Reference Point Percentage Changes If I Change Model Length?

Hi.

I've inherited a cylinderical model, which was originally produced with an extrude-revolve.

I need a mid-plane between both ends  of the cylinder. Going back and editing the original sketch at this point would require way too much redefinition of child sketches & features, so  modifying the model  to make one of the base planes the mid-plane is not really a feasible option.

So....I created a sketch, consisting of a single line, from endface to endface of the cylinder. I then exited the sketch, and placed a reference point on that line, located at 50%. I then created a plane "parallel to a plane at a point."

Then I made my cylinder longer.

Instead of remaining at 50%, the point is now at 22.6%.

The line still extends the entire length of the cylinder, but is obviously no longer at the midpoint. I'm guessing this is not supposed to happen, no?

So, anybody got a workaround for putting a plane midway down the length of a cylinder (I am trying to avoid equations, btw.)

thanks,

john

Sw2009SP4.0

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