Question on base alignment

[[Th...]]

Why can't I use the cylinder for rotation on the base alignment?

base alignment.PNG

[[Ma...]]

A cylinder is essentially a 3d line. The rotation is not being stopped by the axis of the line. Try using a circle, that will give you a point where the rotation is stopped.

[[To...]]

you could also use an Intersection Construction of the Cylinder and the Plane, which creates a point, similar to Mark's answer.

[[Th...]]

So if I go with Intersection Construction and set that as the +Y alignment, when I remeasured the cylinder, the X axis will always be off to one side or the other but never at 0. What can I do to set the cylinder as 0 on X axis?

[[Dy...]]

Draw a 3d line from the circle to cylinder then project it up to the plane and use that as your rotation?

[[Ph...]]

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Recall the feature points of the cylinder into a circle and use it as the planer rotation. This can produce same behavior that takes place within a position characteristic when cylinders that have the same normal vector are used as secondary & tertiary datum references with "ISO 5459" constraints applied.

[[To...]]

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In the Base Alignment window, change the direction to +X

[[Er...]]

In the Base Alignment choosing +X as the planar axis should work.