Can Flatness have an associated Basic Dimension 1

[bstanford]

Flatness controls form but not usually location or orientation.

I've got a drawing where they're using the Flatness feature control frame to locate a surface to a hole. They've made the related dimension BASIC.

Can you really do that?

 

[Burunduk]

No, but how do you know there was an intent to relate between the basic dimension and the flatness tolerance? Maybe a picture will reveal something.

 

[mfgenggear]

Flatness controls form but not usually location or orientation.

I've got a drawing where they're using the Flatness feature control frame to locate a surface to a hole. They've made the related dimension BASIC.

Can you really do that?

yes as said wrong for sure.
parallel is use with flatness.
when there are two parallel flat surfaces.
picture is worth a thousand words

 

[bstanford]

No, but how do you know there was an intent to relate between the basic dimension and the flatness tolerance? Maybe a picture will reveal something.

The drawing is proprietary. But, since there are no other feature control frames on the entire print except for the flatness callout in the same view as the BASIC dimension... I believe someone thought they could get away with it.

 

[3DDave]

The flatness geometric characteristic symbol cannot be used to control location.

 

[Garland23]

Perhaps the flatness callout is tagged to a surface that also happens to be a datum feature. Then, you could indeed locate a hole (position) from that "flatnessed" surface.

 

[mfgenggear]

Geternally holes use true position.
What makes a difference if it's a bolt hole or precision fit. And if locations are important or not.

The drawing is proprietary. But, since there are no other feature control frames on the entire print except for the flatness callout in the same view as the BASIC dimension... I believe someone thought they could get away with it.

 

[bstanford]

Here's the information I'm working with.
Never seen Flatness used this way.

 

[mfgenggear]

Here's the information I'm working with. View attachment 8030
Never seen Flatness used this way.

Untoleranced basic dimension. Drawing is un complete. There needs further constraints.
3 datums, one more dimension, and a FCF with true position. Fails to comply with ASME.

 

[Burunduk]

As noted by mfgenggear, it's clearly an incomplete drawing. Is there a chance its is completed in some other document? I'm more inclined to think that the .003 basic distance is related to a position tolerance for the hole that is not shown here, locating the hole from datum A. Somehow I doubt that someone intended it to work the other way around and to locate datum feature A from the hole... by flatness!

 

[jassco]

@bstanford:

No, that flatness feature control frame does not control location of the surface feature A. It is used to qualify datum feature A. Without it, surface feature A can be of any shapes.

 

[3DDave]

Here's the information I'm working with. View attachment 8030
Never seen Flatness used this way.

Habitually users assign datum feature symbol letters in order of application, with "A" being the first. Since the hole is identified with a datum symbol and the letter "B" it would ordinarily be referencing "A" or, if somewhat later in the alphabet, some earlier lettered datum feature.

Since none of the remainder of that image has any dimensions associated with it they may have hidden them or deleted them or just been incomplete and shipped the work as-is.

Flatness is being used as flatness should be. Everything else that provides dimensions and tolerances is missing.