DATUM "A"

[Michael Boble]

Hello to the entire forum, again I contact you to answer a question about an exercise that I am working on, I would like you to support me by verifying my answers and give me your opinion with number 5 and 6.

The question is:
"Relative to Datum Feature" A ", which Geometric characteristic is appropriate:"
Options:
Straightness, Flatness, Roundness, Cylindricity, Profile of a line, Profile of a surface, Perpendicularity, Angularity, Position and Parallelism

I currently have these answers:
Number 1: Profile of a surface
Number 2: Flatness
Number 3: Perpendicularity
Number 4: Position
Number 5: ??
Number 6: ??
Number 7: Angularity
Number 8: Parallelism
Number 9: Perpendicularity

Thank you all for your support, stay safe !!
(an apology for the image quality, it's the best I could get)
-MB

 

[CheckerHater]

Straightness, flatness, roundness and cylindricity do not require a datum.
Straightness and flatness can be applied to datum feature itself.
Profile of a line, Profile of a surface, Perpendicularity, Angularity, Position and Parallelism are OK.
- you said "perpendicularity" two times
- I like perpendicularity!

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greenimi]

For me the question itself looks a bit confusing.

What (Relative to Datum Feature" A ", which Geometric characteristic is appropriate) is the student expected to know?
Could someone rephrase it a little.... for better understanding (my own).

 

[chez311]

I would highly recommend either the snipping tool or using the "print screen" button on your keyboard instead of taking a photo of your actual monitor. Its somewhat difficult to tell what the different arrows represent.

I agree with greenimi, the question is not 100% clear.

To answer the question, it depends on how we define "appropriate". If it means "correct" ie: for part function, we can't possibly know that on an textbook example part without knowing how its supposed to function. If we define it as what controls are "possible" to apply per their definition, each one has multiple answers - lets assume the caveat that CH noted that straightness, flatness, roundness and cylindricity do not require a datum feature reference so while they can be "possibly" applied to some of these features, lets omit them since the problem states "relative to datum feature A" specifically.

Additionally, the figure has arrows which point to the axis of the holes, FOS. Geometric controls should NEVER be applied to axes, center lines, or center planes but the features themselves - however lets take this to mean instead that the question writer wants us to define specifications for these features which will limit axis variation.

Orientation Controls:
-Angularity can be applied to FOS and surfaces at any angle to your datum feature(s)
-Perpendicularity is a special case of angularity where the feature must be perpendicular to your primary datum feature
-Parallelism is a special case of angularity where the feature must be parallel to your primary datum feature
-All will limit axis/center plane variation when applied to a FOS at RFS, and surface variation when applied to a non FOS planar surface (RFS required).

Position control - can only be applied to FOS. Will limit axis/center plane variation when applied at RFS.

Profile controls (profile of a line and surface) - can be applied to any surface, but if applied to a FOS will only limit surface variation instead of axis/center plane variation.

These in mind, lets look at the options.

1)profile of a line, profile of a surface, angularity, parallelism
2)profile of a line, profile of a surface, angularity, parallelism
3)profile of a line, profile of a surface, angularity, perpendicularity
4)position, angularity, perpendicularity
5)profile of a line, profile of a surface, angularity
6)profile of a line, profile of a surface, angularity, perpendicularity
7)position, angularity
8)position, angularity, parallelism
9)position, angularity, perpendicularity

 

[SeasonLee]

The question is

Season

 

[chez311]

If SeasonLee's excerpt is correct, that certainly changes the answer. But perhaps OP wanted to ask a different question on the same figure.

 

[Michael Boble]

Hey everyone,


First of all, thanks to everyone who has taken the time to answer my question. I appreciate the comments.

I have already asked my partner and he said tha the question that SeasonLee provides is correct (thanks for the support) The options are the ones that I provided in the initial question (and we have the same answers).

I apologize Chez311 if the photography is not of the best quality, I would like to have the image in better resolution, however in this case it is not possible since neither my partner nor I have the exercise, they sent us that way.

So I would like you to support me by verifying my answers and give me your opinion with number 5 and 6. Thanks again!!

-MB

 

[chez311]

If thats the case, I'd say its even less clear what the answer should be in my opinion.

Is the question literally as simple as asking what the angle is in relation to datum A? Ie: 0 deg (parallel), 90 deg (perpendicular), any other angle (angularity)? That seems far too simplistic.

Is the question asking what type of orientation variation does the control already applied to the feature in question limit? If we assume the drawing has a note like "all untoleranced dimensions are basic" (the only way the position tolerances can be considered valid) then there are several features which have no control applied and therefore neither their orientation, location, nor form is limited - I'm looking at (2) and (5). Therefore the answer for these would be "none" and I can't see how the answers for the other features would be anything other than angularity, perpendicularity, or parallelism.

Or is the question asking what specification already applied to the feature in question on the drawing shown impose an orientation constraint/requirement on the feature in question? Its really not clear to me.