The Debate

[operator1]

A coworker of mine and I are debating on whether or not Basic Dimensions have tolerances. We need a moderator. Anyone?

[craiger_ny]

Your tolerance is the target zone defined in the feature control frame.

[operator1]

Your tolerance is the target zone defined in the feature control frame.

.....yyyyyyeah......Let's act like I don't know what target zones are....

[rangerboat72]

Do you have pictures? LOL...

WCS...

[rangerboat72]

.....yyyyyyeah......Let's act like I don't know what target zones are....

You know what a FCF is don't you?

[cmmguy]

A coworker of mine and I are debating on whether or not Basic Dimensions have tolerances. We need a moderator. Anyone?

No, but they are sometimes reported for informational reasons

Do you have pictures? LOL...

WCS...

Yes

[rangerboat72]

Yes

You already sent them to me...

[rangerboat72]

A coworker of mine and I are debating on whether or not Basic Dimensions have tolerances. We need a moderator. Anyone?

Ok, back to the question. If the [BASIC] dimension is used to establish a datum or is used to establish a point of reference (where to take a measurement), then no it does not specifically have a tolerance.

[Wingman]

The answer is NO, there are no tolerances on Basic Dimensions. Ever. As stated here they are controlled by FCF's.

[cmmguy]

Ok, back to the question. If the [BASIC] dimension is used to establish a datum or is used to establish a point of reference (where to take a measurement), then no it does not specifically have a tolerance.

A basic never has a tolerance... it may be part of a tolerance.

And no I did not send them to you... I keep my word... sorry.

[Perry Fisher]

A coworker of mine and I are debating on whether or not Basic Dimensions have tolerances. We need a moderator. Anyone?

Your tolerance is the target zone defined in the feature control frame.

We have the same discussions with a customer who makes everything a basic dimension. Then their general tolerance is a profile callout to cover dimensions not tied to an FCF. I talked with their CMM programmer and settled on applying ±1/2 the general tolerance profile callout to the affected dimensions. Right or wrong that's what how my customer wanted them reported.

This particular customer is French owned. The prints originated over there.

To answer Op1's question a BASIC dimension should be tied to an FCF. Otherwise it should not be basic. My opinion.

[Wingman]

We have the same discussions with a customer who makes everything a basic dimension. Then their general tolerance is a profile callout to cover dimensions not tied to an FCF. I talked with their CMM programmer and settled on applying ±1/2 the general tolerance profile callout to the affected dimensions. Right or wrong that's what how my customer wanted them reported.

This particular customer is French owned. The prints originated over there.

To answer Op1's question a BASIC dimension should be tied to an FCF. Otherwise it should not be basic. My opinion.

That is legal. The profile is an FCF. The Engineering firm that I worked with called this a CYA note. LOL

[#2#]

Same as above - no tolerance it is (should be) located elsewhere.

I do however report basic dimensions but apply no tolerance. Why? It doesn't do much good to tell a machinist "This hole is out of tolerance for its location." What are they going to ask you??? "Which way and how much?" The information they need to know to adjust the machining to make it right.

[Gregl]

No tolerance & I have gotten a goverment source inspector to agree, at a prior job.

[[email protected]]

I agree, no tolerance. Basics are usually controlled by the feature control frames they are attached to often with position or profile callouts