Simple question about symmetry positioning 2

[ApexM0Eng]

I would like to start integrating some GD&T tolerances into drawings, and I figured I would start with symmetry and true positioning
for features that I do often.

One concept I am trying to figure out is how to specify a hole should be centered within the width of a part.
Here the width is not a critical dimension, but whatever it ends up being I want the hole to be centered
with it within 5 thou of the center line.

So I mocked this up:

But from researching symmetry positioning, this doesn't seem like the proper use. What would be the right
way to specify what I wanted?

 

[drawoh]

ApexM0Eng,

I recommend you acquire a copy of ASME Y14.5-2009 and read it. I consider this particular official standard to be quite readable. Perhaps someone can recommend a good textbook on GD&T.

--
JHG

 

[KENAT]

djhurayt - a dimension doesn't need to be basic to derive a center line datum from the feature.

Take a look at the figure TWJR posted a link to.

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[Tenkan]

The centre-line shows that the holes are located half the thickness from one edge, making the .375" dimension redundant.

centerlines can be used to indicate different things; a centerplane, a linear or other pattern of holes, a hole or cylinder axis in a side view... and as far as I know they are optional to use, usually added in an attempt for clarity. Personally in this case I think the centerline is also redundant, the positional callout clearly defines the holes as a pattern on the centerplane. I don't think it could hurt to add the .375 basic dimension but I'm not certain anymore its needed at least in this example it does appear to be redundant, that is what Im wondering most.


lightweight, cheap, strong... pick 2

 

[KENAT]

The .375 dimension most definitely does hurt as it gives potentially conflicting information.

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