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General Q&A
1.What are the different parts of a bearing?
The parts to a bearing are, the outer ring, the inner ring, the cage which holds the balls and the shield if it is a shielded bearing.
2.What are the most common bearing types?
There are many types of bearings, with these being the most common.
1 Open - the cheapest and most plentiful on the market
2 Metal Shielded - has a metal shield to keep debris out
3 Rubber Sealed - has a rubber shield to keep debris out
They have no shields or seals to keep debris out and lubricant in. They spin more freely when they are clean, but as they get dirty, performance suffers.
4.What is a Metal Shielded Bearing?
These have a metal shield attached to the outside ring which does not rub the outer race or the balls. They spin more freely than rubber sealed bearings and offer a good balance between maintenance and performance.
A rubber seal touches the inner and outer race and the balls as well on some bearings. Best seal, but slowest.
6.What is the difference between 2RS & 2RZ seals
7.How important are seals to bearing performance?
Seals are vital to the performance of any bearing. Replace worn or damaged seals; they allow contaminants such as dirt and water to enter the bearing and also allow lubrication to escape. In most cases, it is a good practice to replace all seals with new ones during teardown. A film of lubricant should be applied to the seal lip contact surface at assembly. This will help prevent seal damage during installation and at initial start-up. It also will reduce rolling torque.
8.What is the purpose of bearing lubrication?
● Extends fatigue life of the bearing by reducing wear and friction between the mating components of the bearing assembly.
● Prevents corrosion and extend shelf life.
● Provides a level of protection from foreign material entering the rolling elements.
● Reduces the noise level of the bearing, lowers torque, and assists the bearing in reaching maximum operating speed.
9.How much grease is too much?
For general applications a grease fill of 25% of the free space in the bearing seems to be accepted as standard by most manufacturers. Slow speed applications in harsh environments (such as agricultural machinery) can sometimes require a larger fill. High-speed applications (i.e. hand tools) can require a lesser fill. Check with HCH technical support for any special requirements.
10.What type of damage will occur when there is inadequate lubrication?
Four common bearing damages will occur when there's poor or inadequate lubrication:
a) Roller end scoring-Metal-to-metal contact from breakdown of lubricant film.
b) Cone large rib face deformation-Metal flow from excessive heat generation.
c) Total bearing lock up-Rollers skew, slide sideways and lock-up the bearing.
d) Cone large rib face scoring- "Welding"and heat damage from metal-to-metal contact.
11.What are ABEC and ISO standards?
The Annular Bearing Engineers Committee (ABEC) of the American Bearing Manufacturers Association (ABMA) establishes standards for manufacturing precision ball bearings. These standards are also accepted by (ANSI) American Standardization Institute and by international agreement for the standards developed by the International Standards Organization (ISO). The ABEC and ISO bearing standards primarily define tolerances for the ball bearing rings.
12.Is it safe to randomly select a bearing clearance?
Selection of the proper initial bearing internal clearance must take all the foregoing factors into consideration. Assuming this has been done, it is never advisable to replace a bearing with one having a lower initial clearance. By the same argument, it is usually safe to substitute a larger clearance when the desired clearance is not available. Therefore,standard clearance and C3 clearance is suggested in usual applications.
13.Does internal clearance affect the bearing precision?
Internal clearance is the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the HCH suffixes: C2, C3, C4 and C5, where no suffix indicates normal clearance. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4.
Precision is a range of tolerance on bearing dimensions. ISO/DIN and ABMA govern the precision ranges. ISO/DIN uses Class 0 (P0), Class 6(P6), Class 5(P6), Class 4(P4), and Class 2(P2) and ABMA uses ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively the systems are generally interchangeable.
Ultimately, clearance does not affect tolerance and tolerance does not affect clearance.
14. What is the purpose of bearing lubrication?
Extends fatigue life of the bearing by reducing wear and friction between the mating components of the bearing assembly.
Prevents corrosion and extends shelf life.
Provides a level of protection from foreign material entering the rolling elements. Reduces the noise level of the bearing, lowers torque, and assists the bearing in reaching maximum operating speed.
15.What are the purpose of the seals on bearings?
There are two purposes, to keep debris out and lubricant in. The different seal types trade sealing ability for performance. The rubber seal, for example, is the slowest bearing because the rubber is in contact with the rotating bearing surfaces. The open is the fastest because it has no seals to drag. But once an Open bearing gets dirty, its performance will decrease greatly.
16.What is the performance difference in the 3 common bearing types?
There is quite a bit of performance difference in the 3 most common bearing types as shown in the chart below. This chart assumes that all the bearings are clean. So if you take your Open bearings and let them get dirty, then you lose all of the performance benefit of running them in the first place.
17.What factors should be considered when choosing a bearing?
All application data (loads, speeds, orientation, etc.), intended use, and environment.
The parts to a bearing are, the outer ring, the inner ring, the cage which holds the balls and the shield if it is a shielded bearing.
2.What are the most common bearing types?
There are many types of bearings, with these being the most common.
1 Open - the cheapest and most plentiful on the market
2 Metal Shielded - has a metal shield to keep debris out
3 Rubber Sealed - has a rubber shield to keep debris out
3. how are Open Bearings made?
They have no shields or seals to keep debris out and lubricant in. They spin more freely when they are clean, but as they get dirty, performance suffers.
4.What is a Metal Shielded Bearing?
These have a metal shield attached to the outside ring which does not rub the outer race or the balls. They spin more freely than rubber sealed bearings and offer a good balance between maintenance and performance.
A rubber seal touches the inner and outer race and the balls as well on some bearings. Best seal, but slowest.
6.What is the difference between 2RS & 2RZ seals
| Characteristics | RZ type | RS type |
| Structure | Non-contact | Contact |
| Torque | Low | Rather High |
| Dust Proofing | Better than ZZ type | Excellent |
| Water Proofing | Better than ZZ type | Very Good |
| High Speed | Very good (Same as open type) | Limited by contact seals |
7.How important are seals to bearing performance?
Seals are vital to the performance of any bearing. Replace worn or damaged seals; they allow contaminants such as dirt and water to enter the bearing and also allow lubrication to escape. In most cases, it is a good practice to replace all seals with new ones during teardown. A film of lubricant should be applied to the seal lip contact surface at assembly. This will help prevent seal damage during installation and at initial start-up. It also will reduce rolling torque.
8.What is the purpose of bearing lubrication?
● Extends fatigue life of the bearing by reducing wear and friction between the mating components of the bearing assembly.
● Prevents corrosion and extend shelf life.
● Provides a level of protection from foreign material entering the rolling elements.
● Reduces the noise level of the bearing, lowers torque, and assists the bearing in reaching maximum operating speed.
9.How much grease is too much?
For general applications a grease fill of 25% of the free space in the bearing seems to be accepted as standard by most manufacturers. Slow speed applications in harsh environments (such as agricultural machinery) can sometimes require a larger fill. High-speed applications (i.e. hand tools) can require a lesser fill. Check with HCH technical support for any special requirements.
10.What type of damage will occur when there is inadequate lubrication?
Four common bearing damages will occur when there's poor or inadequate lubrication:
a) Roller end scoring-Metal-to-metal contact from breakdown of lubricant film.
b) Cone large rib face deformation-Metal flow from excessive heat generation.
c) Total bearing lock up-Rollers skew, slide sideways and lock-up the bearing.
d) Cone large rib face scoring- "Welding"and heat damage from metal-to-metal contact.
11.What are ABEC and ISO standards?
The Annular Bearing Engineers Committee (ABEC) of the American Bearing Manufacturers Association (ABMA) establishes standards for manufacturing precision ball bearings. These standards are also accepted by (ANSI) American Standardization Institute and by international agreement for the standards developed by the International Standards Organization (ISO). The ABEC and ISO bearing standards primarily define tolerances for the ball bearing rings.
12.Is it safe to randomly select a bearing clearance?
Selection of the proper initial bearing internal clearance must take all the foregoing factors into consideration. Assuming this has been done, it is never advisable to replace a bearing with one having a lower initial clearance. By the same argument, it is usually safe to substitute a larger clearance when the desired clearance is not available. Therefore,standard clearance and C3 clearance is suggested in usual applications.
13.Does internal clearance affect the bearing precision?
Internal clearance is the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the HCH suffixes: C2, C3, C4 and C5, where no suffix indicates normal clearance. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4.
Precision is a range of tolerance on bearing dimensions. ISO/DIN and ABMA govern the precision ranges. ISO/DIN uses Class 0 (P0), Class 6(P6), Class 5(P6), Class 4(P4), and Class 2(P2) and ABMA uses ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively the systems are generally interchangeable.
Ultimately, clearance does not affect tolerance and tolerance does not affect clearance.
14. What is the purpose of bearing lubrication?
Extends fatigue life of the bearing by reducing wear and friction between the mating components of the bearing assembly.
Prevents corrosion and extends shelf life.
Provides a level of protection from foreign material entering the rolling elements. Reduces the noise level of the bearing, lowers torque, and assists the bearing in reaching maximum operating speed.
15.What are the purpose of the seals on bearings?
There are two purposes, to keep debris out and lubricant in. The different seal types trade sealing ability for performance. The rubber seal, for example, is the slowest bearing because the rubber is in contact with the rotating bearing surfaces. The open is the fastest because it has no seals to drag. But once an Open bearing gets dirty, its performance will decrease greatly.
16.What is the performance difference in the 3 common bearing types?
There is quite a bit of performance difference in the 3 most common bearing types as shown in the chart below. This chart assumes that all the bearings are clean. So if you take your Open bearings and let them get dirty, then you lose all of the performance benefit of running them in the first place.
| Bearing Type | Maintenance | Spinning Performance |
| Open | 0 | 10 |
| Metal | 5 | 7 |
| Rubber | 10 | 0 |
| Legend: 0 = Worst, 10 = Best |
17.What factors should be considered when choosing a bearing?
All application data (loads, speeds, orientation, etc.), intended use, and environment.
