How ball Bearing Works

 How ball Bearing Works: A Brief Guide

The first thing I'm going to do is take a cross-section and we can see some of the parts. So we've got our steel balls.

Image: Google Image

Let me just back it up a moment. Got our steel balls.

 

These are the rolling elements. We've got our separator slash retainer slash cage. We've got the inner ring. And we've got the outer ring. Inner ring, also known as inner race, an outer ring, also known as outer race.

 

We've then got a seal, and we can also change this to have a shield instead. You can see here that thew shield is metal, whereas, on the seal, it's most likely going to be rubber or Teflon.

 

We can have a look at the raceways. What I'll do is I'll remove the balls and I will remove the separator, and now we can see the raceways.

 

There are two parts to this raceway. We have the outer ring raceway

and the inner ring raceway. Now, depending on the depth of the outer ring raceway and the inner ring raceway, we'll classify the bearing as being either a deep groove or shallow groove.

 

Deep groove bearings are also known as Conrad bearings.

 

Some people will tell you that they're called that because they're concentric and radial load. It's not that at all.

 

They're named after Robert Conrad.

If we change to a shield design now, we can see we have this ring-like shape, which we can install, and then we'll push the second part in until it snaps into position.

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If we switch over to a seal design, you can see that we have a sealing surface. It's going to seal along this whole section here and there and there.

It's not very well shown on the model, but that would be the seating and sealing surface. And the same here, and it will press against the inner ring.

That is a type of seal that presses on both rings and creates more friction and thus is used for lower operating speeds. Remember the idea with the seal is that we keep the lubricant inside the bearing, and any foreign parts go, moisture, water, outside.

Shields don't do that. They will trap the lubricant inside to a certain degree, although they don't form perfect seals.

Let's have a look at the bearing now as it operates. I'm gonna remove the seal, and we'll push play, and we can see that the inner ring is rotating along with the separator and the rolling elements.

The outer ring is stationary, and normally there'll always be one ring that rotates and one stationary ring.

There'll always be a stationary ring and always one that rotates, but it may be that sometimes you have it the other way around, that the outer ring rotates and the inner ring is stationary.

I haven't seen that, but this design of bearing does exist, however, normally it is the inner ring that rotates and the stationary outer ring. The main types of lubricants used with ball bearings are oil and grease.

I'll remove the outer ring and I'll show you what happens to the grease. We can see that the balls are gonna roll along the inner ring raceway, and as they do, if the bearing is packed with grease, the balls are gonna crush the grease against the raceway.

I can't get a good the angle here, unfortunately, without removing the balls and the separator, but the balls are gonna crush the grease against the raceway, and as they do, they're gonna squeeze the oil out of the grease.

Now, the grease consists of mostly oil with a thickening agent, which is quite often soap. So as we crush the grease against the raceway, the oil is going to be liberated from the grease and we're gonna get lubrication.

The good thing about grease is that it tends to stick to where we've put it, and that means it's gonna stay within the confines of the bearing.

The downside with grease is when you heat it, the oil will be liberated from the thickening agent at a certain temperature and it will run out of the bearing. At this point, you no longer have any lubrication.

Friction will increase, the temperature will increase, wear will increase, and the bearing will seize or just fail. 

Another limiting factor with grease is that when you rotate the bearing at a very high speed, I might even be able to do that now by adjusting the speed, the forces that are applied to the grease tend to throw the grease outwards.

People call this centrifugal force, other people call it centrifugal force, depends on how you want to describe it, but in engineering we say centrifugal.

And centrifugal force is gonna throw the grease out to the side, and we're gonna end up with less lubrication on the inner parts of the bearing on the inner ring side than we will have on the outer ringside.

So both the speed and the temperature make a difference to the properties of the lubricant, so keep that in mind.

When you have a bearing that has an appearance such as this, the bearing is pre-lubricated. The lubricant is already housed within the sealed area of the bearing, and you'll be able to put that bearing straight into service.

If you're heating the bearing, just be careful that you don't heat it so much that the oil becomes liberated from the grease and begins to drip out of the bearing.

You can sometimes see this even if the bearing is sealed.

Not only that, but the seal itself will only be rated up to a certain temperature, and especially if it's a rubber seal, it will not handle high temperatures.

And the final point I wanna make here is that this type of bearing may be single row or double row. You will not see a ball bearing with more than two rows. So the ball bearing is different from a roller bearing, where you may see more than two rows.

So I hope now you understand exactly all of the components of a ball bearing and how they work together, and how the bearing works in general. Let's move on to the next section of the course now, and we're gonna talk about the second category of anti-friction bearings, and this category is roller bearings.

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