If I am making an object and it is non symmetrical, how can I find a pivot point in it to put the joint centre at?

For example, the picture shows a tube and a thin box, the centre of the box is not the rotation point, how do I find a specific point in the box to put the pivot point?

This happens a lot with mechanical objects I make where it is difficult to find the exact rotation centre so it would be great if anyone has a solution.

I usually set the preview style to wire frame then use one of the orthographic cameras and the joint parameter editor to position the center where I require.

Quote - I usually set the preview style to wire frame then use one of the orthographic cameras and the joint parameter editor to position the center where I require.

That is what I usually do as well, but I was hoping that there would be a better way.

Yup, thats the only way I know to do it.
It is possible to write a script to scan the geometry , get the bounding box , and find its center but just visually is usually good enough.

Quote - Yup, thats the only way I know to do it.
It is possible to write a script to scan the geometry , get the bounding box , and find its center but just visually is usually good enough.

I already have a python script that finds the centre of objects, but asymmetrical objects and ones that don`t have the pivot point in the centre are difficult to get right.