Perpendicularity
Perpendicularity
(OP)
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
Thanks
Chuck





RE: Perpendicularity
Paul
RE: Perpendicularity
Dave D.
www.qmsi.ca
RE: Perpendicularity
Chuck
RE: Perpendicularity
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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RE: Perpendicularity
Paul
RE: Perpendicularity
Drstrole
GDTP - Senior Level
RE: Perpendicularity
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.
www.qmsi.ca
RE: Perpendicularity
While the related features shown are axes, the tolerance zone is planar. I think that's what makes the difference.
Powerhound, GDTP T-0419
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RE: Perpendicularity
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
RE: Perpendicularity
I believe that is why figs. 6-28 & 6-29 have been withdrawn from Y14.5-2009 and replaced by 6-6 & 6-8.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.
RE: Perpendicularity
RE: Perpendicularity
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.
www.qmsi.ca
RE: Perpendicularity
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.
RE: Perpendicularity
Drstrole
GDTP - Senior Level
RE: Perpendicularity
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Perpendicularity
I know some people that answered deferred to the 2009 standard but the OP specified the 94 standard.
Powerhound, GDTP T-0419
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Inventor 2010
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RE: Perpendicularity
Is drawing in question looking anything like this?
RE: Perpendicularity
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.
www.axymetrix.ca
RE: Perpendicularity
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
RE: Perpendicularity
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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RE: Perpendicularity
Yes, there is still some view dependence with Straightness tolerances. It would be nice if they got rid of this as well, and oriented the zones with a more rigorous datum-based method.
I hadn't noticed the break line in the Position FCF in Fig. 6-6, thanks for pointing that out. It probably would have been more clear if they had just included datum feature B as in Fig. 6-8.
powerhound,
I agree with you that the tolerance zones are identical - both are two parallel planes that are perpendicular to a datum axis. But I guess I'm not sure exactly what the note in 6-37 is intended to mean - "This applies only to the view on which it is specified". Would anything be different if that note were not there? I'm not sure what (if any) principle is being invoked here. It's true that the only direction of rotational control is shown in the side view, but there's nothing that is being "applied" only in the side view and not applied in the others. The fact that there is only one direction of rotational control is a consequence of the combination of considered feature geometry and datum feature geometry, not a consequence of applying any special constraints on the tolerance zone.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Perpendicularity
Thanks for the help.
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II