When you think about what makes the modern world tick, you might think of electricity, cell phones, airplanes, or any number of modern conveniences. What we don’t normally think of, however, is the humble bearing that makes at least two out of three of those function.
Without bearings, the wheels on your car wouldn’t roll and the engine definitely would not work. Bearings reduce friction and keep components precisely in place. These little guys are so important that the Allies decided to strategically attack German bearing capabilities during World War II, at a very heavy loss. Hopefully the bearings in your projects will be used for more peaceful purposes.
Types of Loads
There are two main types of bearings: thrust bearings, which keep a round item spinning and in position while thrust is applied (a lazy susan, for example), and radial load bearings, which keep a spinning item in position in the radial direction (skateboard bearings, for example). A third class of bearings, the tapered roller bearings, are able to withstand force in either direction.
I suppose you could say that all three can withstand force in either direction, since a lazy susan doesn’t slide horizontally across a table and skateboard bearings don’t just slide off their axes. However, the main force resisted is decidedly in one direction.
In my experience, when bearings are mentioned most people immediately think of ball bearings. These are generally radial load bearings (skateboard), although they can be made as thrust bearings if needed. Roller bearings are more commonly used as thrust bearings, although it’s not uncommon to see them used in a radial loading application.
Types of Bearings
There are many specialized types of bearings. Here are a few you might see in your everyday life while making awesome stuff:
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“Normal” Radial Ball Bearing – What someone would normally think of as a bearing, with two concentric metal circles separated by little metal balls. These simple bearings can be found in everything from skateboards to drills.
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Pillow Block Bearing – These bearings are a radial load bearing encased in a housing that can be attached to a surface parallel to the axis of rotation.
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Cam Follower Bearing – A radial load bearing with a threaded rod attached to it. Generally meant to ride on a cam to cause linear motion, these could have other interesting applications.
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Ball Bushing (Linear) Bearing – This type of bearing is used extensively to allow for the smooth motion of 3D printer and CNC router heads. Their purpose, unlike the other bearings here, is to restrict radial motion, while allowing smooth linear motion.
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Automotive Wheel Bearing – These are generally taperer roller bearings, allowing for both radial and axial load to be overcome.
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Thrust Bearings – These have many uses (especially automotive), but lazy susans and bar stools are what immediately come to mind as easy examples of their use. They could also be useful for anything else that needs to rotate smoothly, like a camera panning device.
Alternatives
If you’re able to use bearings in your design, that is really good. However, in most applications this does take planning and extra expense. If you’re in a hurry, or are short on space, you might instead consider using a low friction material in your design. I’ve used Teflon washers successfully in a project at home. If you have access to it, there are also many low-friction coatings available.
That being said, if you can afford (both in terms of patience and money) to use bearings, it is really great to see a well engineered project that uses bearings to keep things in line and moving smoothly.
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