Frictionless Axis of rotation 1

Assuming you are using solid elements (blue) to mesh the model as opposed to shell elements, create a rotational constraint by first creating a cylindrical coordinate system in mechanical located at the axis of your pin hole.

Next, create a constraint, but change the coordinate system reference to the newly created cylindrical csys. You should now have new constraint options r, theta, and z. My guess is that you would pin r and z and free theta.

Good luck,

Steve

cool - worked straight off....spent a whole day yesterday trying and knew I was missing a trick....thanks.