Section of a Section 3

[KENAT]

Where is it in the ASME drawing standards that it says you shouldn't have a 'section of a section'.

I thought it would be in Y14.3 but I don't see it. I'm sure it's come up on this forum before but a quick search didn't show it.

Or am I making this one up;-)

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

ASME Y14.3M-1994 para 3.2.4
"The cutting plane should be shown through an exterior view and not through a sectional view."

Of course, it says "should" so I guess that, while it may be preferred practice, it is still not mandated.

 

[KENAT]

Thanks ewh, I have ASME Y14.3-2003,

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

Not sure how I missed it, agree on the pesky 'should'.

Star for you.

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

Thanks!
It looks like I'm falling behind the current standards.
I think I'll wait until 14.5 is officially released before I ask for new ones.

 

[wes616]

Keep in mind that the standard is written in such a way as to not explicitly forbid additional sectional views from being used, if they aid in fully defining the product.

I find I often use sections of sections when making assembly drawings. Often it is unavoidable.

Wes C.
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[KENAT]

Rules/Laws are for the obediance of fools and the guidance of wise men, got it.

However, one issue with a section of a section. Should the section of the section show a projection of only the part 'left' after the section, or a section of the complete part at that point.

While I've been tempted, I don't think I've ever done it. I've always found it can be avoided.

However as you point out, the standard doesn't explicitly forbid it.


KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

I have yet to come across a situation where a section from a section is unavoidable. It is much like crossing dimension/extension lines; with effort, a solution can usually be found that doesn't break the rules. Admittedly, sometimes it is not worth the effort required, and judicial exceptions to the rules are ok as long as intent can still be clearly communicated.

 

[wes616]

OK ewh,

You've got me there. It is never truely unavoidable. I will say this though. I have found that while trying to stick to the rules explicitly, I often end up with a more confusing drawing.

Here is my example, where I will try to explane with words, since I don't want to take the time to draw it out....

I have a box that I install in an aircraft. The box is screwed into a clip from the inside. Firstly I have to point to the box to call it out in the installation. Then I take a section of the box to show the fasteners, how the holes are drilled and whatnot. I also would like to show how the fasteners stack up because there exists a shim, and it isn't immedatly apparant where it is placed in the installation of the box. I have two choices, I can go back to the original view and take another section 90 deg to the previous section, or I can take a section of a section.

I find that, in dealing with the fabricators doing the work, that there is often less confustion about what the drawing is attempting to achieve by showing a section of a section.

I guess the point is, if you are consistent, and conservative in your uses of "breaking the rules," and you do it specifically to address some a particular problem, then you'll probablly be ok. If you do willy nilly, whatever you want, you're just a some hack who should probablly go back to middle school and get some drafting instruction from someone who'll hand you a pencil, not a computer mouse.

Wes C.
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[ewh]

My point exactly, Wes. That is one bright spot in the revised standards, that you "should" follow certain practices, but are not "required" to do so. As always, the purpose of a drawing is to CLEARLY and concisely define something.
What really frustrates me is seeing a simple drawing where many rules are broken for no good reason other than laziness or lack of thought put into it.

 

[KENAT]

Yeah, I'm affraid Wes that round here if you let something slip once it becomes very difficult to enforce it in future, so I'm sometimes a bit draconian.

As you say, most of the people around here would benefit from some drafting classes.

Personally, especially with the functionality of our CAD system, I've been hiding parts, with a note under the view saying which are hidden, a lot more lately. For assemblies where you basically have a bunch of stuff in a box then it works pretty well, just hide the lid or something rather than sections.

If I'm breaking the rules let me know;-)

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

Well, interpretation is open here. I would suggest that the "should" only refers to the comment of where to put the section plane. Where not to put it is clearer, with a direct command. It's doesn't say "...and should not be through a section view." It says "...and not through a section view."

Anyway, just playing devil's advocate.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[ewh]

I disagree, because there is no other choice of views other than an exterior view or a section view. If it is only suggested that exterior views be used (as it is), then to do otherwise would mean using a section view. To command no section view use would also command exterior view use only.

 

[ctopher]

I never have made a section from a section. I will find another way to show the details.

Chris
SolidWorks/PDMWorks 08 1.1
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[KENAT]

fcsuper, I'd love you to be right but sadly I don't think you are.

I'm opposed to section of a section not just because of what the standard says but for the reason I put above.

However, it isn't completly forbidden although I've never found a situation it couldn't be avoided though.

KENAT, probably the least qualified checker you'll ever meet...

 

[ringman]

wes616

Have you considered a cutaway on the box that would show the heads of the fasteners? Then you could take a section thru that view of the fastener.

 

[CheckerRon]

My thanks also to EWH for that ¶ 3.2.5 reference on Section of a section in Y14.3. This is the pet peeve of mine (and anyone who started out on the drafting board, but I had not found that ref.
Yes, there is that wishy-washy ASME committee "should". Those guys just can't take a stand for what is right, for fear that someone, somewhere might object. I miss the definitive and contractural "shalls, musts', and wills'" found in the old Mil specs that precluded arguements.

 

[ewh]

Ah yes, a complete level 3 data package. Those were the days when you knew what was expected. If you had doubts, everything was spelled out in the contract and the specs.

Believe it if you need it
or leave it if you dare

 

[fcsuper]

There are other types of views, though arguably, some are types of others. For example, it's usually bad pratice to place a section cutting plane through a pictorial view (Isometric or similar). So, it isn't true the standard is making a an exclusionary statement that is only mentions the only other possibility. There are other possibilities not mentioned.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

An ordinary old iso view is an exterior view. The standards says exterior, not orthographic.

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

Has anyone run a section cut plane through a pictorial view? Mostly curious.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group