Guides: Bearing Basics: Parts of a Bearing Explained
Ball bearings, or fidget spinner engines, were a somewhat difficult concept for me to wrap my head around at first not coming from a background of activities where I came into contact with bearings of any sort. But if you're going to get deep into the fidget spinner industry, you're going to learn about bearings as an ancillary function. This post in our series on bearings delves into the parts of a bearing and how all of those parts fit together. So, when someone is casually explaining to you how to clean your bearing and they whip a phrase like "remove the shields" right over your head, you'll know what they mean.
Bearing shields serve as, you guessed it, a shield to the inner workings of the bearing. Your bearing might come with a shield on one side, a shield on both sides or completely open with no shields at all. The shields aren't necessary for the bearing to function but do help keep your bearing clean and free of lint and other debris that will eventually work its way into the bearing and ultimately create added friction thus slowing your bearing's spin which is something we want to avoid. They are usually easy to remove for the purposes of cleaning if they are simple rubber shields by slipping a knife or similar object underneath an edge. They flip right off and snap right back in just as easily. Some bearing come with metal shields that are not as easy to remove with damaging the outer race of the bearing.
The inner race of a bearing is essentially the inner circle structure of the bearing that the balls rotate or spin around. Inner races are usually either steel or ceramic in most fidget spinner bearings. There is a groove on the inside of the race where the balls rest. The groove is usually shaped so the ball is a slightly loose fit in the groove so there is less friction when spinning. Races come in many types of metal and ceramic materials.
The bearing balls are of course what makes the bearing spin. Bearings come with a variable number of balls in them and are usually held in between the bearing races by the bearing retainer or cage. Not all bearings have cages. If your balls are not held in place by a cage, or you wish to remove the cage, then there needs to be enough balls to fill more than half the circumference of the bearing in order for them to stay in place. Otherwise they will fall out. Bearing balls come in all sorts of exotic metals and ceramics, the most common being 52100 chrome steel.
Retainer or Cage
The bearing cage acts as a holder to separate the balls resting within the inner and outer races and in most cases holds the bearing together. Cages can also serve to lubricate the bearing by acting as a reservoir for oils, or by supplying a solid film via the cage material itself or a coating on the cage. Most of the fidget spinner bearings run dry (without lubricant), so if you want a longer spin time, we advise you use a bearing without lubrication. If your bearing comes lubricated, it's fairly easy to clean the lubricant out to achieve a longer spin.
The outer race is of course the outer ring of the bearing. Like the inner race, it also has a groove for the balls to rest in and is usually shaped so the balls fit slightly loose in the groove. This loose fit gives the balls only a single point of contact on each race reducing friction which is what we want to avoid.
For more information on bearings check out our article on which size bearing is best for fidget spinners.