Combining ordinate and other dimensions in a single view 2

[rmatthiesen]

I have been drafting for 25 years and have never had this question come up on any of my drawings until now. I have been told that if I use ordinate dimensions anywhere on a sheet, all dimensions need to be ordinate. I have a large part and used ordinate dimensions for 95% of the dims, but I used standard dimensions with tighter tolerances for a couple of features. I have been told that this is bad practice and that if I use ordinate dimensions, they all must be ordinate. Has anyone ever heard of a rule that states this? I have looked in the manuals and have not found a statement that either allows combining dimension types or outlaws it. If there is a publication out their that defines this rule, can someone provide the publication name?

 

[powerhound]

I don't think there is any documentation stating that. I think the bad practice on a large part with many features is to use any dimensioning scheme with no datum structure. I'm assuming you are calling one corner of the part "0" and you are dimensioning all the features from there.

If you mix ordinate dimensions with "standard" dimensioning, you run a higher risk of accidentally double dimensioning some features but that doesn't necessarily make the practice of mixing them wrong.

If no one else here can provide a document to verify your colleagues claim then this may be another example of the ever elusive "industry standard".

Industry standard = still doing things the way my great grandfather did them.

Powerhound, GDTP T-0419
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[drawoh]

rmatthiesen,

I see no problems with combining ordinate on other dimensions on a drawing. If the dimension from hole_A to hole_B is more critical than their absolute position, you are showing your requirement, which is what you should be doing on your drawings.

The bid advantage of ordinate dimensions on a complicated part is that they take up less space, and they make the drawing more readable. This makes it easier to pick out those critical point to point dimensions that you continued to use.

JHG

 

[rmatthiesen]

Thanks guys. I have been part of many different standards through the years and have mixed and matched many techniques. My goal is always a clear and concise drawing, with only one interpretation, that optimizes function and tolerance. I wish my company would embrace the GD&T techniques. This question just wounldn't apply then. I really appreciate the sanity check.

 

[ctopher]

I was told a long time ago that they can't be mixed also (old school).
I found through experience that they can, per other suggestions above.

Chris
SolidWorks 10 SP5.0
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[fcsuper]

I think someone had an opinion about this many many moons ago somewhere. There's no rule against mixing them. As noted above, sometimes it's more critical to override them with a linear dim between two fixtures for tolerancing reasons. Design intend should always take precedent over any dimensioning scheme.

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

 

[KENAT]

So I would lean on the side of it should be avoided unless there's a good reason for it -as it can be a little messy/confusing etc.

However, the reasons given above wrt tolerance and very good justifications for mixing it at least occasionally.

I'll admit, my own personal prejudice is I'm not a big fan of ordinate dimensions - but that is very much just an opinion without even much justification - I just don't like 'em.

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[fcsuper]

KENAT,

Recently, I've been looking over the ISO standard, and also others like JIS. "Dimensions without dimension lines" or as they are known in the ISO standards "Running Dimensions" are becoming more popular, with the number of ways to use them increasing. They can be assigned to polar coordinates (general ISO), and sequential radius dimensions from a common center (JIS) now.

ASME is actually falling behind in this area.

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

 

[KENAT]

Well, I've yet to see a drawing to JIS standards that was was of decent quality - so you aren't exactly convincing me;-).

Actually a lot of ISO drawings I've seen are pretty crummy, but then so too are many that claim to be ASME compliant.

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