Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

[swoop360]

I need to control the shape of a hole, so naturally GD&T should be applied. Based on our requirements, we are able to accept a more oval or lobed hole, but profile irregularities need to be strictly controlled as they will affect the performance.

Since Circularity controls all 3 together, is it permissible (and best practice) to define a circularity tolerance of x and also apply a profile-of-a-line tolerance, y, to ensure a smooth profile? Where y << x.

 

[btrueblood]

Surface finish might be more appropriate to control any sharp steps, etc.

 

[swoop360]

@btrueblood, I could see how surface finish could work in a regular hole, in this case the profile that I am trying to control is a tapered hole that ends in a knife edge and the quality of the edge of the hole is critical. The surface finish leading up to the knife edge does not have a statistically significant impact on the performance.

..sorry, should have included that detail from the beginning.

 

[drawoh]

swoop360,

Profile controls circularity.

You would apply profile and circularity, because you need the circularity to be very much tighter than the profile. You wind up with a very round hole, with a diameter and location not nearly as well controlled.

I think btrueblood's suggestion is closer to what you want. I don't see anything about profile or circularity that lets you specify it over a unit of length.

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JHG