General Dimensioning Question

[ewh]

You have a box, with three identical tabs welded to the top, extending up. These tabs are aligned in profile in the side view. When dimensioning them, do you dimension the profile using single dimensions, or do you add "3X" to the dimensions?
I had been taught that if it was obvious from the other views that there were aligned, you do not add "3X" as you were dimensioning the profile, not the individul tabs. I can't locate where or if this is addressed in ASME Y14.5.
TIA!

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[KENAT]

Would it come down to the problem of 'assumed alignment'? Just because features are shown aligned there is no implicit requirement for them to actually be aligned, there needs to be a tolerance given some how?

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[ewh]

There is only one tab outline visible in the side view, which indicates that they are aligned (so it is as shown, not assumed), and the other views show the additional tabs and their spacing.

“Know the rules well, so you can break them effectively.”
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[KENAT]

ewh, my point is what is the tolerance on how aligned the 2 tabs in the rear are with the one in front that is actually dimensioned?

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[ewh]

The same tolerance would apply. The dimensions define the profile, and as long as all of the tabs fall within the dimensional tolerances, it is good. It would not matter if one tab fell at the low end of the tolerance and the next at the high end.
One way around this would be to dimension and use extension lines in the other views that show the tabs, but I am checking a rather busy drawing and didn't want to make it busier.
See attached.

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

 

[CheckerHater]

First, it’s 4X, not 3X.

Second, if it was not 4 tabs, but 4 holes aligned in the side view, would you be satisfied with Y14.5 Fig.7-44?

 

[drawoh]

ewh,

I can interpret your drawing as shown, but 4X makes everything absolutely clear.

--
JHG

 

[ewh]

CH,
Sorry about the "4X" vs "3X"; this was just a quick pic to describe the situation. That figure (and others in that section) does make it a bit clearer for me.

JHG,
I have to agree... the drawing should not contain any assumptions.

Thanks!


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

 

[CheckerHater]

No need to be sorry, I didn’t mean to be harsh on you
I used to work on 2 CAD systems, one would make array of 4 features, another 1 feature and 3 “copies”.
It was constant “what? How many?”
Good thing we are on the same page. Using multiplier makes it clear and doesn’t take lot of drawing space.

 

[KENAT]

ewh, the same tolerance might apply at MMC because profile would be interrupted, but what at the low end? I'd say you need the 3X/4X to cover that (or a geometric permutation).

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[drawoh]

...
Second, if it was not 4 tabs, but 4 holes aligned in the side view, would you be satisfied with Y14.5 Fig.7-44?

In SolidWorks, when I am dimensioning hole patterns on my designs, I dimension to the furthest hole away. The dimension line crosses the other centre marks and holes. If, for some reason, I cannot do this, I dimension to the nearest hole and I apply the quantity of holes that line up.

Recently, I was making fabrication drawings of someone's rather sloppy models, so I used SolidWorks' linear centre marks, rather than their single ones. When this features draws the connecting lines, I assume that stuff lines up.

--
JHG

 

[Tenkan]

The easy answer is clarity... if the only thing defining the location of the three tabs is a dimension in their profile view then place "3X" or similar with the dimension locating them. But if in the top view the tabs are aligned with a phantom line, or there is anything elsewhere (note, datum...) in the drawing indicating they share the same nominal position then 3X is optional.

I was taught that clarity overrides standards. Some drawings are so busy its hard to distinguish feature positions that are very close and sometimes a note (eg: "TO .350" TALL TABS, 3 PLACES") saves creating sheet 2 for only one more detail view you couldn't fit on a one page drawing...

lightweight, cheap, strong... pick 2