Basic dimensioning of in-line objects

[James7443]

This is not a GD&T question, rather just basic dimensioning for clarity.

I reviewed a drawing of a plate with 4 rectangular cutouts in-line with each other. Cutouts are to reduce weight. The original drafter dimensioned edge of the first cutout only. I indicated that the dimension should have a 4x on it to indicate that the side of each the 4 cutouts are in-line (same distance from origin) or alternately put a phantom line between each of the 4 cutouts. The original drafter indicated that since they appear to be in-line it is implied that they are all at the same dimension.

Does anyone know if there is anything in the ASME specs that covers the correct way to do this? I know this is a simple question but I haven't found anything in the specs that specifically covers this.

Thanks in advance.

Ron

 

[ewh]

A similar question addressed this a few years ago... thread1103-340373

I am curious to learn of further opinions regarding this.

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

 

[KENAT]

Sure ASME Y14.5M-1994 section 2.7.3 basically says that just showing features aligned does not imply any tolerance on how aligned they are. You can find the extract on this forum with a little searching.

If you are using +- tols on the dimension you show in your sketch to control the size & location of the features then you need to invoke those tolerances (i.e. the dimensions) for each slot. So either the 4X or the phantom lines you suggest.

If you were using surface profile or position tolerance to control the slots then you could make an argument that showing them aligned is enough - as the profile/position gives the control of how far off nominally aligned. However, I'd still be inclined to at least put the common center line to make it really clear.

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[drawoh]

Ron7443,

The single dimensions without the phantom lines are ambiguous. The drawing you are showing us is simple enough that no one would be confused. If you add a lot more detail, all bets are off. In SolidWorks, I would do the "4X" so that anyone reading the drawing would know to search for four features. On a drafting board, I would be tempted to use the phantom lines.

In 3D[ ]CAD, when you use the "4X"[ ]notation, it is a good idea to go into the model and explicitly force the features to line up. In 3D[ ]CAD, if the features actually don't line up, the phantom lines will be crooked, telling you that you must fix the model and/or the drawing.

--
JHG

 

[James7443]

Thanks to everyone that answered. I was hoping that there might be a section that clearly defines this subject. I did see a section in Y14.5 that cover GD&T with type of features but noting for basic drawing practices.

I guess it will come down to best practices and clearly documenting the part so that it can be interpreted one way.

Regards,

Ron

 

[KENAT]

Ron,

Take a look at my post "Sure ASME Y14.5M-1994 section 2.7.3 basically says that just showing features aligned does not imply any tolerance on how aligned they are.".

This section does apply to you even if you aren't using pos or profile 'GD&T' controls.

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[James7443]

I don't have Y14.5M-1994 as we are currently on Y14.5-2009. However this pointed me to the section I needed. The answer is the "CONTINUOUS FEATURE" symbol or callout as stated in Y14.5-2009 para 2.7.5 and 3.3.23.

Thanks,

Ron