【转帖】section of a section

yang686526

section of a section
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...
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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.
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...
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.
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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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...
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.
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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no trees were killed in the sending of this message, but a large number of electrons were terribly inconvenienced.
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.
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...
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