Does anyone know why Hendey used a floating conical bearing at the rear of the spindle? It is a very unusual design and very expensive to build so they must have had a compelling reason. Normally a conical bearing is used to take axial thrust loads, which is what the conical front bearing does. However it would be a disaster to place a thrust bearing at the rear of the spindle as thermal growth of the spindle would unload the front bearing increasing bearing play and displacing the chuck. The text of the patent states this and states this is why the rear bearing is floating. So they created a thrust bearing which is not a thrust bearing. They had to have a reason, but it escapes me.