline since it is datum B

Why are you talking about centerline when I think center plane is shown in chez311's picture?

 

[greenimi]

I say no - the 2.000 dim should be replaced with a 1.6875 dimension to the edge of the slot

Are you locating a hole from its edge? Then why the slot should be different? A slot is just an elongated hole...….

 

[Burunduk]

randy64,
Ok, forget 1.4 (k).
The only conclusion you have to make is the vertical centerline shown on the drawing represents the center plane of the true profile of the parallel faces of the slot. This true profile is used to establish the tolerance zone that locates the feature. If you claim that the above conclusion can't be made - I don't know how else I can be helpful.

 

[greenimi]

You are trying to say that a feature is assumed to be equally disposed about a centerline if it is controlled via profile. 1.4(k) does not address that situation

(k) A zero basic dimension applies where axes, center
planes, or surfaces are shown coincident on a drawing,
and geometric tolerances establish the relationship
among the features. See para. 2.1.1.4.


Where do you see the word "centerline" in 1.4(k)?

 

[randy64]

Greenimi does not a centerline on a drawing represent a center plane? I don't think I've ever seen a center "plane" depicted on a drawing. What does that look like?

Anyway, it's besides the point in relation to the situation at hand. This isn't about things that are coincident, it's about assuming something is centered, or equally disposed - which I don't see when discussing profile.

 

[randy64]

Greenimi, I do not locate a hole from its edge, I locate it from its center, because that's how things are located using positional tolerancing. If you're using profile, then you use the edge or surface. That's my whole point. I believe people are conflating pos tol principles with profile principles.