Can I use a flag note to define a datum target?

[cbrf23]

Hi.

I'm trying to create a drawing that is basically a work instruction for measuring a feature. The datum target is the center of a counterbore feature. I'm not allowed to put dimensions on the print because it is a work instruction that applies to multiple parts....

How can i identify the datum target feature if I can't use a dimension? My thought was to use a flagnote. Is this totally innapropriate?

Its a work instruction, not a manufacturing drawing, so I dont think violating ASME is an issue, but my own curiosity leads me to wonder how you would do this according to standards...

 

[Belanger]

Not quite sure why you want a datum "target" ... if the axis of the counterbore is to be the datum, then ASME rules would have the regular datum triangle symbol attached to the rim of the counterbore (it's then understood to really mean the axis of the c'bore). I think this is what you meant.

A datum target is a special type of datum feature where only a selected portion of a feature (surface) is used to derive the theoretical datum. If this were desired, and dimensioning not allowed, then I would add a note under the datum target balloon symbol saying "shaded area only" and then cross-hatch the desired region.

But either way, a flag note can be used if nothing else suffices.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[cbrf23]

Hi Belanger,

I took a look at the ASME book and I understand datum theory better now. (Full disclosure, I'm a designer not an engineer...but the job I'm in now has me taking on more of a role with the engineers and working with prints).

I ended up creating datum axis a on the overall length of part, b on the width of part, and c on the rim of the c'bore to create datum references.

Thank you.

 

[pmarc]

cbrf23,
Is there a chance we could see even a rough sketch of how you did it?

 

[cbrf23]

Hi pmarc. I would like to, but its a customer part and I dont want to violate our confidentiality agreement. Thats why the original image was cropped to such a small area...

What I did was dimension the overall length as 'L' and added my datum to that dimension, indicating the datum axis is to run through the center of the part. (I added a note to refer to customer drawing for dimension 'L') I did the same for the width.

I created a detail view from a cross section through the c'bore and added a datum callout to the flat of that feature.

Then I just wrote instructions like "2x 'A' from center of gage ball to Datum A" or "4x 'C' from center of gage ball to Datum B"

And lastly I have a table for the dimensions 'A', 'B', 'C', etc which are all basic dimensions.

I know without a visual its hard to say if that works or not, but I think it would meet standards.... The customer drawing has dimensions that say "'X' to datum A" and some that are to datum targets (which is why I used a datum target in the first attempt)

 

[ctopher]

My understanding is a work instruction is specific to your company, ASME standards (dims, datums, etc) do not need to apply.

If you need to show dims and datums etc, attach the drawing to the work instruction. Or, reference the dwg in a note.

Chris
SolidWorks 10 SP5.0
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