Last Updated on April 10, by Chen
Hangzhou Journal Bearing are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.
Choosing between a journal bearing and roller bearing can be challenging. As mechanical engineers and designers with expertise in bearings, we know that the decision should not be taken lightly. The two options have distinct differences which must be considered before making an informed choice. In this article, we’ll break down the distinctions between these two types of bearings to help you decide which one is right for your project.
Journal bearings are comprised of a shaft rotating inside a housing or sleeve. This type of bearing does not use rolling elements like balls or rollers; instead, it works by rubbing against the inner surface of the housing. There are advantages to using this kind of simple design as well as challenges to consider when deciding whether it’s suitable for your application.
On the other hand, roller bearings make use of cylindrical rollers held together by spacers or cages in order to reduce friction and increase load capacity over journal bearing designs. These components provide superior performance characteristics but also come at a cost which needs to be weighed when choosing between them both.
We hope that after reading this article, you will have enough information to make an educated decision on whether a journal bearing or roller bearing is best suited for your specific application requirements.
Journal bearings offer a variety of advantages when compared to roller bearings. The first advantage is that they have high load capacity and can handle heavier loads without compromising performance, making them ideal for applications where other bearing types may fail due to their limited load capacities. Additionally, journal bearings are able to operate at higher rpm limits than roller bearings, allowing them to be used in more demanding applications. Finally, the selection criteria for journal bearings also tend to be simpler since they come in fewer shapes and sizes when compared with other types of bearings. This makes them easier to find the right size for any purpose. In terms of bearing selection criteria, journal bearings often prove superior in terms of both load capacity and rpm limits. Moving on from this section about the advantages of journal bearings, let’s now take a look at some disadvantages which could make it harder for you to decide if these are the best choice for your application needs.
Journal bearings are a veritable nightmare for mechanical engineers and designers. They can be an absolute catastrophe in terms of design, installation, noise, lubrication and cost. Here’s the lowdown on journal bearing disadvantages:
All in all, when considering whether or not journal bearings are worth pursuing for a given application one must weigh up the pros and cons carefully before making any decisions; however they remain popular solutions among many industries despite their drawbacks thanks largely in part to their versatility and relatively simple design components.
Roller bearings provide numerous advantages compared to traditional journal bearings, making them the preferred choice for many applications. They offer superior load-bearing capacity, higher speed capability and lower maintenance requirements than their counterparts. Additionally, roller bearings are more resistant to environmental conditions such as dust or temperature changes.
The above table illustrates the primary benefits of using a roller bearing over a journal bearing. When looking at longevity, roller bearings have far greater life expectancy; they also possess much higher load capacities while remaining capable of operating at high speeds with minimal maintenance needs. Furthermore, they are highly resilient against environmental factors like dust and temperature fluctuations which can cause significant damage to journal bearings in certain circumstances.
Overall, when choosing between journal and roller bearings it is important to consider all aspects of performance including durability, load capacity, high-speed capability and low-maintenance requirement along with any potential environmental influences that may arise in the application environment. These advantages make roller bearings an attractive option for most equipment designs where long service life and reliable operation are essential criteria for success.
The disadvantages of roller bearings can be likened to an unwelcome guest. They silently lurk in the background and make their presence known at the most inconvenient times – usually when you least expect it.
To begin, they are generally noisier than journal bearings. This is due to the higher friction between moving components that come with using roller bearing designs. Additionally, wear on these parts occurs more quickly over time due to this increased friction which leads to:
Finally, as a result of all these factors, choosing roller bearings should not be done lightly but rather after careful consideration of your specific application needs. Choosing the wrong type of bearing could lead to costly repairs in addition to downtime that may have been avoided had the right choice been selected from the start. The next section will discuss some important factors one must consider when selecting either a roller or journal bearing for any given project.
When choosing between a journal bearing and roller bearing, there are several factors to consider. Bearing type is the first factor that needs to be taken into account. Depending on the application, one type of bearing will work better than another. Load capacity should also be considered – both bearings have their own limits in terms of how much load they can handle before suffering mechanical failure or damage. Speed limits must also be assessed; any excessive speed may cause premature wear on certain components inside the bearing assembly. Temperature range is important too; some materials used for these types of bearings cannot operate within certain temperature ranges without being damaged over time. And finally, installation space should be examined as well – if the working area is cramped, this could restrict your choice of bearing size and design.
Overall, when selecting between journal and roller bearings, it’s best to assess each machine’s specific requirements related to the mentioned criteria so you can choose the right bearing for its intended purpose. Understanding all of these elements helps ensure that your selected bearing will function adequately throughout its entire lifespan with minimal maintenance required.
When choosing between a journal bearing and roller bearing, it is important to consider the load-bearing capacity of each. The following table provides an overview of key differences in load-bearing capacity:
Journal bearings are generally used for lighter loads that don’t require as much strength or weight support. Roller bearings, however, can handle heavier applications with larger amounts of weight and force. Depending on the size and type, some roller bearings have higher load capacities than others. Thus, depending on your application requirements, you may need to choose specific types of roller or journal bearings accordingly. Additionally, factors like ambient temperature, speed limits, and rotational speeds must be taken into account when making a decision about which type of bearing should be chosen.
Designing machines and equipment to accommodate rotating components often means selecting the correct bearing for the job. The choice between journal bearings or roller bearings can be made based on speed, load capacity, and operating temperature. Speed and RPM limits need to be taken into account when choosing a bearing type as well.
Journal bearings are generally recommended in applications that require low-speed rotations while still maintaining high torque ratings. These types of bearings have an unlimited maximum rpm limit but tend to work best in slower moving machinery with higher loads. On the other hand, roller bearings have a much lower torque rating, but they allow for greater speeds than journal bearings due to their ability to handle more rapid rotational movements without causing excessive wear on the bearing surfaces. Roller bearings typically have a maximum rpm limitation that should not be exceeded if extended life is desired from the product.
When considering both journal and roller bearing options, it’s important to consider machine-speed, maximum-rpm, rotational-speed, torque-rating, and expected bearing-life before making your selection. Factors such as these will help you determine which option is best suited for your particular application needs. Ultimately this decision will impact how successful your project is over time so take care when researching what solution works best for you!
Now that we have discussed the speed and RPM limits, let’s move on to operating temperature considerations when choosing between a journal bearing and a roller bearing. Temperature plays an important role in determining which type of bearing is best for your application. Bearing temperature must be kept within certain ranges as high temperatures can degrade performance or cause premature failure.
When selecting bearings, it is important to know the maximum-operating temperature rating of the bearings being considered. This information can usually be found in manufacturer product data sheets or catalogs. If this information is not available, you should contact the manufacturer directly. The manufacturer will also be able to provide specific temperature ratings based on their own testing results for each model they offer under different loading conditions. Generally, journal bearings can handle higher temperatures than roller bearings due to their larger surface area and better heat dissipation capabilities; however, this varies depending on lubrication requirements and other factors such as bearing size and material used.
It is also important to consider how the temperature range of the environment may affect bearing performance over time. You should make sure that any chosen bearing has enough margin in its rated temperature capacity versus expected operating temperatures for your application so that it does not reach its upper limit during normal operation or peak usage periods. Additionally, if extreme variations in environmental temperatures are anticipated (such as rapid changes from hot to cold), then more robust materials like stainless steel might need to be specified instead of softer metals like brass or aluminum alloys.
By understanding both speed/RPM limits and operating temperature requirements ahead of time, one can choose the right type of bearing with confidence knowing that it will perform optimally while meeting required specifications without exceeding its temperature rating limits. Therefore proper selection criteria upfront helps ensure optimum system performance throughout its lifetime with minimal maintenance requirements going forward.
When it comes to maintenance requirements, journal bearings and roller bearings differ significantly. Journal bearings require regular lubrication of the bearing surfaces and must be inspected regularly for signs of wear or damage. Roller bearings on the other hand typically need only periodic inspections since they are sealed units with their own lubricant supply that is usually sufficient throughout its service life. Additionally, installation of a journal bearing requires more attention than a roller bearing; alignment between components needs to be precise in order to ensure proper operation.
Conversely, installing a roller bearing is generally simpler because they are designed as self-aligning units. Bearing cleaning also differs; journal bearings often have crevices which can trap contaminants like dirt and dust particles, so thorough cleaning should be part of your maintenance routine when using this type of bearing. With roller bearings however, contaminant accumulation tends to be less of an issue due to the seals protecting the internal components from environmental conditions.
Considering these differences in terms of required care, one must weigh all factors before deciding whether a journal or roller bearing is suitable for their application. Size and installation space may further influence this decision…
When considering the maintenance requirements for a bearing, size and installation space are also key factors. Bearing size is affected by both the journal size and roller size, depending on which type of bearing you’ve chosen. For journal bearings, their longevity can be impacted if they aren’t sized correctly. Meanwhile, roller bearings require careful consideration when it comes to proper sizing for their axial or radial loads in order to prevent premature wear or failure.
The amount of space available in an application must also be taken into account when selecting a bearing. This will determine whether there is enough room to install the required bearing without issue. If not, then alternate solutions such as using split bearings may need to be considered instead.
In addition, considerations should be made regarding how easy it will be to perform regular inspections and lubrication with regards to any maintenance that needs doing on a particular bearing over its lifetime – especially where access is restricted due to tight spaces around the bearing installation area. Properly assessing all these factors prior to making your selection will help ensure that your choice of bearing meets all necessary requirements. With this information in hand, cost and availability can now come into play when deciding upon the ideal solution for a given application.
When it comes to making a decision between journal bearing and roller bearing, cost and availability are two of the most important factors. In one fell swoop, you can go from having an amazing project in your hands to being left with nothing but disappointment due to budget constraints or lack of stock availability – so let’s look at how these bearings compare on those fronts:
Overall then, there’s no clear winner across all categories when it comes to cost and availability – however knowing what your particular requirements are should help guide you toward selecting the right bearing for your job. With that in mind, we move on to looking at environmental conditions…
When considering a journal bearing versus roller bearing, environmental conditions are an important factor to consider. Many of these applications require long-term reliability and robust operation in extreme temperatures, humidity levels and vibration exposures. To ensure the correct application is chosen for each specific environment, it’s vital to assess the requirements against both types of bearings.
These features allow us to compare different materials and decide which one best meets our needs based on the environmental conditions we must operate within, ensuring reliable operation and minimizing downtime caused by component failure due to incorrect selection criteria being applied initially.
When it comes to choosing between journal bearings and roller bearings, quality assurance standards are an essential factor for consideration. Ensuring the necessary bearing performance requires a comprehensive approach to bearing quality assurance that covers all aspects of design, production, and operation. Bearing testing standards must be established at each stage which includes manufacturing, installation, operation, and maintenance in order to guarantee proper function.
Manufacturers should adhere to strict bearing manufacturing standards such as those outlined by leading industry organizations like ISO, ANSI/ABMA, or AGMA. This includes standardizing parts materials with clear specifications regarding hardness measurements and other characteristics related to strength and durability. All components must meet specific dimensional tolerances set by these guidelines and accepted practices before any assembly can begin.
Furthermore, the quality control process must involve thorough inspection throughout every step of the manufacturing process – from raw material selection through finished product delivery – using advanced visual assessment technologies such as optical microscopes or computed tomography scans (CT scans). The end goal is obviously to ensure that only high-quality products make their way into circulation but also have them live up to their designed purpose when put in use.
Once assembled correctly according to the highest possible quality assurance standards, one may confidently choose either journal or roller bearing depending on the requirements at hand. As we move forward into the next section about design considerations, it’s important that manufacturers understand how various factors influence optimal functioning so they can make informed decisions about what type of bearing best suits their needs.
When it comes to choosing between a journal bearing and a roller bearing, there are several design considerations that must be taken into account. Firstly, the installation requirements of each type of bearing can vary significantly. Generally speaking, journal bearings require more sophisticated installation techniques than roller bearings do. Secondly, lubrication is an important factor when selecting a bearing as different types require various amounts and types of lubricants in order to function correctly. Thirdly, load capacity is another key consideration; typically roller bearings have higher load capabilities compared to journal bearings. Finally, temperature limits should also be considered—roller bearings tend to operate better at higher temperatures when compared with journal bearings.
In terms of design considerations for selecting a bearing, proper installation technique is critical for ensuring optimal performance and longevity from the part. Furthermore, understanding the materials and lubrication requirements is necessary for achieving reliable operation over time. With regard to load capacities and temperature limits, it’s essential to consider these factors according to the specific application before making a selection. Ultimately, careful evaluation of these different elements will help ensure that you select the best possible solution for your needs.
In conclusion, when it comes to choosing between a journal bearing or roller bearing for your application, there are many factors to consider. Firstly, the cost and availability of each type must be taken into account as well as any environmental conditions they may encounter in their expected environment. Quality assurance standards should also be considered so that you can rest assured that whichever one you choose will have been produced with precision. Lastly, design considerations such as load capacity and speed requirements should be evaluated in order to make an informed decision about which type of bearing is best suited for your needs. By carefully weighing all these aspects we can ensure our projects run smoothly like clockwork – providing us peace of mind that our applications will deliver optimal results efficiently and safely.
The formal technical definition of a bearing is a machine element that:
A simpler definition can be found in the name “bearing” itself: a supporting structure designed to “bear” stress or load within a given design.
While the prototypical use case for bearings is an axle rotating in a shaft, they can be engineered to facilitate many different desired ranges of motion. Linear bearings, for instance (see below), allow for linear rather than rotational motion, with the bearing element moving along a rail or rod.
The actual design of the part performing this function can vary widely. Suitable materials for bearings include everything from wood to brass to advanced polymers. Some bearing designs rely on frequent lubrication, while others operate in environments where they can almost never be lubricated (like space). Corrosion-resistant bearings are designed to resist degradation while remaining submerged for long periods of time, while high-temperature bearings need to operate under the extreme conditions of steel manufacturing plants.
Today, bearings are highly engineered components built for highly specific applications, environmental hazards, maintenance requirements, and price-points.
In the prototypical case of a rotational bearing, the “journal” is the part of the shaft which contacts the bearing surface. In the simplest possible case, a bearing is not a discrete device: the journal simply slides over the bearing surface, enduring any friction, heat, and wear generated. While usable in less demanding contexts, bearing designs that do little to reduce friction will create unacceptable magnitudes of heat and wear when used at the speeds and conditions required by demanding modern applications in fields like industrial manufacturing, aerospace, and automotive.
A huge imperative in bearing design, therefore, is reducing friction to improve the bearing’s performance characteristics and lifespan.
Several additional features can be added to reduce friction, first lubrication. Traditionally, this was done by the initial and periodic injection of grease or oil. Today, some self-lubricating bearings embed advanced lubricants into the bearing materials themselves (see Self-Lubricating Bearings, below) reducing manual lubrication needs. Other designs utilize low-friction materials that don’t require lubrication at all under the right operating conditions.
A second option is the addition of a rolling design element to reduce friction while preserving desired load-bearing characteristics. Bearing designs can be usefully divided into two high-level categories based on this addition.
You will notice that many industry sources refer to sleeve/journal bearings as “plain” rather than “plane,” as we refer to them at TriStar.
We think this distinction helps highlight the fact “plain” bearings are by no means relegated to simple or low-load bearing applications.
The “Plane bearing” term focuses on the geometric properties of the bearings rather than the mechanical complexity of the underlying mechanism. Low-friction, self-lubricating plastics mean that the presence of rolling elements is no longer a hard-guide to a bearing’s potential applications.
You can think of a plane bearing as a bearing in its simplest form: any non-rolling element that is incorporated where two surfaces rub together is a plane bearing. Common types of bearings include sleeve bearings and flange bearings (see below for more on both).
“Journal Bearing,” “Sleeve Bearing,” and “Bushing” are all roughly equivalent terms that are used by different industries to describe the same basic bearing design concept.
A sleeve bearing is the simplest design of plane bearing, consisting of a smooth sleeve that is fitted between an axle and bore. Typically, some sort of liquid or particulate lubricant will sit between the journal and axle.
A “bushing” is a closely related classification that can sometimes risk introducing confusion.
The formal definition of a bushing is a thin sleeve or tube which constrains relative motion. But how is this different from a sleeve bearing? It isn’t, necessarily. Some industries simply use the term “bushing” as a quirk of history. In general, we find that a bushing will always refer to a single-component sleeve.
Sleeve bearings are a versatile component employed in just about every sort of design imaginable. Just a few examples include:
This design adds a “flange,” or protruding rim, as a locating mechanism which holds the attached sleeve in place. This flange is attached to a mounting surface that runs perpendicular to the bearing shaft. This additional support is critical in applications with high speeds, heavy loads, or extensive vibration/movement.
In its simplest form, you can think of a thrust bearing as simply a washer. Formally, a thrust bearing provides a bearing for forces that act axially to the shaft. A prototypical example is a propeller shaft on aircraft.
Like other bearing types, thrust bearings can employ a rolling element, with balls or rollers supported inside a ring. Low-friction plastics offer analogous benefits to those they offer in linear or rotational applications: the right materials can withstand axial force with reduced need for lubrication.
A linear-motion bearing (sometimes called a “linear slide”) provides free motion along a defined path.
This linear motion contrasts with the rotational motion of the prototypical bearing design described earlier in the article. Like a rotational bearing, a linear bearing can be extremely simple--like a wooden desk drawer resting on a wooden slide track. But more complex linear bearing designs allow for less friction, faster motion, and more precise control over range-of-motion.
Examples of linear bearings include everything from desk-drawer slides to seismic shock absorbers that help protect buildings from earthquakes.
For more information, please visit Industrial Combined Journal Bearings.
In the most common arrangement, a bearing travels along a square rail- or round rod- guide.
A rail provides a track which a linear bearing moves along. The shape and design of this rail may vary depending on how loads will be borne in the intended application. As with, for instance, a curving train track, this rail does not need to be in a straight line.
The rail-mounted bearing mechanism is known as a “carriage” or “block.” The point of contact between the carriage and the rail is known as the “race.”
As with a rotational bearing, friction is generated between these two parts. This friction can either be dissipated with some combination rolling elements, lubrication, and low friction/self-lubricating plastic sleeves.
In general, all the bearing design elements we explore in this article apply to linear bearings as well, including seals, lubrication, and self-lubrication options.
For instance, an oil-infused bronze sleeve is one common low-load design; a simple example is a slide-out track for a drawer. More demanding applications begin necessitating more complex mechanisms. Some linear bearing designs even incorporate a wiper mechanism in front of the bearing to clear dirt and debris from the rail and limit contamination.
Linear bearing applications are as broad as those of rotational bearings. They range from simple furniture drawers up to rollercoasters and high-performance machine tools that require extremely precise motion-regulation.
In this design, a small rib-like structure protrudes from the bearing, fitting in with a corresponding notch/indentation in the rail. This flange guides the bearings along the rail while limiting contact points.
As with other bearing designs, linear bearings can be sealed off using metal or rubber. This practice reduces contamination and prevents lubrication leakage: see Sealed Bearings, below.
Sealed bearings have lubrication injected during the manufacturing process and are then sealed off. They are designed to both:
The seal is not necessarily permanent. Many bearings, for instance, employ a rubber seal that can be readily removed for maintenance (lubrication/cleaning) as necessary.
Like the journal itself, the bearing seal material needs to be carefully calibrated to pressure, temperature, and service life requirements. Selecting the proper seal material and design will maximize seal-life.
Generally, sealed bearings are used in conditions where either frequent re-lubrication is impractical, or dust/dirt contamination is a prime consideration.
The main advantage of open bearing designs is cost and ease of access for maintenance.
If frequent maintenance is planned, the additional costs of a sealed design may not be worthwhile.
In other environments, however, like those full of particulate matter from a manufacturing operation, employing seals (or self-lubricating bearings ) may be a virtual necessity.
Metal-sealed bearings are typically the cheapest sealed bearing options but are harder to access for maintenance.
Rubber-sealed bearings are typically more expensive than metal-sealed but can be more easily opened for re-lubrication. They cannot operate in particularly high temperatures, however.
As with bearings themselves, plastic polymers (PTFE in particular) are opening new frontiers for seals with superior performance characteristics.
Polymer seals, for instance, can stand up to more heat than rubber seals while offering improved corrosion- and chemical resistance compared to metal seals (this is important in any application where harsh cleaning chemicals risk damaging the quality of the seal, affecting its performance and lifespan).
In order to know how to choose plastic bearings, it’s important to first understand how they can fail. While the underlying function is always similar, different bearing types proliferate because different applications and operating environments place very different stresses on bearings.
Bearings fail prematurely due to damage from common issues like inadequate lubrication, particulate or corrosive contamination, overload, and improper installation. Bearing failure causes can vary widely depending on the material used and the operational environment.
Meanwhile, the operational and cost implications of bearing failure/maintenance/replacement can vary widely between applications. For a piece of manufacturing equipment that must be stopped daily for an inspection, for instance, frequent lubrication or occasional bearing replacement may be a non-issue. In these situations, the added cost of more advanced bearing solutions may offer few advantages. But applications at the other extreme (like bearings for satellites) may need to succeed in conditions where they will never be maintained.
Careful considerations of bearing material properties (e.g, mechanical, thermal, and electrical limits) is critical to preventing premature bearing failure. Evaluating manufacturer-supplied spec sheets, and utilizing tools like our Bearing PV calculator can help ensure successful outcomes.
We drive into key factors that can cause bearing failure in more detail below.
When thinking about bearing failure it's also worth learning what signs to look for to indicate that a bearing is getting ready to fail.
TriStar engineers have decades of combined experience in evaluating (and preventing!) bearing failure. We encourage you to reach out if you need assistance with your specific applications.
The relative importance of the bearing failure modes discussed above can vary widely depending on where a bearing is employed and how often it can be cost-effectively replaced or accessed for maintenance.
Environmental effects can alter a bearing’s expected lifespan by up to 90%. With this magnitude of environmental lifespan differential, selecting the right bearing for the right environment is instrumental to a design’s ultimate performance and reliability.
A few concise examples below demonstrate how bearings need to be carefully selected to reflect the conditions where they will be expected to operate.
Environments like steel mills, construction sites, and food processing lines include high levels of dust and other matter that can contaminate a bearing. Bearings that operate in these environments need to be sourced with this contamination risk in mind: particulates ranging from food debris to metal shavings become abrasive as they build up over time. This abrasion will affect both bearing seals (letting in more particles and/or water over time) and the bearings themselves.
You can read more about using bearings in dusty environments in our article here.
The dust contamination discussed above becomes worse as more grease accumulates inside a bearing. As lubricants become contaminated, their abilities to dissipate heat and reduce friction are sharply reduced. At best, bearing life is shortened. At worst, this contamination is a recipe for unplanned failures and downtime.
This makes regular cleaning of lubricated bearings essential—a key design concern for bearings that are difficult to access, will be maintained infrequently, or that operate in environments too dirty to be practically cleaned at required intervals.
While self-lubricating bearings may still require some level of lubrication, their reduced lubrication need creates key maintenance advantages for dirty operating environments
Vacuum environments tend to not only introduce maintenance difficulties but unique modes of failure. Plastic bearings, for instance, are often preferred in bearing designs that need to function in vacuums to eliminate lubrication requirements. But plastics need to be carefully selected for vacuum-use: some plastics exhibit out-gassing and particulate-shedding that cannot be easily vented in a vacuum.
Any bearing requiring regular lubrication comes with the risk of lubricant contaminating the surrounding environment. When facing design requirements for clean operation (stemming from ISO standards, government regulations, or client demands for sustainable best practices), leakage effectively becomes a mode of bearing failure. With this risk in mind, self-lubricating plastic bearings offer important advantages for clean operation in these environments.
Evaluating bearing material properties is key to success for any application. A plastic vs metal bearings comparison, for example, reveals that plastic bearings are lighter and more corrosion-resistant, though metal bearings may offer higher load capacities. Each material has benefits and potential downsides to consider.
Wood may not be the first material you think of for bearings, and it is relegated to specialty applications today. But wood bearings provide useful historical context: they illustrate that engineers have been carefully selecting materials to fit bearing performance criteria for much of recorded history.
There is evidence that Phoenician boat builders used wooden bearings for rudders as early as years ago. The right woods are corrosion resistant, allowing them to thrive in submerged applications like rudders or propellers shafts. In the old-world, the ultra-hard wood Lignum Vitae was a popular choice--it’s natural oils provided built-in lubrication while its extreme density helped it hold up under stress. Later, bearing makers would impregnate wooden bearings with animal oils to achieve a similar self-lubricating effect.
Today, composite bearings offer key performance advantages over wood in underwater applications, but wooden bearings were the first example of a bearing material being carefully selected for desirable mechanical bearing properties.
Bronze is a commonly used material that comes in a huge variety of different alloys and compositions--this variety makes bronze a popular choice of bearing material, as a material very close to the precisely desired specification can be sourced. Bronze bearings have strong characteristics for shock, impact, and corrosion resistance.
Bronze bearings do require lubrication both at installation and during operation, which can make them a poor choice for designs that are difficult to access for frequent maintenance. This limitation is why replacing bronze bearings with a self-lubricating option (see below) offers an attractive proposition for many companies.
A common traditional choice for industrial applications, steel bearings can handle extremely high loads and high rpms. Stainless steel bearings offer improved corrosion resistance compared to other steel grades, but potential drawbacks still include relatively high weight and high noise.
Another common traditional choice, cast iron bearings have a sufficiently low friction coefficient to be employed on a steel shaft. Cast iron glazes over time which helps reduce wear.
For bearings, PTFE is not only useful as a structural material but as a lubricating medium for self-lubricating bearings (more on this below).
Useful properties include low friction coefficient, corrosion resistance, low electrical conductivity, hydrophobia, and a broad range of tolerable temperatures.
So, which of these plastics is best? As with the other bearing selection parameters discussed in this article, it all depends on the application. In fact, these plastics can be blended with one another, or with non-plastic materials, to generate the desired characteristics in terms of performance, maintenance needs, and cost.
For a detailed look at the properties of different plastic polymer offerings from TriStar, explore our materials database here.
Self-lubricating plastic materials provide low-maintenance bearing options, eliminating the need for regular lubrication and reducing downtime.
These bearings have a lubricant like PTFE, graphite, or silicon integrated with the rubbing surface of the bearing itself. As moving parts rub together, this lubricant dynamically disperses over time.
Self-lubricating plastic polymer bearings utilize two different mechanisms to transfer lubrication media:
For more on how self-lubricating polymers work, check our our expanded blog post on the subject.
Employing one of these designs is important in applications where frequent re-lubrication is impractical or unduly costly, in extremely high-friction environments, or in environments where traditional liquid lubricants represent too great a risk for contamination/leakage.
Because inadequate lubrication is the number-one cause of bearing failure, ending the need for lubrication not only simplifies maintenance but dramatically reduces premature wear that accumulates during inevitable maintenance intervals. Grease and other lubricants also exacerbate contamination issues by helping dust and dirt stick in the bearing mechanism, another long-term wear-driver that self-lubricating options eliminate.
TriStar is the exclusive North American distributor of Rulon, a family of PTFE-based plastics purpose-built for the functional requirements of demanding applications like bearings. Like other plastics, it is available in a wide variety of formulations (in fact, over 300).
For a deeper look at Rulon and some key formulation options, please see our white paper:
More advanced approaches to metal bearing design allow for self-lubricating capabilities while retaining some of metal’s desirable structural characteristics.
TriStar’s TriSteel™, for instance, consists of a special polymer lining with a metal backing. The liner is impregnated into a sintered porous bronze inter-layer. Both materials can be precisely specified depending on the application. This design takes advantage of steel (zinc/copper-plated or stainless) for structural and mechanical support while utilizing a polymer liner for improved wear characteristics and self-lubrication.
Learn more about TriSteel on our product webpage or view the brochure.
Composite bearings are made from a combination of materials, such as fiber-reinforced resin or plastic. The composite material can be combined with PTFE to create a lightweight, self-lubricating design.
Composite bearings offer dramatic weight advantages compared to metal-based bearings. Read about some other benefits of composite bearings here. The composite itself can be customized to meet specific application requirements. A composite liner can be applied on a metal-backing for added strength.
TriStar’s CJ composites are a great example of a composite bearing solution. This design utilizes multiple layers. The innermost layer consists of a synthetic fiber/PTFE layer. The second layer consists of epoxy coated high-angle glass filaments. The outermost layer consists of epoxy coated low-angle glass filaments.
This construction allows for a bearing that is lightweight, high-strength, and fatigue-resistant, often an ideal choice for non-lubricated high-load/low-speed applications. CJ bearings provide excellent resistance to impact and shock loads. They are also capable of withstanding a high degree of shaft misalignment: the composite wall acts like a spring and the thicker the wall section of the bearing the greater the deflection for a given load.
For more information on CJ Composite bearings view our CJ web page or check out the brochure.