Perpendicularity on multiple holes along single axis

[Raddy13]

I'm working on a machining drawing and one of the features is a hole with multiple diameters (from 15, 18, 20, and 22mm) all along the same axis. Do I have to set a perpendicularity control frame for each dimension or can I set it for the top most dimension and have it apply to entire axis for all the holes?

 

[chez311]

Raddy13,

What standard are you using? Is it ASME Y14.5-2009 ?

Perpendicularity controls the axis derived from the feature, not the other way around. Each diameter would be considered a different feature, there would be no implication that a FCF applied to one would apply to any of the others without a note stating as much (something like DIAMETERS INDICATED Y or nX COAXIAL DIAMETERS or similar attached to the FCF). If they were interrupted/separate diameters of the same size this could be accomplished through the pattern creation mechanism with simply "nX" number of instances notation.

Note that perpendicularity controls orientation ONLY - the 4X diameters would not be required to be coaxial to each other without an additional position control.

 

[greenimi]

Features shown perpendicular, coaxial, or symmetrical to each other must be toleranced for location or orientation to avoid incomplete drawing requirements. --excerpt from ASME Y14.5-2009 paragraph "2.7.4 Relationship Between Individual Features"

Now the question become: Can you show only one single perpendicularity callout with multiple leader lines?

 

[Raddy13]

Thank you for the replies. I just went ahead and added frames to each dimension. Appreciate the help!

 

[greenimi]

Looks like 9-6 / 2009 open the door to use only one FCF with multiple leader lines. Am I wrong in saying that this approach could be applied to the perpendicularity too?

 

[pmarc]

greenimi,
In fig. 9-6 all leaders point to the surfaces of the features. Based on my understanding of OP's case, she/he wants to apply multiple perpendicularity FCFs to the features of size. With the multi-leader approach this would require the leaders to terminate at the diameter dimensions, which is not something that fig. 9-6 shows.

Raddy13,
Do the 4 holes have any location control applied? As noted by chez311, perpendicularity tolerances control orientation only, so in absence of a location tolerance for the holes they are not required to be coaxial to each other within any finite limit.

 

[greenimi]

Thank you pmarc,

Since I came here often to LEARN (and I think the main OP question has been answered) may I extend a little bit my own question for you (about the multi-leader approach):

With the multi-leader approach this would require the leaders to terminate at the diameter dimensions, which is not something that fig. 9-6 shows

If, for example/ hypothetical case , in fig 3-29 / 2009 another leader line is extended from the current / existing perpendicularity callout (datum feature C) to the size callout of Ø35.5-36.0 (outside diameter) AND/OR another leader line is extended from the same perpendicularity (perp. Ø0.08MMC to A primary) to the inside diameter size dimension of Ø20.00-20.13, would you think these additions (again, my "purposely made case") is valid in ASME?

Observation# 1: Naturally, circular runout of 0.06 to A|C| might needed to be removed or at least not to be associated with the size dimension to not create a potential conflict. There are people that are not happy by association between size dimension and runout, but I WOULD LIKE to keep that apart from my adjusted "multi-leader" question ( a separate side discussion could be developed)
Observation #2: Datum feature C, might needed to be removed from the current/ existing perpendicularity Ø0.08 MMC|A|

What do you think? Are there any Y14.5 rules that I am violating by using the multi-leader line approach on the perpendicularity as described above?

Observation #3: I agree that the location control - coaxiality - of the OP's holes is/are needed, and perpendicularity (with multi-leader or separate FCF's) are refinements.

In the same token, in ISO GPS, "A" Ⓐ circled modifier (modifier not available in ASME) could be used for the derived feature (as relatively recently discussed on a different forum) so, my question is:
Could only one perpendicularity FCF callout with multiple leader lines and "A" Ⓐ circled modifier be used legally in ISO for this task ( to unclutter the drawing)?

Thank you pmarc for contribution in my continuous education in GD&T.

 

[chez311]

pmarc,
Good catch on the difference between the leader lines terminating on the surface vs. diameter dimensions. Setting aside its use on an orientation control, would you say the interpretation strictly per Y14.5 of using multiple leaders is simply a "number of instances" notation? What I mean by that is that the result would be the same if you applied separate orientation tolerances and does not impart any special meaning/requirements (mutual location/orientation outside of what is specified in the actual FCF themselves). Y14.5-2009 fig 9-6 and associated section 9.6 seems to suggest this as it says "Surfaces may be specified individually or in groups without affecting the runout tolerance". Taking this a step further, in fig 4-22 if one were to remove the "2X" but keep the multiple leader lines would you say there is no requirement for mutual location of the surfaces? The use of multiple leaders does not fall under Y14.5's definition of a pattern and since the FCF is datumless SIM REQ is not applicable (at least as far as I understand - I know there may be some debate on this topic).

greenimi,
No matter what grouping method of notation is used, the result should be the same as if one put individual orientation tolerances on each diameter. I misspoke in my initial post, use of "nX" or other similar grouping notation combined with an orientation control does NOT fall under the standard's pattern creation mechanism. Per Y14.5-2009 1.3.42 a pattern is "two or more features or features of size to which a locational geometric tolerance is applied". Since we are talking about an orientation tolerance, any application of the notes I suggested would be understood only as a "number of instances". This was actually the way I meant it, I just misused the term "pattern" in the context of Y14.5

 

[pmarc]

greenimi,
Technically, what you call the "leader line" for the perpendicularity tolerance in fig. 3-29 is not a leader line. It is the extension line of the dimension line (see para. 3.5(d)). Regardless, I think I can imagine someone trying to create extension lines of the other diameter dimension lines and attaching them to the perpendicularity FCF, even though this still wouldn't look exactly the same as in fig. 9-6 (arrowheads would be missing).

Observation #1: I see what you are saying and I agree that it is a subject for a separate discussion. For what it is worth, I personally understand why there are people that say that runout FCF should not be associated with a size dimension. But I also know there are individuals that think this is not a problem at all.

Observation #2: I agree that datum feature symbol could not stay where it is now if the approach proposed by you was used.

Observation #3: I am glad we agree on this.

Regarding the usage of (A) modifier in ISO, yes a single perpendicularity callout with this modifier and multiple leader lines terminating at the surfaces could be used. Not sure, however, if this (having multiple leader lines on the drawing) would really always help to unclutter the drawing ;-)

-------

chez311,
If we go strictly per Y14.5, I would say that for orientation tolerances both approaches, i.e.: (1) application of N separate tolerances & (2) application of a single tolerance with N leaders, result in the same requirements. I am not so sure the standard should exclude orientation tolerances from the simultaneous requirements rule, but that's a slighlty different topic.

As for fig. 4-22, I would say that removal of "2X" would cancel the requirement for mutual location of the surfaces because the pattern creation mechanism would no longer exist. Just like there should be "2X" added to the profile tolerance in fig. 8-16 to be able to say that both tolerance zones have to be basic 10 apart (i.e. that they form a pattern). This particular error has been actually fixed in 2018 version (fig. 11-18). 

 

[greenimi]

Technically, what you call the "leader line" for the perpendicularity tolerance in fig. 3-29 is not a leader line. It is the extension line of the dimension line (see para. 3.5(d)).

I am sorry for my dyslexia. And thank you again for the proper correction.

For what it is worth, I personally understand why there are people that say that runout FCF should not be associated with a size dimension. But I also know there are individuals that think this is not a problem at all.

Looks like some folks won the battle because in fig 6-30 (2018) size and runout are “divorced” (unlike its equivalent 3-29 from 2009 within which size and runout are still “married”)
At the cursory level, I couldn’t find the proper verbiage (in 2018) for this separation, but I am sure I haven’t looked hard enough. The appropriate text might be there (I hope) in 2018 standard.
If you know it from the top of your head, please let me know where should I look for this written/ text requirement or explanation.

I am not so sure the standard should exclude orientation tolerances from the simultaneous requirements rule, but that's a slighlty different topic.

.....or maybe at least runout to be included (if not all the orientation tolerances).(--Just me adding to your statement--)
I've seen (on different forums and discussions) experts complaining more about the runout than the orientations….But you might have your reasons, because knowledge is out of the question

Speaking about runout: Never seen any ISO examples (ISO 1101, ISO 5458) where runout is used with SIM. (and yes, I’ve seen orientation tolerances - parallelism mostly - used with CZ).

Pamrc,
My last question for this week:

For example if fig 9-6 / 2009 was per ISO GPS, then would be a difference between:
- total runout with CZ inside the FCF’s and multi-leader line approach (only one FCF)
And
- 4 (four) separate runout FCF’s with SIM’s under each of them ?

(I am only talking about the total runout shown with multiple leader lines –there is only one--shown in the rightmost upper corner of the picture)

Thank you and have a great weekend.

 

[pmarc]

Looks like some folks won the battle because in fig 6-30 (2018) size and runout are “divorced” (unlike its equivalent 3-29 from 2009 within which size and runout are still “married”)
At the cursory level, I couldn’t find the proper verbiage (in 2018) for this separation, but I am sure I haven’t looked hard enough. The appropriate text might be there (I hope) in 2018 standard.
If you know it from the top of your head, please let me know where should I look for this written/ text requirement or explanation.

As far as I see, there is no statement in the runout section of Y14.5-2018 that would clearly prohibit association of a runout FCF shall with the diameter dimension. Most of the figures in that section seem to suggest this but there is still at least one that doesn't (fig. 12-12).

This rule has been given in paras. 8.4.3 and 8.4.4 for circularity and cylindricity, though. But again, the standard for some reason (probably a mistake) makes an exception in fig. 8-13.

I've seen (on different forums and discussions) experts complaining more about the runout than the orientations...

I've seen that too. And I indeed heard people complaining about not having orientation tolerances included in the simultaneous requirement rule. In the latter case this would just be orientational, not locational, simultaneity.

For example if fig 9-6 / 2009 was per ISO GPS, then would be a difference between:
- total runout with CZ inside the FCF’s and multi-leader line approach (only one FCF)
And
- 4 (four) separate runout FCF’s with SIM’s under each of them ?

The question isn't easy to answer in case of runout tolerances in ISO. For example, in the CZ approach the two runout tolerance zones for the cylindrical surfaces would have to shrink or grow as if they were a single (combined) tolerance zone. In the SIM approach, I am not sure the same requirement would be imposed.

 

[chez311]

pmarc,

Interesting note about Y14.5-2009 fig 8-16 and the correction in 2018 (11-18), I would agree the lack of "2X" in 8-16 is an error and the change in 2018 solidifies that.

Thanks for your clarification. I agree that the exclusion of orientation tolerances from SIM REQ always seemed discontinuous to me. I always intuitively felt that there was no real good reason why there couldn't be simultaneous requirements for orientation (ie: no rotation between DRF's) besides the fact that the standard explicitly limits it to position/profile.

Perhaps the standard could include separate pattern creation mechanisms - for example a Pattern of Location and Pattern of Orientation. I remember methods of controlling mutual orientation being discussed at length (

https://www.eng-tips.com/viewthread.cfm?qid=438912)

and one of the old practices was simply placing a double leader on two surfaces with datumless parallelism. As Evan aptly put it:

I would even take it a bit further. I would like Y14.5 to allow parallelism to be specified for a group of surfaces without any datum features. I think that this would capture the real requirement on the OP's part. The two surfaces of the width need to be mutually parallel, but they don't necessarily need to be parallel to their own combined centerplane. They just need to both be parallel to the same arbitrary centerplane.

It seems to me that a provision of a pattern creation mechanism/grouping for tolerances of orientation would solve this - its not just that Y14.5 doesn't provide support for datumless orientation, its that there is no provisions for grouping/patterns of surfaces controlled with orientation regardless of specified datum features. In fact, I couldn't find a single example of orientation specified to more than a single feature at once.

 

[pmarc]

chez311,

In ASME meetings in Fall 2018 in St. Louis, MO Y14.5 committee organized a brainstorming session and literally asked everyone present at that time in the room to throw out ideas (additions, improvements, deletions) that the people would like to see in a future version of the standard. Inclusion of orientation tolerances in the simultaneous requirement rule as well as allowance for datumless orientation were mentioned back then.

Does this mean the concepts will be added to Y14.5-202x? I definitely wouldn't say that.

 

[chez311]

pmarc,

Very interesting, hopefully someone from the committee had their ears on that day. The more I think about it the more I would like to see provisions for pattern creation mechanisms for orientation - be it SIM REQ, nX, or any of the ones mentioned for location in Y14.5-2009 section 1.3.42.

I shan't hold my breath though.

 

[chez311]

pmarc,

Since we're on the topic, what do you think about a directly toleranced width combined with a 2X datumless profile tolerance directed to the surfaces to control mutual parallelism?

 

[pmarc]

I would say that even though this would probably be the best option within currently existing rules, I would personally prefer to avoid mixing profile with directly toleranced dimensions as this could still potentially create a confusion as to whether the profile tolerances don't indeed control spacing between the faces (especially in MBD world where basic dimensions are very often not shown at all).

I would rather like to be able to use something more straightforward (although here some may say that datumless orientation isn't straightforward at all).

Beside, would you have a similar proposal in case of a group of multiple nominally offset and parallel features (flat patterns of features) where the intent would be, for example, to refine orientation between the features within the group?

 

[pylfrm]

As for fig. 4-22, I would say that removal of "2X" would cancel the requirement for mutual location of the surfaces because the pattern creation mechanism would no longer exist.

It seems to me that the figure shows a toleranced feature with a fully-defined true profile (two planar surfaces with identical outward-pointing normal vectors and 20 mm separation), so I don't see why the idea of patterns needs to be involved here. I don't think removal of "2X" would change the meaning.

I may well be missing something here, because I don't really see why the idea of patterns needs to be involved in ASME Y14.5-2009 at all.

I agree that the exclusion of orientation tolerances from SIM REQ always seemed discontinuous to me. I always intuitively felt that there was no real good reason why there couldn't be simultaneous requirements for orientation (ie: no rotation between DRF's) besides the fact that the standard explicitly limits it to position/profile.

Simultaneous requirement as the default is explicitly limited to position and profile, but I don't see anything stopping you from applying the "SIM REQT" notation to orientation tolerances.


pylfrm

 

[pmarc]

pylfrm,
Without 2X, and with the existing definitions of pattern and simultaneous requirement, and with the fact that the profile tolerance have no datum references, the basic 20 dimension is meaningless when it comes to describing the relationship between the two profile tolerance zone. It just describes nominal/perfect condition.

As for usage of SIM REQT, yes this is always an option, but we (chez311 and me) don't really see a reason as to why orientation tolerances could not be added to the simultaneous requirement rule by default.

 

[chez311]

pylfrm,

I agree with pmarc, do you take a different stance that multiple leader lines is not just a "number of instances" notation and imparts a different meaning than the control attached to the multiple leaders applied to each surface separately (per my 6 Feb 20 14:53)?

If not, are you saying that there would be a requirement for the true profile of each planar surface in 4-22 to be basically oriented/located if the control were applied to each surface separately - like the below? If so I'm not sure I agree.

I don't really see why the idea of patterns needs to be involved in ASME Y14.5-2009 at all.

Do you mean just in this specific instance, or generally?

 

[pylfrm]

Without 2X, and with the existing definitions of pattern and simultaneous requirement, and with the fact that the profile tolerance have no datum references, the basic 20 dimension is meaningless when it comes to describing the relationship between the two profile tolerance zone. It just describes nominal/perfect condition.

I realize that the pair of surfaces wouldn't be classified as a pattern per para. 1.3.42 without the "2X", but I don't see anything in Section 8 making that classification relevant.

I figure the simultaneous requirement rule isn't involved here because we are only dealing with one single-segment feature control frame. Regardless of what it's applied to, I wouldn't call it "two or more geometric tolerances".

Aren't the tolerance boundaries supposed to have a uniform offset of 0.4 from nominal/perfect condition, also known as true profile?

I agree with pmarc, do you take a different stance that multiple leader lines is not just a "number of instances" notation and imparts a different meaning than the control attached to the multiple leaders applied to each surface separately (per my 6 Feb 20 14:53)?

I see leader lines (whether single or multiple) as one of several methods available to specify what portion of the part a tolerance applies to.

For conformance to a single tolerance, I'd say there must exist an alignment between actual part and basic geometry that allows the entire relevant portion of the actual surface to fall within the tolerance boundaries. For multiple individual tolerances, I'd say a separate alignment can be used for each tolerance unless they are part of a simultaneous requirement.

I don't really see why the idea of patterns needs to be involved in ASME Y14.5-2009 at all.

Do you mean just in this specific instance, or generally?

I mean generally. I've never felt the need to determine whether or not something is a pattern as defined by para. 1.3.42.


pylfrm