Section of a section view & section view as base view - Bad practices? 8

[aroy1984]

That taking a section of a section view and using a section view as a base view to project other views is bad drafting practice (except where unavoidable) I have been told often.

But are there any official standards out there which expressly say that such a view is wrong/not to be encouraged? Any specific reasons (logic wise or engineering wise) why these are bad practices?

 

[CheckerHater]

No, there are no standards that are explicitly forbidding that.

Also, there are no logic or engineering reasons against it.

In fact, logic of engineering practices suggests just the opposite: Your "base view" is supposed to be the most informative representation of the part.
If section is the most informative view, then so be it.

I am including picture borrowed from the drawing manual that is using this "bad practice":

 

[CheckerHater]

I will have to agree that making section of a section should be considered "bad practice"

Although, in SOME cases it MIGHT be the only way around, like adding changes to already established big and busy drawing.

Either way it still a matter of personal preference, the realm of "may" and "should"; certainly not "must" or "shall".

 

[JNieman]

For turned parts, the "Base View" is often a section view when it is a part completely, or mostly, turned on a lathe. A section view is going to have the VAST majority of the information on the part, and an end view may not even be needed after that, if one were to be "stingy with the ink".

I don't believe making a rule would be advantageous to this topic because the "exceptions" are so numerous and common that they start to not become so exceptional.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[ewh]

I agree that it is bad practice, with few exceptions. It is also bad practice to take a projection from a section view, and many CAD systems do not allow the direct placement of such views - instead of a direct projection, another appropriate "base view has to be added and aligned with the section.
The reason, as far as I can ascertain, that it is considered "bad practice" is that it provides the opportunity for mistakes and mis-interpretations and can cause ambiguity as to whether to show the geometry that is taken away in the section in the following section. It can also add confusion as to what exactly it is that you are looking at, especially if taken to extremes such as a section from a section from a section.

ôKnow the rules well, so you can break them effectively.ö
-Dalai Lama XIV

 

[KENAT]

The cutting plane should be shown through an exterior view and not through a sectional view.

Unless I'm missing something this effectively precludes section of a section.

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[TheTick]

If my view of most interest is a section view, I put the base view on the sheet in small scale, so that there is context for the section line.

SolidWorks will allow a section-of-a-section. Maybe not "legal", but it's possible.

 

[ewh]

Thanks, KENAT! I had thought I had seen that somewhere, but am getting lazy. ;-)
It is ¶8.2.5 in the 2012 edition.

ôKnow the rules well, so you can break them effectively.ö
-Dalai Lama XIV

 

[KENAT]

thread1103-205514
thread1103-191012

touched on this previously

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[ewh]

ah, the memories...

ôKnow the rules well, so you can break them effectively.ö
-Dalai Lama XIV

 

[aroy1984]

Thanks, folks. Your replies have been a big help in a running 'battle' I am currently engaged in.

The specific examples in which I have seen the use of a section of a section and section view as a base view are unfortunately examples of lazy draftsmanship. To top it all, the person who made them insists that such a rule is not mentioned/suggested in any standards.

The ASME quote on section of a section is pure gold for me in this context. Now if only I could find something similar on the unnecessary use of a section view as a base view.

 

[KENAT]

aroy, take a read through that standard, you may find something else to help - but I can't promise it.

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[Belanger]

Although there is a difference in the standard between using the word "should" and using the word "shall."

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

 

[ewh]

... just seems like a lot fewer "shall"s than there used to be.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[KENAT]

Belanger - that topic is done to death in at least one of the older threads I linked to.

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[Belanger]

Thanks, Kenat. But I was replying to your earlier post that the "should" statement "effectively precludes" doing such.

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

 

[KENAT]

That's what I was talking about the implications of 'should' are discussed in at least one of those earlier threads.

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[TWJR]

It is also bad practice to take a projection from a section view...

That other thread you linked to talks about that... as a checker, I've had numerous discussions with drafters about this. Plenty of them make a section, then project to a full view. Bad practice, yes, but even if it weren't, seems to me, using the logic of orthographic projection, if one were to make a projected view from a section view, that view would appear "cut in half", not full. Have no idea why one would want to do that.

 

[ewh]

That's the ambiguity I was referring to.
I have tried to follow "local" practices when I first started this position, and sections from sections was one of them. I quickly realized how easy it is to get lost in a complicated model and end up drafting something far different than intended, just because it was so easy to get lost in the model relative to where the sections are "supposed" to be coming from. I now try to avoid such local practices whenever possible.
Fortunately, this company is doing it's best to follow ASME standards; unfortunately, it still takes exception to the section from a section rule.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[CheckerHater]

if one were to make a projected view from a section view, that view would appear "cut in half", not full

Where people get ideas like that? Then, if we project from the view that has "broken-out" section, do we show chunk of material ripped out of the part?