Polar Equivalent to Ordinate Dimensioning in Conjunction with 14.5?

[IntolerantofApathy]

Hi,

Does anyone know why polar equivalents to Ordinate Dimensioning is neither described by 14.5, nor included in common solids modeling drafting packages? To clarify my question, please consider scenarios where a design requires multiple angular dimensions. On a drawing, situations like this occupy a lot of space on the page because multiple dims create successive, concentric arcs. These can become particularly space wasting when angles exceed 90°.

In the world of rectangular coordinates, "busy" drawings appear less cluttered through the use of ordinate dimensioning. Moreover, I've never seen a limitation for using GD&T in conjunction with ordinate dims (features controlled by GD&T can use basic (but ordinate) dims as long as datums are established and feature control symbols accompany them). And the CAD packages I've used (Creo/Pro/E, SolidWorks, and Siemens NX) enable ordinate dimensioning. On the other hand, I don't believe such capabilities are integrated for polar dimensioning within any CAD packages I've seen.

Obviously, there are designs that are best conveyed using polar dimensioning. And, since the accuracy of angular dims gets progressively worse with +/- dimensioning (for example, a +/- 0.5° angular tolerance will generate twice the positional accuracy when a feature's location from the center of the polar array is doubled). In my opinion, this goes away with GD&T because the perfect location can be conveyed by basic dims and true position controls the accuracy. And, if the polar equivalent to ordinate dimensioning were available, the nuisance of successive arcs eating up the space on the page is lessened.

Thanks, in advance, for any comments or suggestions. (My apologies, by the way, if this topic has been asked in the past. I did a search but didn't see it.)

 

[drawoh]

IntolerantofApathy,

When I started design and drafting, the machinists all had vertical mills with LED displays that showed inch dimensions to four decimal places. Some claimed accuracy to the four decimal places.[ ]

I was advised that bolt circles or pitch circles or whatever it is you want to call them, were a nuisance in the shop. The shops were re-calculating any dimensions that were not X/Y coordinates from a common datum. I was working on a drafting board. I had an excellent, programmable calculator for most of my drafting board time. I worked out the coordinates. X/Y coordinates also are convenient for inspectors.

Today, the machinists are programming CNC using some form of CAM software, which almost supports pitch circles. Sometimes, I find pitch circles convenient to call up.

Slide rules and vertical knobs on milling machines are prior to my working life. I would guess that machinists used machinists ink, scribes and centre punches. Pitches circles would be convenient to specify and fabricate.

I have an article online on Calculating Locational Tolerances, which covers pitch circles. Angular tolerances get out of hand very quickly. If you use pitch circles, I strongly recommend GD&T.

--
JHG

 

[drawoh]

IntolerantofApathy,

If drawings get messy, consider hole tables. SolidWorks has excellent support for these. I would assume the other CAD packages work with them too.

--
JHG

 

[pylfrm]

IntolerantofApathy,

SolidWorks has a feature called "Angular Running Dimensions" which is similar to what you describe. I realize you asked about Y14.5, but perhaps this information is better than nothing:

http://help.solidworks.com/2016/English/SolidWorks/sldworks/c_Angular_Running_Dimension.htm[/URL]]Angular running dimensions meet ISO-129-1: 2004 rules while providing additional styling options.

I'm not familiar with ISO drafting standards, so I can't verify this statement.

Although perhaps more labor intensive, you can probably achieve a similar result in many CAD packages. Hiding half of each dimension line is one possibility. Overlapping multiple dimension lines and messing with the dimension text alignment is another.

I can't say whether any of this is actually a good idea in your situation.


- pylfrm

 

[CheckerHater]

To be honest, I still don't quite understand what OP is complaining about.
What is "polar equivalent of ordinate dimensions"? There are polar dimensions and ordinate dimensions, they cannot be the same.

Perhaps, we are talking about "rectangular coordinate dimensions without dimension lines"? So the OP concern is that "polar coordinate dimensions without dimension lines" are not supported by Standard and/or CAD systems.

There is couple things to consider here. First, any kind of dimension can be converted to rectangular coordinate with any required accuracy, and/or tabulated.
Your beautiful polar dimensions will be converted to rectangular for the purpose of machining anyway.

Second, there is absolutely no need for "successive concentric arcs", because all of your dimensions can fill in just one single arc (we all know that Basic dimensions do not create tolerance accumulation).

And, as pylfrm already mentioned, SolidWorks already does it, and in today's world it is more important than those pesky standards.

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