Dimension to Background Lines in a Section View 7

[flash3780]

Quick question: Does it violate standards to dimension to a background line in a section view?

In my view, it's bad practice, but I'm not sure that it's explicitly disallowed by any standards. We do our drawings in accordance with ASME Y14.5-1994. Unfortunately, I don't have my copy with me at present.

Thanks for the help.

 

[flash3780]

I'd say dimension the depth in Section B-B.

Section B-B was added in the last revision to do just that. I think it's much clearer that way. A composite section A-A (with a knee in it) would also work, I think.

From the sound of things, the initial detail wasn't illegal. Still, I think that it's much clearer this way.

 

[KENAT]

So I go back to my initial comment after you posted the first version. The dimension itself is perfectly fine.

However, if within context of the whole drawing it could be confusing then that should over ride matters and may give cause to either crank the section line through the slot or add an extra view. Like ewh kind of said.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[SteveMartin]

I think disallowing lines not in the plane of the section cut is much too harsh. Depending on the section it may be more or less clear. My practice is by default to show what you call 'background lines' (and dimensioning to them is fine, too), and add a note the view if I do not show them.

 

[flash3780]

My practice is by default to show what you call 'background lines' (and dimensioning to them is fine, too), and add a note the view if I do not show them.

I think that [tt]BACKGROUND FEATURES OMITTED FROM SECTION A-A[/tt] or something along those lines would be a valid note. The reason for not leaving them in is they sometimes tend to clutter things up without giving added information. In my mind it's often a bit cleaner to omit them.

Really, though, it sounds like a matter of preference and style, rather than one of standards.

 

[pmarc]

For "background" lines visible in cross-sections Y14.3M-1994 gives something like this:
"3.6.1. Visible Lines. Visible lines behind the cutting plane are generally shown. Selected lines may be omitted if greater clarity is gained."

I haven't found anything in any standard related to dimensioning of "background" features in cross-sections, but IMO this is acceptable and very often indispensible practice.

The only situation (that I can imagine at the moment) where I would not go for such dimensioning is for features that are visible in a background of cross-section but are not in the same projection plane as cutting plane.

 

[powerhound]

I don't think it's a good idea to turn off the background lines in this case. I also think the dimension is fine as originally presented. The lines do not obscure anything and they are an accurate representation of what the part looks like from that view. Turning the lines off won't clarify anything.

I have seen cases where turning tangent lines either on or off makes a view more clear but I don't think I've ever seen a case where removing lines representing actual features did more good than it caused confusion. I always expect any view to accurately represent what the part will look like. I agree that excessive dimensions in one view can make a cluttered print but that's not the case here.

If you look at the parent view in the first print you provided, there is no dimension for the OD, ID, or counterbore. Will turning off the lines to those features in your parent view make the drawing more clear since those lines aren't "adding information"? To me, it would be a much more confusing print. I just don't think it's a good idea to turn off lines depicting features. I'm sure there are some cases where it makes perfect sense but this isn't one of them. I think that hiding feature lines should be more the exception instead of the rule.

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