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Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

(OP)
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.

RE: Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

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

RE: Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

(OP)
@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.

RE: Circularity Tolerance--Controlling Ovality, Lobing and Irregularities Independently

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.

--
JHG

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