A form of roller bearing, which uses ball bearings supported between a toroidal cup and an opposing conical surface. For maximum efficiency the surface radius of the cone and cup should match the radius of the bearing as much as possible.

The mechanism is used in wheel bearings where the wheel rests on the axle supported by pairs of cup and cone bearings.

Figure 1. - Cup/cone bearing in cross section

                  \  cup   /
          cone|\( )\______/( )/|
______________| \____________/ |______
______________   ____________   ______
              | /   ______   \ |
              |/( )/      \( )\|

The system is not very tolerant of lateral loads and works best when all loads are perpendicular to the axle

Cartridge bearings or needle bearings are better for supporting systems with both perdicular and lateral loads

The advantage of the system is that it is completely field serviceable, and even manufacturable from raw materials given the right tools (lathe, grinding powder). For example, it is possible for a boat engineer to manufacture new bearing surfaces while at sea if neccessary while cartridge bearings have to be replaced by an equivalent part.