I've now made all of the components for my engines waterpump and was going about creating the assembly as one would in the real environment. I didn't get far before I got stumped on trying to mate the main shaft inside the housing so that it would be fully defined. I just can't seem to find enough reference points that would still leave it free to spin (rotate). The main body is the fixed component, I then mated the bearing seal, and then the bearing inside the main body, all fully defined. Next, I had to insert the shaft into the graphics area and mate the impeller onto the shaft before mating the shaft to the main body. Hence, the shaft and the impeller remain undefined. I've used numerous concentric mates, parallel plane mates and tried other mates, to no avail. Where am I limiting my perspective on this? Parts are attached.