Please take a look at the attached print. The FCF calls out T.P. to datums A-D with B & C at MMC.

The origin(XYZ-0) for the bent tube coordinates is the intersect point of the tube and the cup surface which has no relation to the datums.

The datums as designed, do not create a three plane reference however they are the mounting points on the vehicle. Still, isn't this incorrect. Shouldn't the datums create a three plane reference?

We use to just use a sphererical tol. of .060 or .118 depending on the linier tube length to tolerance the XYZ coordinates for each point.

Can the FCF as called out be used to control the bend point tolerance for the coordinate chart on the print. Or is this an example of the incorrect use of GD&T.

I think a Surface Profile callout between Points M and N would be a more proper way of controlling the coordinates of each point.

If the FCF can be used, and is correct use of GD&T, please explain.

Thanks for your input!

Kevin Knox
Q.E. Metrology/Data Collection
C.F. Gomma USA, Inc.
643 W. E. Ellsworth St.
Columbia City, IN. 46725
(260) 248-5721/ 248-5624
Work: kknox@cfgommausa.com
Home: kknox@adamswells.com

Bend Point Tolerence controled with T.P(3).xls
(34,304 bytes)

Bent Tube Tolerence with T.P.doc
(37,376 bytes)