Polymer Roller Bearings
Radial Deep Groove Ball Bearings (also known as Conrad bearings) are some of the most commonly used ball bearings. In deep groove ball bearings, the dimensions of the raceways are almost the same as the dimensions of the balls. The grooves consist of circular arcs with a radius just a little bit larger than the ball radius. The groove depth is typically ¼ of the ball diameter. This geometry of the bearing to carry radial, axial, and combined loads. However, they are used when the primary load is going to be radial. Its ability to carry an axial load depends on how much clearance there is in the bearing after installation: if the balls are able to contact the groove at an angle, then they can support a radial load.
You can find them with either single or double rows. Double rows work well supporting moment loads that may be acting on the shaft. These bearings are usually not separable, and the raceway is continuous. They are also not self-aligning, so it is important that they be correctly aligned when they are installed. Also note that even if they are not going to be lubricated, deep groove bearings are going to need some type of seal or shield to protect them from contaminants that will compromise both their performance and life span.
More information on polymer bearings from Advanced EMC Technologies: