Targets for non datum feature 2

[c_corn]

I have a bowl (100mm). I want to measure 8 specific points on the rim and control the profile of the circle they create. So I want to use target features but I'm only aware of using target feature for a datum and this isnt a datum. my two options I see:
1: make this feature a datum and create 8 datum targets for it
2: remove the specific target

 

[Burunduk]

Creating datum target points will not achieve controlling just those 8 points. Because, even if the "rim" will be a datum feature, the controlling tolerances that are applied to it will control the entire feature and not just those 8 points.
If from whatever reason you want only 8 points to be measured the drawing can show a regular control, but the points the measurement will be based on can be coordinated with whoever makes the measurement plan and documented there.

 

[CheckerHater]

You can specify points of interest on your drawing:

https://files.engineering.com/getfi...-7485-4e17-8819-31946f383fe2&file=Capture.PNG

Then make a note saying that points ("stations") 1, 2, 3, 4, etc. must be verified by whatever method you want to verify them.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[c_corn]

thank for the answers. thats helps.

Would those target stations also work to show which non continuous surfaces I'm referring too when I'm using a <CF> modifier?

 

[Garland23]

Burunduk and CheckerHater, tell me if my understanding is correct... The OP wanted not only the designated points, but also an imaginary curve that connects those points. I think that's why he/she is asking a follow-up question about CF.
Would it make sense to do a profile tolerance on the curve created from those designated points? Or would a profile tolerance really only control the designated points? (Maybe there's no difference because any imaginary connection of those points would be perfect anyhow.)

 

[Burunduk]

By default, with or without the CF symbol on an interrupted surface and with or without the "stations", the tolerance applies to the entire feature or interrupted feature (if the CF symbol is not used for an interrupted surface, only the portion where the callout is shown is considered as the feature). If you want the tolerance to apply only to designated portions of the feature, the standardized way to do so is to indicate local segments by chain lines, with appropriate dimensions for length and location of these segments, applied to the chain lines. In the ASME Y14.5 standard, look up "Limited Length or Area Indication".

 

[3DDave]

For certain, by default, many CMM operators would not touch that many points, but a more motivated one might.

If it's necessary to specify specific points then one could identify and dimension those points on the drawing and add a note. The standard does cover a majority of typical uses, and this is not typical. However it does allow for anyone to add their own notes to cover whatever special case they want.

If they are points they wouldn't be a continuous feature. It might be (under Y14.5) be considered an irregular feature of size.

As is usual the correct answer depends on how the information will be used. Without knowing that one might as well ask for winning lottery numbers.

 

[Burunduk]

For certain, by default, many CMM operators would not touch that many points, but a more motivated one might.

Maybe "many" CMM operators will not touch that "many" points, but the majority may.
It depends on the amount of tolerance, the type of geometric characteristic or size being evaluated, and obviously the size of the feature. 8 points on a 100 mm diameter is not a lot. It could easily be double.

Nevertheless, if the OP wants to designate discrete points for inspection and exclude the rest, it is possible, but not standardized. If the Continuous Feature symbol is considered, it would make more sense to apply the concept of "limited length or area indication" to define segments of the interrupted feature, that have to fit to mutually aligned tolerance zones of nonzero length.

 

[3DDave]

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