Bearings are crucial components in mechanical equipment, with precision, performance, and reliability determining the mainframe's output. The quality of bearings directly affects the efficiency and lifespan of machinery. High quality bearings reduce friction and increase equipment service life, while low quality bearings cause troubles and hinder performance. As quality standards increase, the bearing industry must continuously upgrade products and innovate technology to meet demands. However, the public generally lacks knowledge of bearings due to their status as fast-moving consumer goods. To improve understanding, we consulted with Chinese bearing experts on bearings' structure, sizes, and performance and how to judge quality bearings.
ball bearings
Check the Manufacturer's Reputation
One of the most important factors in choosing quality bearings is the reputation of the manufacturer. A reputable manufacturer will use high-quality materials and advanced production techniques to produce bearings that meet or exceed industry standards. To ensure optimal machinery performance and production safety, purchase high quality bearings from reputable sources. Choosing cheaper options may lead to machinery breakdowns and increased costs in the long run.
Bearing manufacturers that comply with industry standards and regulations typically have certifications to prove it. Look for certifications such as ISO 9001 or the European Union's CE marking. Compliance with industry standards and regulations is an indication of a manufacturer's commitment to quality.
Examine the Packaging
Bearing quality can also be judged by examining the packaging. High quality bearings are typically packaged in clean, sturdy containers that protect them from damage during transportation and storage. The packaging should also include clear labeling and instructions for use.
Check the Bearing's Finish and Texture
The finish and texture of the bearing can provide clues about its quality. High quality bearings will have a smooth, even finish, and a consistent texture. In contrast, a low-quality bearing may have rough edges, burrs, or uneven surfaces.
Rigidity is an Important Index
Rigidity refers to the power required for bearings to produce unit deformation. Rolling bearings have short elastic deformation and can be unconsidered in many types of equipment. However, in equipment such as machine tool principal axis, it is an important factor. Cylindrical and tapered roller bearings are ideal for supporting loads with rolling elements and rollaway nests.
Consider the Shaft Size When Selecting Bearings
When designing machines, it is important to consider the size of the axis first and then choose bearings accordingly. Ball bearings are suitable for small shafts, while roller bearings are ideal for large shafts. Needle roller bearings, extra-light, and ultra-light series of ball or roller bearings can be used to increase flexibility in machines with restricted diametric directions. Narrow or extra-narrow series of quality bearings with balls and rollers are ideal for machines with axial location restrictions.
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Installation and Removal Convenience is Key
When selecting quality bearings, it is crucial to consider how easy they are to install and remove. This is particularly important for large and oversize bearings. Angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, and needle roller bearings are easy to install and remove because their inner race can be set on the shaft and in the housing bore. Spherical roller bearings, double row cylindrical roller bearings, and spherical ball bearings with inner diameter tapered bore are also easy to install and remove.
Test the Bearing's Durability and Load Capacity
The load is an essential consideration when selecting bearings. Roller bearings are ideal for supporting heavy loads, while ball bearings are better suited to lighter or medium loads. Quality bearings made of carburizing steel or with Bainite quenching can support vibratory shock loads. Choosing the correct bearings based on load factors is essential for safety and durability in industrial manufacturing.
Finally, you can evaluate quality bearings by testing their durability and load capacity. You can perform tests such as the rolling contact fatigue test, the impact test, or the load capacity test to determine how well the bearings will perform under real-world conditions.
Conclusion
Choosing quality bearings for your machinery is essential for optimal performance, increased service life, and reduced maintenance costs. By considering the application requirements, shaft size, rigidity, installation and removal convenience, load factor, and purchasing high quality bearings from reputable sources, you can ensure the best performance and longevity for your equipment.
A version of this article was originally
published in Triathlete Magazine
In the April 2009 issue of Triathlete, in the Tech Support column, there was an article that mentioned ceramic (hybrid) bearings and recommended a Grade 3 bearing or better. From the Internet, I found that some manufacturers say Grade 5 bearings are the best to get (for cycling applications), while others say Grade 3 is the best. If Grade 3 bearings are the best, does that mean that the Grade 5 Ceramic bearings used in my FSA bottom bracket and HED FR wheels are no better than a steel bearing? Thank you.
Jack, Louisiana
Dear Jack,
ABEC Grade 5 bearings are actually better than Grade 3 and Grade 3 was the minimum grade recommended in the article, so the bearings you have are some of the highest grade readily available in the cycling industry. The higher the ABEC grade of a bearing, the more symmetrical and tighter the tolerances of the rings (races) that hold the balls. Bearing ratings can be confusing and they only tell part of the story, thus some additional information may help.
Bearings in the cycling industry are rated by their ABEC grade and/or by their overall roundness in millions of an inch. Cartridge bearings are the most common type of bearings on bicycles and most companies usually rate by their ABEC grade over their millions of an inch grade. For this reason, I’ll discuss ABEC ratings first.
ABEC Rating: The “Annular Bearing Manufacturers Association” has a committee that sets standards for bearing precision called the “Annular Bearing Engineers Committee” – “ABEC”.
Cartridge bearings are the most common bearing type in the cycling industry. A “cartridge bearing” means that the balls, seals, grease and the internal and external races are all built into a single cartridge bearing unit that is usually press fit into the application. ABEC grading considers the precision of the rings (races) that the bearings roll on, but not the precision of the balls. The ABEC scale rates bearing precision on four levels: 1, 3, 5 and 7.
ABEC 1 is the lowest level of bearing that is considered “Precision”. ABEC 1 bearings are specified on three variables:
ABEC 3 bearings are rated on the same three dimensions as ABEC 1, although at tighter tolerances. For example, an ABEC 1 bearing will have .0003mm of Radial Run Out (roundness variation), while an ABEC 3 has only .0002mm of variation.
ABEC 5 bearings not only have tighter tolerances on the three core variables above, but they must also adhere to set standards on additional dimensional items within the bearing as established by ABEC. These additional tolerances provide greater precision and lower rolling resistance. The differences between a Grade 3 and 5 bearing for cycling are noticeable and many companies use Grade 5 for this reason. Grade 7 bearings tighten the tolerances further still.
It is important to note that the ABEC rating system only applies to the tolerances that ABEC sets as standards and does not consider some other important variables that can affect bearing performance and durability. Ball tolerances, materials, grain structure, grease, seals and manufacturing environment are examples of things that are not taken into account by the ABEC ratings.
Millions of an Inch Rating: You may also see bearings listed anywhere from Grade 2 to Grade 1000 in the cycling industry. These parameters simply refer to how round the balls are in millions of an inch. In this rating system, the lower the number the better the quality of the bearing and the harder and better finished the bearing. For example, a Grade 25 is round to 25/1,000,000″, while a Grade 1000 is round only to 1000/1,000,000″. For perspective, loose bearings found in a Shimano Dura Ace hub, would often be Grade 25.
So, what do you need to know when you are selecting bearings for cycling?
If you are looking at loose bearings graded between 2 and 1000, get the lowest number available for the application. The price difference is minimal between a Grade 25 and a Grade 300 or 1000 and the tighter tolerances and roundness of the bearings makes a notable difference in any rolling application (like hubs).
If you are looking at ABEC graded bearings, a Grade 1 bearing does not have very tight tolerances and performance will be limited. A Grade 3 is a significant step up from Grade 1, while a Grade 5 is where the performance “sweet spot” is located for cycling. This is why most ceramic and ceramic hybrid bearings for bicycles are Grade 5. Grade 7 bearings offer only a small gain in tolerances compared to Grade 5. The cost of a Grade 7 bearing can be up to ten times the cost of a Grade 5 bearing and would really only show further benefit in very high RPM mechanical applications (well beyond what can be achieved on a bicycle).
As mentioned above, because ABEC bearing grade only reflects precision of dimensions, you need to be careful that you still get what you want in other important aspects of bearing performance. For example, ABEC ratings don’t take materials or hardness into account and thus you can have an ABEC Grade 5 steel bearing, Grade 5 Ceramic or Grade 5 “hybrid” bearing.
Full ceramic bearings use ceramic balls and ceramic rings (races). Ceramic is significantly harder than steel, requires less lubrication and is lighter, so a top quality Ceramic bearing will offer less rolling resistance, greater durability and lower weight than a steel bearing of the same grade. Hybrid bearings are the most common type of “ceramic” bearings in the cycling industry. In a “Hybrid” bearing you will find ceramic balls rolling on steel races. So, look at the big picture and realize that if you want the full benefits of a Ceramic bearing system, you need to look beyond the grade and at the materials, the quality, and the fabrication of the bearing as well.
Hopefully this helps you select the right bearing for your needs and high quality Ceramic bearing technology is well worth considering if you are trying to maximize your performance and are upgrading a high precision component.
Ride hard and smart.
Ian
Thanks to Max Ralph at FSA for helping with this article.
Originally published August 2009/ Copyright © 2009
This article has been edited to reflect more accurate information on bearing performance since its writing. Search “bearing” in our website for articles with additional and newer information.