You wanted to know the range of jobs that you can put on a knee mill. This picture will give you an idea of how crazy you can be. This piece is 6' x 6' x 1' x 14' long. You can't readily see that the main weight is being supported by an overhead crane. Th One thing that is probably the most important thing to take into consideration, is to be aware of the total weight (and how it is supported) in regards to what the knee NUT will support. The mill in the picture is a 1970's shop mill. One day I sat a job  As for your rotab, keep it in the center of the table and you will be ok. If you planned on keeping it on one end and the mill vise on the other, personally, I wouldn't do so. You will wear the ways out.