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Position tolerance of an axis?

Position tolerance of an axis?

Position tolerance of an axis?

(OP)
Hello all,

In your opinion can I give a position tolerance of an axis?
I have defined the axis through 3 angles and one point (defined by 3 coordinates x-y-z), since this axis refers to a complex inclined geometry. So the next step would be the definition of the position tolerance on a diameter. Unfortunately I do not have a real diameter due to the complex shape. I can find much more easily an axis.

Thank you!

RE: Position tolerance of an axis?

Does your feature pass the 'caliper test' or more correctly 'Feature of Size':

Quote (ASME Y14.5M-1994 1.3.17)

Feature of Size. One cylindrical or spherical surface, or a set of two opposed elements or opposed parallel surfaces, associated with a size dimension.

Generally tolerances are applied to features, not theoretical axis or planes etc.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Position tolerance of an axis?

Instead of axis, since it's a complicated geometry it might be better to use the "boundary" idea. In GD&T it would still be the position symbol, but the interpretation would be based on the physical boundary of the feature, not its axis.
There's also the option of using profile of a surface, which controls the location (and form) of the physical surface.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

RE: Position tolerance of an axis?

tanner78,

You can only apply position tolerances to real features (of size). Can you apply profile tolerances to faces?

--
JHG

RE: Position tolerance of an axis?

(OP)
Yes, I've already applied profile tolerances to the faces.
The overall surface is a mix of splines which lead to a sort of ovoid-shaped tube.
Profile of a surface is surely the best way, but for the measurement a kind of "reference" axis or point is needed to begin with the measurement. That's why I'm trying to use an axis.

I hope I made myself clear. Thank you very much for your replies.

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