Unilateral Angularity?

[DonIreland]

Is it possible to have a unilateral angularity callout?

I am updating a drawing to relocate Datum C from an undimensioned datum target located an uncontrolled edge of a plastic part. (Believe it or not - it has been in production this way for years and every layout ahs come back "good".....)

There is a bushing that mounts my part in application that would make an excellent "C". It is allowed to be 20° +0° /-1° from vertical portion of a centerline of cylindrical feature that identified as "B". (Datum B is already defined as axis perpendicular to "A" surface.)

Is there such a thing as a unilateral angularity callout or do I need to figure out how to do something different? I didn't think a profile callout was appropriate either and I didn't want to change nominal dimension and switch to bilateral tolerance of 0.5 degrees.

 

[KENAT]

Not sure I follow you but you can use profile in place of angularity generally speaking. As you can apply profile non symmetric does this get what you need?

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[ewh]

Profile won't get you quite the same result as angularity. Depending on part size, the area furthest from the apex will be much more tightly controlled with profile, while the area nearest the apex will be much looser.
Why didn't you want to change the dimension tolerance to be equally bilateral?

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[KENAT]

Hang on, are we talking Angularity as in section 6.6.2 of ASME Y14.5M-1994?

Surface profile is almost the same thing but with wider applicability.

If you are comparing to angular tolerance, then yes they aren't the same thing.

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[pmarc]

I think Kenat is right. OP is asking about angularity not angular direct dimension which indeed creates tighter tolerance zone close to the apex.

Profile tolerance is the most powerful geometric control of all and it can be used as angularity control as well. Generally it is also the only control that gives a possibility of assigning unilateral tolerance zones. So my in opinion profile could somehow work in this case, however I agree it is not so popular way of using it.

 

[ewh]

You are right as usual Ken. The only excuse I can claim is a brain fart, confusing angularity with angular tolerance.

I guess on the bright side, it could show that I was too preoccupied with work tasks to think my answer through properly. Yeah... that's the ticket!

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]