Regardless of what type of item a bearing is in, its general structure is the same. There is a ball or cylinder set within a ring or a liner raceway, which allows force to be placed on the ball or cylinder (known as loading). Ball bearings usually contain multiple spherical balls that can handle both radial and thrust loads. With a roller bearing, the roller is cylindrical rather than spherical. The idea behind both types of bearings is to reduce friction and allow smooth motion.
In ball bearings, a radial load means the bearing will rotate or roll under tension, while a thrust load’s motion depends on the force and the angle. The ball bearings in a drawer slide are geared more for a downward force than a thrust force. This is why drawer slides should not be mounted flat if they are a side mount slide. The bearing in roller bearings reduces friction to allow for rotation of heavy radial loads and limited axial loads (not thrust loads).
Roller bearings are often used for heavier loads than ball bearings, and as a result, roller bearings can be found in a lot of industrial and heavy equipment like pumps, turbines, and fans. Ball bearings are more common than roller bearings, especially when it comes to items you can find around your house. Examples of such items include wheels and hard drives and, of course, one of the most popular kids' toys of the year: the fidget spinner. Some of the super heavy-duty drawer slides also have roller bearings. These are generally arranged in a "V" guide so that they have more lateral stability.
Metal vs. Plastic Roller Bearings
There are a number of different types of bearings that you can have in your drawer slides. In general, ball bearings are considered to work better than roller bearings when it comes to drawers, but this is not always the case.
Metal Bearings
Metal ball bearings are rugged, cheap and considered to be the best choice. They can carry loads over 500 lbs. that cannot be achieved with a roller slide. They can handle high velocity applications better than a roller bearing slide.
Ball bearing drawer slides are very precise; therefore, your drawer and cabinet must be precisely built. Another downside to ball bearing slides is that they need to have lubrication. The grease required with ball bearing slides will attract dust, dirt and debris which will affect the smooth action of the slide over time. Corrosion is another factor; stainless steel ball bearings are used in higher end drawer slides to resist rusting.
Plastic Roller Bearing
Plastic, generally nylon, roller bearings (Wheels) are the most affordable at the light end of weight capacity slides >100, and they do accomplish the task of getting the drawer open, but it probably won't be as quiet, they will likely have more left and right wobble and they will not last as long. They can end up breaking and needing to be replaced. However, roller bearing slides are much easier to install and are more forgiving of errors. There are also some plastic ball bearings used in aluminum slides and slides that have a powder coated finish.
Engineered Plastic Roller Bearing
Drawer slides with roller bearings that engineered for demanding applications usually have Delrin® roller bearings. Delrin® is a high density engineered plastic that is self-lubricating and negates the need for grease. This is why most all restaurant and commercial food service equipment that needs to be NSF certified will have roller slides. These slides are designed to be quickly disassembled and cleaned daily in commercial dishwasher at high temperature.
This grade of slides can also handle high loads up to 450 lbs. and are usually used in industrial applications.
Choose Wisely
When it comes to selecting the right bearings for the drawer slides on the drawers in your home, there are a number of options that work, but some choices are better than others. The ideal option for your drawers would be metal ball bearings. While other bearing types are available for drawer slides, such as plastic roller bearings, they are not as smooth or reliable as wooden and metal ball bearings.
How Ball Bearings Work in Drawer Slides