Perpendicularity

[ccarpent]

This may sound very basic, but I need to be sure and I can not find an example in the spec. (ASME Y14.5M 1994). When a plane surface is toleranced perpendicular to a datum that is a cylindrical feature, must it be perpendicular all around or just in the view shown? I believe all around.
Thanks
Chuck

 

[PaulJackson]

All points of the feature surface must be contained between two parallel planes, perfectly perpendicular to the datum feature (the axis in your case) spaced "the specification" apart.

Paul

 

[dingy2]

Answer is short - all around and not just the view.

Dave D.

http://www.qmsi.ca

 

[ccarpent]

Thank you.
Chuck

 

[powerhound]

Dave, Paul,

Fig. 6-37 gives an example of a planar tolerance zone related to a cylindrical datum and it specifically says that it only applies to the view on which it is specified. Is this figure not a good example of what the OP is asking?

Powerhound, GDTP T-0419
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[PaulJackson]

That example is an axis to an axis... if I understood Chuck's question his control is a plane to an axis.

Paul

 

[drstrole]

In Figure 6-37, the tolerance value is not preceeded by a diameter symbol, making it in the view shown. If it had a diameter symbol it would be contolling the direction in and out of the page (for lack of better verbiage). Depending on which control is needed would be what specified.

Drstrole
GDTP - Senior Level

 

[dingy2]

Powerhound:

6-37 in the 94 version is an axis (hole) to a axis (OD) as Paul has stated (see Paul, we can agree on some things).


Dave D.

http://www.qmsi.ca

 

[powerhound]

Dave,

While the related features shown are axes, the tolerance zone is planar. I think that's what makes the difference.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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[Belanger]

Drstole wrote that a dia symbol in Fig 6-37 would then control the axis in and out of the picture. But another datum reference would be required to really achieve that.

I mention this because in that same 1994 standard there are two angularity examples (Fig 6-28 and 29) that seem to me to have identical meaning. What is the purpose of having the dia symbol in Fig 6-29? The hole can tilt in and out of the page and the hole's axis might still be 60º from the floor. And it doesn't help control straightness, since it's controlling the axis of the AME. The only thing I can think of is if an MMC modifier were included, then the dia symbol would be conducive to a functional gage. But we're talking RFS here.

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

 

[pmarc]

J-P,

I believe that is why figs. 6-28 & 6-29 have been withdrawn from Y14.5-2009 and replaced by 6-6 & 6-8.

However I have to admit that presence of diameter symbol on 6-6 is still quite strange, especially that in paragraph 6.4.2(b) it is clearly said that the tolerance zone was two parallel planes and not a diameter.

 

[pmarc]

I should write 'cylinder' instead of 'diameter' in the last word of the last sentence of my last post.

 

[dingy2]

pmarc:

Fig. 6.6 in 2009 is a diametrical tolerance zone and it is covered by 6.4.2 (c). Looks like the angle is 60 degrees and 90 degrees (other axis).

Dave D.

http://www.qmsi.ca

 

[pmarc]

Dave,

Fig. 6-6 is mentioned in paragraph 6.4.2(b) in which the description of a tolerance zone defined by two parallel planes is described. Angularity tolerance (bottom FCF) is referring to a single datum A only, so as J-P stated there is no control of axis tilting in and out of the page, and therefore the diameter symbol does not make much sense.

 

[drstrole]

Appologies for my posting, I should have thought about what I was thinking and writing more clearly before I hit the submit button. Had I done that I wouldn't have posted.

Drstrole
GDTP - Senior Level

 

[Belanger]

No, no problem ... the angularity example that I mentioned had always sat strangely with me, so I was more attuned to why a secondary datum is needed.

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

 

[powerhound]

So what's the consensus folks? I still believe that the answer to the OP is that the tolerance applies only in the view shown as evidenced in my two previous posts, but there are some great minds here who have corrected my errant ways in the past

I know some people that answered deferred to the 2009 standard but the OP specified the 94 standard.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
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[CheckerHater]

So many posts and no pretty pictures.

Is drawing in question looking anything like this?

 

[axym]

Hi All,

To address the OP, I would say that the parallel-plane zone must be perpendicular to the datum axis "all around" and not just in the view shown. I guess that my tendency to agree with Paul outweighs my tendency to disagree with Dave ;^). None of the examples in '94 or '09 deal with this specific case, and the "applies only to the view on which it is specified" stuff seems to only be applied to cylindrical considered features.

The side conversations have brought out some interesting issues. I think that there were several questionable things in Y14.5's orientation tolerance examples, and most (but not all) were fixed in '09.

The two examples in '94 (Fig. 6-28 and Fig. 6-37) in which the orientation control "applies only to the view on which it is specified" were deleted in '09. Hooray! The "view" cannot be rigorously defined on a real part. These two examples also had a parallel-plane zone for a cylindrical feature which doesn't make sense to me (see below).

Let's look at Fig. 6-31 in '94 (Fig. 6-7 in '09). The Parallelism tolerance zone is specified as two parallel planes, but I think that this is a flawed concept. It's true that the axis can lie anywhere in a volume between two parallel planes 0.12 apart. But to me it's a cylindrical zone that can freely translate and can also rotate in the direction "parallel" to the datum plane. I know that this is subtle distinction, but I have no problem spitting hairs ;^). To be consistent, the tolerance zone in Fig. 6-31 should be specified as cylindrical as it is in Fig. 6-32.

The Angularity examples were improved in '09 with the addition of location controls. But I still have one problem with Fig. 6-6. The Angularity tolerance is supposed to be a refinement of the location tolerance, but because only one datum feature is referenced the Position tolerance is only controlling orientation anyway. So we have an orientation tolerance RFS refining a Position tolerance at MMC that is only controlling orientation. Some would say that the Position tolerance in 6-6 is illegal, because it doesn't locate the feature ;^). But we beat that one to death a few days ago.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Belanger]

Two minor points, Evan. I agree with your first paragraph, with the modification if that last sentence to say that that concept is for cylindrical zones as well as those that have no depth, such as straightness over a flat surface (Fig. 5-6).

I too am glad that they ditched the notation about applying "only in the view shown." Perhaps they did that because they wanted to get away from the orthographic stuff and realize that there is also 3D math modeling, where talking about a specific view would be confusing.

The other point is the last thing you stated ... notice that the FCF for the position tolerance has a break line, implying that there will be other datum references. (Of course I maintain that it would be illegal to stop with just A, but everyone can refer to the other thread for that can of worms.)

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