profile on trimmed edge 8

[DGN1975]

does anyone have idea or references how to profile tolerance a complex trimmed edge on say a vac formed part? I don't really see any good examples in the standard to other places. Would it make sense to just point to the trimmed edge with a 'ALL OVER' profile tolerance with a note below that states "trimmed edge". using "all around" wouldn't work to me as it is controlled only in the view its shown in and a trimmed edge would go all around in 3d.

 

[Burunduk]

Tarator,
Except for a spine (curve), I think a line is mainly meant to be part of "a combination thereof" ("thereof" refers to "theoretically exact point, axis, line, plane"). An example for a line as a component of a datum could be the line from "line in plane" or "point on line in plane" from Bill Tandler's selection of datums.

 

[3DDave]

"You can't say "no use" unless you know every single use/application in the world."

I can say "no use" when the standard does not give a use, an example use, an explanation of what it is or what it is used for.

TGC is a theoretical boundary used to establish a datum, so it cannot be a non-surface.

 

[Tarator]

Burunduk,

Thank you for the explanation.

In that 'line-in-plane' example with the wedge, I would still call it an axis, rather than a line, because it is the intersection axis of the the 2 planes (actually 3 planes: 2 wedge planes and the symmetry plane).

So to me, all datums come down to plane, axis, and point (and of course combination thereof), or even just planes since axis and point can be broken into planes.

In my opinion, the word "line" should be removed from the definition of a datum in the standard.

 

[Burunduk]

Tarator,
What about the "point on line in plane" example? Is the line there also an axis?

3D,
it was not intended to be a non-surface. It is the theoretical inverse shape of the datum feature (bent tube in this case).

 

[3DDave]

Burunduk,

Show where the term "datum line" is used in the standard.

So much hand waving and no evidence.

a line as a component of a datum could be the line from "line in plane" or "point on line in plane" from Bill Tandler's selection of datums.

That is not part of the standard. The standard does not include a reference to Tandler's post as an authority.

 

[Burunduk]

Show where the term "datum line" is used in the standard

In the definition of what a datum is.

 

[3DDave]

"Used" <> mentioned.

 

[Tarator]

Burunduk,

Tarator,
What about the "point on line in plane" example? Is the line there also an axis?

Yes, the line there is also an axis. That's my point, there is no difference. Maybe I can re-formulate the question:

Could we call "line-in-plane" "axis-in-plane", and "point-on-line-in-plane" "point-on-axis-in-plane" instead? What does the term "line" add to the definition of a datum in the standard (2009 and 2018)?

 

[Burunduk]

Tarator,
As I stated earlier:

A datum axis is the center of a TGC shape that has rotational symmetry about it. A datum line that is not an axis is a line used as a datum, but doesn't fit the above condition.

Another case that was also brought up here is the option to use a nominally (intentionally) curved "spine" as a datum.

 

[3DDave]

" A datum line that is not an axis is a line used as a datum, but doesn't fit the above condition."

I searched the standards and cannot find that definition. What paragraph is that in?

"Another case that was also brought up here is the option to use a nominally (intentionally) curved "spine" as a datum."

Latching onto vocabulary without context isn't a sign of understanding; it's just mimicry.

 

[Burunduk]

Mimicry is when you only rely on examples to duplicate for your applications. Ignoring the vocabulary being used is not a sign of understanding. It's a standard, not a picture book to teach the intellectually challenged.

 

[3DDave]

You were mimicking me, not the standard, and removing the context - I already explained yours was an incorrect interpretation of my statement. Feel free to do your own work. Mimicking my words is not a sign of understanding.


" A datum line that is not an axis is a line used as a datum, but doesn't fit the above condition."

I searched the standards and cannot find that definition. What paragraph is that in?

Answer. The. Question.

 

[3DDave]

If you don't have an answer then I am certain the concept is not supported by the standard.

I touched on no obvious difference between line and axis, except line is unsupported.

"I already did, though." page, paragraph, 2009 or 2018, seems to be missing.

 

[3DDave]

OK - line is unsupported.

 

[3DDave]

So every datum that is not an axis is, per B. a line. That is (not axis) = line?

Prove it with the relevant part of the standard.

 

[3DDave]

"a line that is not an axis" from you.

 

[3DDave]

Also, "line" is not defined by itself as a datum. Page, paragraph, 2009 or 2018, seems to be missing.

 

[3DDave]

"Line is listed as a type of datum in the datum definition in the definitions section. "

Listed <> defined.

There is no "special type" in the standard.

 

[3DDave]

It is up to a standard to provide an unambiguous definition, an explanation, and an example to ensure a uniform use and interpretation.

Failing to do all three leaves the term just a sound you make in your head.

 

[ewh]

Is this bickering really necessary?

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