QC inspector - pre-qual job test question
QC inspector - pre-qual job test question
(OP)
ASME Y14.5-2009.
Square block dimensioned with +\-. ( height/width/length). Perpendicularity of the side feartures relative to the bottom surface is limited by:
a.) title block tolerance (assuming one is available)
b.) rule #1
c.) answer a or b, whichever is greater
d.) answer a or b, whichever is smaller
e.) not defined ( more information needed).
Same question as above, but drawing implies ISO GPS with NO symbol E attached to the size dimension.
Square block dimensioned with +\-. ( height/width/length). Perpendicularity of the side feartures relative to the bottom surface is limited by:
a.) title block tolerance (assuming one is available)
b.) rule #1
c.) answer a or b, whichever is greater
d.) answer a or b, whichever is smaller
e.) not defined ( more information needed).
Same question as above, but drawing implies ISO GPS with NO symbol E attached to the size dimension.





RE: QC inspector - pre-qual job test question
ISO: ISO 2768 (assuming it is used as title block tolerance)
If title block tolerances are not available, the answer in both cases is "e."
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
And since I am all for learning and developing technical abilities, I would extend/change a bit the above two questions (just for fun) and let’s say if the question (s) were about parallelism (and not about perpendicularity) how the answer(s) will change (if even will)?
Will the answer (s) be the same? I suspect not.
Thank you for your input.
RE: QC inspector - pre-qual job test question
In ASME the answer would be "d."
In ISO still ISO 2768 (assuming it is used as title block tolerance)
And if title block tolerances are not available, the answer in ISO case would be "e."
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
RE: QC inspector - pre-qual job test question
I guess I have to disagree a little bit with your assessment. I know that you have a Senior level certification from ASME and have years and years of GDT experience. However, I am with CH here. If ASME standard is used ( which is the one you are certified anyway) I would say the answers will be a.)- for perpendicularity question and d.) for parallelism.
Per your background: you said. Copy-paste: Thanks for the window into your back round. My background: I have been "around" GDT for over 35 years. I am a machinist by trade (my first exposure to GDT) and a mfg engr by profession. I have never been in a design position. I have a Senior level certification since 1999 and I am the GDT "guru" at my place of work. I have been teaching introductory GDT to companies and colleges in my region for over 30 years. Recently I was asked by our design dept to lead some GDT Case Study sessions to improve the understanding and application of GDT. This has been a challenge and is how I discovered this Forum - looking for some other opinions/approaches to product definition. I too read everything I can get my hands on, but my budget for materials is close to zero. Another reason to tap the knowledge available through this Forum.
RE: QC inspector - pre-qual job test question
I really appreciate these discussions. I am an interpretation and inspection "guy" not so much application. I forces me to think really hard about topics I do not normally deal with.
The stated question only addresses perpendicularity and not parallelism. Rule #1 indirectly controls "parallelism" by "perfect form at MMC size"; however, this is not "true" parallelism as no datums are implied or applied. So I stand by my comment.
The selection of an answer really depends on your belief that Y14.5 "specifies" (directs) one to title block tolerances if direct tolerancing in the field on the drawing is missing. From my limited travels, title block tolerances are limited to size and angles and rarely have default form, origination and/or position tolerance. So I would select (e). But if your travels have exposed you to drawings that do have default form, origination and/or position tolerances the (a) might be chosen.
I have not reviewed Y14.5 to see if title block is mentioned anywhere - busy now - but I will search my electronic copy and respond this week.
RE: QC inspector - pre-qual job test question
In my post from June 7 I was answering greenimi's question about parallelism and not OP question about perpendicularity.
In ASME world size indirectly controls parallelism thru Rule 1. Since title block tolerance is a blanket statement and may be larger or smaller than size tolerance, I chose the answer "d." and stand by that.
When looking thru copy of Y14.5 check out paragraph 1.4 (a):
"Each dimension shall have a tolerance,... The tolerance may be applied directly to the dimension..., indicated by a general note, or located in a supplementary block of the drawing format."
RE: QC inspector - pre-qual job test question
For the ASME Y14.5-2009 version of greenimi's modified question (parallelism), I was initially thinking "b". However, I suppose the stackup of multiple implied 90° angle tolerances could create a more restrictive requirement, making the answer "d". Is this what you had in mind CheckerHater?
After writing the above, I realized the title block could really contain just about anything, such as a statement that would create 30 angularity tolerances for a simple rectangular block as discussed here. This seems like a slippery slope, so I'm going to pretend "title block tolerance" meant "tolerance that applies to dimensions that are not directly toleranced and are not designated as STOCK, REFERENCE, or BASIC" for the questions in this thread.
pylfrm
RE: QC inspector - pre-qual job test question
For fun - TACOM demanded that drawings have no title-block tolerances. Undimensioned right angles are considered 90 degrees but for rectangular plate and blocks the drawings the program I came across had no controls to prevent rhomboid shapes. I guess anything that wasn't perfect needed to be rejected as the angle tolerance was 0. Didn't matter, never inspected.
RE: QC inspector - pre-qual job test question
Imagine drawing of rectangular block with "thickness" dimension of, say, 10 +/- 0.10.
The general note states "UNLESS OTHERWISE SPECIFIED, THE PARALLELISM IS 0.05"
Do you really have 30 choices?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
CH,
- May I know what answer would you choose in your most recent scenario?
- Why did you keep repeating "ISO 2768" for ISO variant of the OP's question? Do you know something that we do not know? For example, that the title block tolerance does not specify angular tolerance directly? Or that the part is made of metal and produced by material removal? What if it is an injection molded cube? Would ISO 2768 necessarily apply then?
3DDave,
Why 12 dimensions only? Why just focus on edges? Couldn't the angular title block tolerance (if specified) be applied to faces too?
My apologies for not giving direct answer to OP's question, but with such poorly worded/constructed question I simply do not want to go into "assuming that this, and assuming that that" kind of stuff.
RE: QC inspector - pre-qual job test question
From the book Fundamentals of GD&T (by Alex Krulikowski) Fig.6-4, both Size and Rule 1 will not indirectly control orientation, so which one is right?
Season
RE: QC inspector - pre-qual job test question
As usual you take my words out of context. I was saying "ISO 2768 (assuming it is used as title block tolerance)"
The full(er) list of options would look somehow like this:
1. Referring to ISO 2768:
“UNTOLERANCED DIMENSIONS PER ISO 2768 –mK-E”
Note: ISO 2768 may have different flavors around the world:
• Brazil: NBR ISO 2768
• England: BS EN 22768:1993 (ISO 2768:1989)
• France: NF EN 22768:1993 (ISO 2768:1989)
• Germany: DIN ISO 2768
• India: IS.2102 (ISO 2768)
• Italy: UNI ISO 2768
• Japan: JIS B 0405 (ISO 2768)
• Russia: GOST 308931-2002 (ISO 2768:1989)
• Sweden: SS ISO 2768
2. Referring to (discontinued) ANSI B4.3-1978:
“UNLESS OTHERWISE SPECIFIED, GENERAL TOLERANCES PER ANSI B4.3 MEDIUM SERIES APPLY”
3. Referring to International Tolerance Grade
“UNLESS OTHERWISE SPECIFIED, ALL UNTOLERANCED DIMENSIONS ARE +/- IT14/2”
4. Referring to International Tolerance Grade (“extended” version):
“UNLESS OTHERWISE SPECIFIED, ALL UNTOLERANCED DIMENSIONS ARE:
HOLES H12, SHAFTS h12, OTHERS +/- IT14/2”
5. Tabulating:
Recreating in part or in whole Table 1 and/or 2 from ANSI B4.3-1978
6. Using single tolerance for all dimensions:
“UNLESS OTHERWISE SPECIFIED, ALL UNTOLERANCED DIMENSIONS ARE +/- 0.8”
7. Using industry-specific standards:
• ISO 8062 – tolerances and allowances for casting: “GENERAL TOLERANCES ISO 8062 – CT12”
• ISO 13920 – general tolerances for weldments: “GENERAL TOLERANCES ISO 13920 – BE”
8. Using country-specific standards:
• DIN 16901 (or newer DIN 16742) – German standard(s) for plastic part general tolerances
• NF T58-000 – French standard for plastic part general tolerances
• NF E02-352 – French standard for sheet metal part general tolerances
• JIS B 0410 – Japanese standard for sheet metal part general tolerances
The list can unfold virtually indefinitely
@SeasonLee:
According to well-respected member of this community, "there are no respectable sources outside of the actual standard"
Are we having fun yet?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
So enjoy
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
Knowing that there are myriads of other ways to specify title block tolerances, as you just posted, I simply couldn't understand why you chose to mention ISO 2768, and not for example ISO 8062.
What about my second question?
SeasonLee,
Please look at the attached screenshot. It is taken from AK's second edition of "GD&T Fundamentals". The highlighted part clearly suggests that size dimension is one of the ways to control parallelism. So which one is right?
http://files.engineering.com/getfile.aspx?folder=6...
RE: QC inspector - pre-qual job test question
That stuff from AK shows why it's sometimes dangerous to try to make general-rule tables and charts. Of course size controls parallelism (assuming it's a FOS, with ASME rules imposed, etc.). But because of those conditions, they couldn't make a blanket statement that size controls orientation.
I have questions of my own on that table, such as why a blanket statement IS made when it comes to profile controlling all four attributes, or how they decided which attributes are "P" or "I" for some of the tolerance rows.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
My choice was purely statistical: for example, in my experience when saying "part" as opposed to "casting" or "weldment" people usually mean "machined part".
So the cast "square block" wouldn't be so square due to the draft angles, hense "(machined)square block"
By my recent scenario you probably mean part with directly toleranced size and general note parallelism.
The answer still "d." - whichever smaller. Naturally, parallelism larger than size tolerance would be meaningless (some would call it "illegal")
It would be inappropriate being actually specified with FCF, but as a blanket "general note" doesn't really hurt.
Have I missed something?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
Some time ago I came up with the part where Profile really does control all four parameters. Naturally it is more of a curiosity from "never say 'never'" domain
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
Thanks for your valuable comments, take a look on my latest version of the book, size dimension disappeared. So, which one is correct?
Season
RE: QC inspector - pre-qual job test question
And now it says "angularity" instead of "parallelism". I wonder if chart for "angularity" says "parallelism" (and has words "size dimension")
This is too much fun (or are we serious now?)
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
No size dimension on angularity chart.
Season
RE: QC inspector - pre-qual job test question
Thanks all
Season
RE: QC inspector - pre-qual job test question
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
Yes, I meant part with directly toleranced size and general note parallelism. So if the general notes states "UNLESS OTHERWISE SPECIFIED, THE PARALLELISM IS 0.05" doesn't the +/-0.10 size tolerance together with default Rule #1 fall under UNLESS OTHERWISE SPECIFIED and override that general note?
J-P,
What can I say beside that I couldn't agree with you more.
RE: QC inspector - pre-qual job test question
I really don't see it that way. They must be satisfied together / simultaneously, so it must be less than 0.10 and less than 0.05 at the same time.
If they contradict each other, then, yes, size tolerance overrides general note. Do you have reference to support your point?
@pmarc & J-P:
Don't you guys think that the idea of "blanket statement" is to show ALL the possible situations?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
(I can show you an instance where that is true, but I wouldn't teach that as "blanket" statement about angularity in a textbook!)
My main issue was with the "P" and "I" in the chart given by SeasonLee. Why would one of profile's primary jobs be to control size?
And yet on the same chart, the runout symbols are parsed into P and I without similar logic.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
I totally agree that angularity controls perpendicularity. In fact, both parallelism and perpendicularity are just cases of angularity and can be abandoned and replaced by single control.
I always believed that primary function of profile is to control, well, a profile! Something like shape of a wing or turbine blade.
But the wing has a thickness and length of a chord, which are... sizes! So how you control wing without controlling size(s)?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
You may recall that some websites promote using position on a single hole relative to only a perpendicular plane. Yet since that is only controlling perpendicularity, it is incorrect since it fails to fulfill position's primary function of location. Different topic, I realize, but it still speaks to the great misunderstandings out there regarding direct vs. indirect effects of certain GD&T symbols.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
I totally agree with your approach to profile and its fundamental control. When I teach, I state profile is used to control the shape (form) of non-standard shapes - those that are NOT flat, straight, circular or cylindrical - shapes that common machine tools produce. I then show them products that have non-standard shapes - auto bodies, aircraft fuselages, boat propellers, etc. and ask how do you control the form of these shapes. It gets the point across. I have an overhead projector and put my hand on the platen and let the shadow of my hand create a profile on the screen. I trace my hand with a marker and ask them to dimension it so someone can make a glove from a drawing. Eyes are wide open. We then get into 3D models to define non-standard shapes. I then add datums to show how they add orientation and then location by constraining motion.
RE: QC inspector - pre-qual job test question
RE: QC inspector - pre-qual job test question
6 datum features and 5 angularity tolerances (one for each other face) referencing each datum feature gives a total of 30 tolerances (effectively 24 perpendicularity and 6 parallelism). I'm sure your example is more likely to actually show up in a title block though. I've seen similar requirements involving runout before.
I generally agree with your interpretation of "UNLESS OTHERWISE SPECIFIED". To count as otherwise specified, I think you'd need either a note that effectively states "the general tolerance does not apply here" or another tolerance of the exact same type, with identical modifiers and datum feature references if applicable, and a different tolerance value. In my experience this is a topic of much disagreement though. It seems even more problematic when CAD models get thrown into the mix.
3DDave,
TACOM probably has a good point. The tolerances never get checked, so remove them and dispense with the fantasy. Did they switch to a note such as "UNTOLERANCED DIMENSIONS ARE BASIC"?
pylfrm
RE: QC inspector - pre-qual job test question
Making them basic would not help - almost no FCFs or datums.
RE: QC inspector - pre-qual job test question
Now since the OP is still keeping silence (but, I guess nobody asked him/her anything, and honestly probably he/she is confused too on what is the “correct” answer) I will jump a bit into this discussion and try to get back to the main subject. I am doing this because I was the one to extend the original OP question from perpendicularity to parallelism (just for my own education)
Therefore, considering a title block defined like:
.X ±.05
.XX ±.01
.XXX ±.005
.XXXX ±.0015
ANGLES ±30 MINUTES
INTERPRET DIM. AND TOL. PER ASME Y14.5-2009/ ISO GPS --as applicable
What would be the “best answers” for the questions regarding the perpendicularity (OP question) and parallelism (my question –extended subject)
Do we agree that the answers would be:
Perpendicularity:
ASME-2009 a.)
ISO e.)
Parallelism:
ASME-2009 d.)
ISO e.)
Pmarc,
I probably agree that the OP question is poorly worded, but I guess we have seen very weak questions on the GDT books—different authors, GDTP preparation tests or even at the ASME exam itself, right? No excuse, for the OP, just a little bit of compassion/credit…And I know, that two wrongs does not make it right.
RE: QC inspector - pre-qual job test question
I would agree that perpendicularity answer for ASME will be "a." and parallelism answer "d." providing that envelope requirement is default and some sort of T/B tolerances is provided.
Now, as pmarc mentioned, given several different ways general tolerances may be specified in ISO/metric, the situation may require more careful consideration: what kind of tolerances are actually specified?
ISO Sub-case 1: Nothing is specified. The answer is "e." for both perpendicularity and parallelism.
ISO Sub-case 2: Envelope requerement is specified. The answer is "e." for perpendicularity, "d." for parallelism
ISO Sub-case 3: Drawing shows title block tolerance based on number of decimal digits like in your example. I personally dislike the idea, as leaving trailing zeros is forbidden in both ASME and ISO metric practices by default.
But I think it was Belanger, who argued that note actually qualifies as being "specified otherwise", so it may override default requirement. I still don't like it, but have to agree that he has a point.
So, if no other general tolerances are specified, the solution may be "a." for perpendicularity, "e." for parallelism.
ISO sub-case 4: separate document is referenced. We will use ISO 2768 as an example (sorry pmarc)
Are we having fun yet?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
I already started to dislike ISO—and its lack of configuration management--, but that does not mean that I am in love with ASME (or at least not yet).
RE: QC inspector - pre-qual job test question
Maybe i will stop liking it too?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
RE: QC inspector - pre-qual job test question
This is taken from the new draft of Y14.5, but I am more than sure that I saw this also in one of the other, already published, ASME Y14 series standards (I think it was Y14.41, but it would be great if someone could confirm):
"1.4.9 Unless Otherwise Specified (UOS)
The phrase "unless otherwise specified" or UOS is used to indicate a default requirement. The phrase is used when the default is a generally applied requirement and an exception may be provided by another document or requirement."
The way I see this definition in case of your scenario (and in general) is following. The parallelism 0.05 is the default requirement. Since the "thickness" dimension tolerance +/- 0.10 = 0.20 together with Rule #1 is capable of creating parallelism requirement for opposed faces, the exception to the default requirement has been created.
------------
I agree, there can't be an edge without two faces. I also agree that the number of alternatives grows significanlty for anything but a simple block. And that I have also never seen an inspection report the bare minimum.
But I do not agree that each edge represents an angle between two faces. An edge is just an intersection of two faces regardless of the angle between those two faces. The two faces can be perfectly perpendicular to each other, or be at any angle to each other, say 60 degrees, and the common edge will be exactly the same for both cases.
If we take 3 faces of a rectangular block into consideration (the bottom face, and two side vertical faces) that all have a common point (single corner), the situation is similar. All 3 edges generated by these surfaces can be perfectly perpendicular to each other, however the faces may not be at right angles.
I challenged your initial statement about 12 dimensions to check not because I wanted to point out that you were wrong, but because I wanted to show that the title block angular tolerances (which, unfortunately, are still very common in industry) are so vague that it is even not clear what to check. Do you agree?
RE: QC inspector - pre-qual job test question
I'm not sure how this can be true. If all 3 edges are mutually perpendicular then that controls 6 degrees of orientation. 3 of those are redundant because each edge lies on 2 faces, leaving the remaining 3 degrees applied to making the faces perpendicular to each other. I'm sure there is a more rigorous proof.
I don't see how the interpretation of title block angle tolerances applied to implied right angles is vague. The general angle tolerance applies to all untoleranced angles and anything that appears to be at right angles is assumed to be 90 degrees. Since they are not explicitly dimensioned these right angles are not explicitly toleranced.
So, every pair of nominally perpendicular faces and every axis that is nominally perpendicular to any set of faces and vice versa is a candidate pair to be inspected. It's no wonder inspectors ignore the requirement.
RE: QC inspector - pre-qual job test question
Size does not create exception to default requirement, because it doesn't contradict the default requirement. Although I really stop caring at this point.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
It is a pitty that you stop caring, because in my opinion knowing how to deal with UOS type of notes is really important - not only for this particular thread, but in general.
We will stop here, if you like, but the last thing I would like to understand is why you think that the size + Rule #1 combo, which creates indirect 0.2 parallelism requirement, does not contradict the default 0.05 parallelism note. Is it because you think that the default parallelism note is actually a refinement of 0.2, and as such should be met addtionally to the size/Rule #1 requirement?
3DDave,
Please take a look at the attached picture. This is my attempt to visualize what I meant in my previous post.
http://files.engineering.com/getfile.aspx?folder=d...
RE: QC inspector - pre-qual job test question
If I have Size tolerance .10 and parallelism of .05 represented by FCF, does size tolerance override FCF?
If I apply parallelism FCFs to everything that nominally appears parallel, will they be overriden by sizes?
If I replace several FCFs with one single note, what does it change?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
The diagram is showing as-manufactured variation. It does not relieve the inspector of measuring the angle across the edges as described. The measured angle will vary just the same as any other raw measurement.
RE: QC inspector - pre-qual job test question
No, they will not.
If this single note does not use "UNLESS OTHERWISE SPECIFIED" (or similar wording), it changes nothing. But if "UNLESS OTHERWISE SPECIFIED" is used in that note, that changes everything, as I tried to explain above.
Oh, by the way. You asked me for a reference to support my point. I gave you one that in my opinion does the job. Could you in return offer a reference to support your point?
-------
The point of the diagram was not to say that the inspector is relieved of measuring the angles across the edges. It was to show that measuring across the edges may in some cases give false impression about actual geometry (in this case perpendicularity) of as-produced faces. Another, and probably more important, point was to re-emphasize that relying on title block angle tolerances may lead to serious product quality issues. If there is no clear agreement on what to measure (and I think our conversation is a good evidence of that), this is well enough to say that during inspection the same issue, if not bigger, will happen.
RE: QC inspector - pre-qual job test question
RE: QC inspector - pre-qual job test question
Your quote doesn't say anything. It replaces one term without definition with another term without definition.
I am tired of arguing about the obvious with people in denial.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
I just hope that this discussion showed at least a bit that an obvious thing for one person does not have to obvious for someone else. And moreover, that the someone else's point can be valid unless proven otherwise.
------
3DDave,
I am glad you think that so far I have shown nothing to disagree about. I am not sure what else I could say to better describe what I am up to here without repeating myself.
To close this topic, I would like to emphasize my firm belief that using title block angle tolerances in a form of "ANGLES ±30 MINUTES" notation (or similar) is in most cases like asking for troubles. For implied angles it is mainly because it is unclear as to which angular relationships they should be applied to and in the end in reality nothing is measured (I think here I could agree that this is rather the implied dimension concept's "fault"). For explicit angles without individual tolerance indication it is because of inherent ambiguity of the directly toleranced angle dimension. The way to eliminate this ambiguity to some extent would be to use origin symbol at one end of angular dimension, but how many drawings with origin symbols applied to angle dimensions have you seen? I have seen very few.
RE: QC inspector - pre-qual job test question
Re:"If this single note does not use "UNLESS OTHERWISE SPECIFIED" (or similar wording), it changes nothing. But if "UNLESS OTHERWISE SPECIFIED" is used in that note, that changes everything, as I tried to explain above."
On my replay on June 10, I did not use the verbiage;"UNLESS OTHERWISE SPECIFIED"
My statement--copy-paste:
"Therefore, considering a title block defined like:
.X ±.05
.XX ±.01
.XXX ±.005
.XXXX ±.0015
ANGLES ±30 MINUTES
INTERPRET DIM. AND TOL. PER ASME Y14.5-2009/ ISO GPS --as applicable "
Am I a little bit safer from "multiple legal interpretations"? Just curious.
And by the way, how would YOU answer the OP question and also my "extended" question if no UOS note is used?
If you prefer to not give me an answer (and the answer would be read as "in/with all practical purposes) I am perfectly fine with that. I do understand your point (about UOS) and I think it is a valid one and you don't want to promote in any size, shape or form incorrect/not valid material/advice on this forum. I perfectly understand that if only one time you are not consistent/consequent the horse will jump the fence.
RE: QC inspector - pre-qual job test question
You argue that dimension can override orientation control due to Rule 1.
You know better than me that RULE 1 CAN NEVER CONTROL RELATIONSHIP BETWEEN TWO FEATURES, EVER!
You chose to ignore the most fundamental rule of GD&T just to settle personal score; this is what I call "denial". I will gladly accept better term if you come up with one.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
Your answer was following:
The answer "d" in the original question is following:
where:
a,) title block tolerance (assuming one is available)
b.) rule #1
So on June 7th you claimed that rule #1 might control features parallelism (if smaller than title block tolerance), but today you are saying:
May I ask what changed in between? Or you know what... I do not really want to know, because I have a feeling that you will come up with another interesting explanation that definitely will not bring us any closer to solve the UOS note dillemma.
Nevertheless, thank you for this interesting and (still) funny dispute.
RE: QC inspector - pre-qual job test question
Please allow me to leave your question unanswered.
I already regret that I jumped into this discussion with my side questions.
RE: QC inspector - pre-qual job test question
I am always having hard time to distinguish if people are honestly misunderstanding, or intentionally distorting the truth. But I'll bite.
This is another thing that you know better than me.
Rule 1 is INDIRECT control acting when any other control is ABSENT.
You argue that Rule 1 is overriding DIRECT control that is actually PRESENT.
Do you honestly cannot see the difference between the two? I have to agree with you - it's really funny.
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: QC inspector - pre-qual job test question
One is not better than the other, they are just different.
Therefore, in my opinion, discussions as such, will help many, many, many people to understand the fine details of the drawing dimensioning in general and relationship and/or agreement/conflict of the standard with their own imposed title block tolerances. So, no, not ever regret you guys jumped with both feet into this discussion. I think you helped tremendous number of otherwise “unaware” and “silent” (for this discussion point of view) people. In fact, that is why you fine gentlemen came here on this forum in the first place, don’t you? You guys fulfill the purpose on why this forum exist in the first place: To help people. And you did. THANK YOU!
RE: QC inspector - pre-qual job test question
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: QC inspector - pre-qual job test question
We didn't even touch on the fact that if the section is rhomboid, there are unopposed surfaces. Sigh. Those are always the best red herrings. Fresh canned.
RE: QC inspector - pre-qual job test question
I am relatively new to the forum world. I must say I am completely blown-away with how the discussion progressed and how it "ended", especially greenimi's post. Real professionalism here!!!
I would like offer a non-technical observation: The disagreements as to how to apply block tolerances and their questionable interpretation promote nothing but non-productive, profit robbing time. I have seen way too many arguments on the shop floor where Mfg made a "good" part and QA labeled it "bad" based solely on the application of block tolerances. They then call Engineering to resolve the conflict who has no clue as to what the limits of functional acceptably are - the Engineer copped-out and just defaulted to the title block. Meanwhile the machine tool, at $150 / hour, sits idle while the three posture. Had the design been "studied" by Engineering to define the limits, and had GDT been applied to communicate them, the "argument" would never have occurred and the machine tool would have kept running and the part delivered on time.
Continuing: this post again confirms my belief that tile block tolerances, if used at all, must be limited to the size tolerance on features-of-size and should never (attempt to) define default relationships between features in any way. Meaningful relationships between features require specified datums (reference frames) and, in my opinion, due to the almost unlimited possible relationships, it is not realistic to define default datums in a title block or any other document. Any relationships between features must be specified on the field of the drawing with the appropriate controls.
RE: QC inspector - pre-qual job test question
The problem to gaining agreement is that not all of the people in that discussion have the background to make the decision.
What is most telling is that QA should have been involved in the selection of a process to make an acceptable part before the machinist even got the task. The machinist should be able to produce a history for similar parts or similar features as a guide to what they can do, to QA so they know ahead of time if the part will likely be acceptable within a good margin. And QA should discuss the proposed measurement setup with Engineering to see if it is going to be performed as expected.
Why not involve Engineering with the manufacturing discussion straight-away? Because the drawing is of an acceptable part, not a manufacturing drawing and QA is charged with accepting or rejecting the parts. If the part is made out-of-house, there may not be any manufacturing to have a discussion with.
Neither QA or manufacturing should have any say about what the part does, unless the entire system is being analyzed, as sometimes small tolerance for variation in one part is to allow more tolerance for variation in a mating part or to remove assembly variation that installation techs would have to make up.
Applying FCFs (plus-minus -is- GDT) is no guarantee. I have discussed with an inspector who believed that a chained set of basic dimensions meant that the hole (in this case) was to be measured for location from the nearest chained feature, and not the datum in the FCF, because "that's what the engineer meant." I asked if he'd called the engineer, but this guy was a mind reader and didn't care to make that call.
So far I have not seen any example of a drawing where it is unclear what should be inspected simply because of title block tolerances. It doesn't matter if the tolerance is co-located or in a note or in the title block as long as there is a method to determine which is the correct tolerance to apply.
My suggestion is not that title block tolerances are good or bad, but they have exactly the same flaws as applying the same tolerances to explicitly applied linear and angular dimensions. And recall, where a 90 plus-minus assumed angle relation is replaced by a 90 degree basic relation when using an FCF, the problem of determining where the 90 degree angles are is not entirely eliminated.
RE: QC inspector - pre-qual job test question
I was hoping for other perspectives on title blocks. Much appreciated. I don't have time right now to compose a response but I intend to in the near future.