Choosing the Right Bearings for Your Application
Selecting the optimal bearings for a piece of equipment requires careful consideration of the application requirements. The wrong bearings can lead to poor performance, high wear, and frequent failures.
Bearing Types Overview
Major bearing categories include:
- Ball bearings - use balls between inner and outer races. Allow both radial and axial loads.
- Roller bearings - use rollers between races. Optimized for heavy radial loads.
- Fluid bearings - fluid film supports the shaft. Very low friction.
- Magnetic bearings - no contact. Useful in high speed, vacuum, or sterile applications.
Load, Speed, and Environmental Factors
Consider the following when selecting bearings:
- Radial and axial load capacity needed
- Shaft rotational speeds
- Shock and vibration levels
- Ambient temperatures
- Contamination and corrosion resistance requirements
For example, split pillow block housings allow easy installation around shafts. Angular contact ball bearings handle combined radial and axial loads. Ceramic rolling elements perform well at very high speeds. Stainless steel bearings resist corrosion in harsh environments.
Bearing Materials
| Material | Characteristics |
|---|---|
| Steel | Most common. Low cost but heavier than other materials. |
| Ceramic | Higher hardness than steel. Used in high precision or high temperature applications. |
| Plastic | Low loads only. Good resistance to corrosion and electricity. |
Lubrication Needs
Lubrication is vital to separate rolling and sliding surfaces in bearings. Greases or oil help prevent wear and reduce friction. Always follow the manufacturer's lubricant recommendations.
Sealed bearings are lower maintenance but cannot be relubricated. Open bearings must be periodically greased or oiled.
With proper bearing selection and maintenance, equipment can achieve long and reliable service lives from these compact components.
Bearing Types Overview
Bearings are machine elements that allow components to rotate or slide smoothly against each other. Selecting the right bearing type for an application requires understanding the design, capabilities, and limitations of different bearing options.
Plain Bearings
Plain bearings, also called slide bearings, are the simplest type. A shaft or journal slides directly against the bearing surface. The main types are:
- Bushings - Cylindrical lining in a housing
- Washers - Flat discs with a hole for the shaft
- Thrust bearings - Support axial loads
Plain bearings are low cost but have higher friction than rolling element bearings. They require lubrication to prevent excessive wear.
Rolling Element Bearings
These bearings use rolling elements like balls or rollers between two raceways to reduce friction. Types include:
- Ball bearings - Use spherical rolling elements to handle radial and axial loads
- Roller bearings - Cylindrical rollers for primarily radial loads
- Tapered roller bearings - Can support heavy radial and axial loads
- Spherical roller bearings - Self-aligning while accommodating misalignment
Rolling element bearings have less friction, operate at higher speeds, and last longer than plain bearings. They require proper lubrication and sealing.
Fluid Bearings
Fluid bearings, also called hydrodynamic or hydrostatic bearings, use a fluid cushion or film to support the shaft. The main types are:
- Hydrodynamic - Fluid wedge generated by shaft rotation
- Hydrostatic - External pressurized fluid fed into the bearing
Fluid bearings offer very low friction and high speeds. But they require external pumping and piping for the fluid.
Overall, bearing selection depends on load capacity, rotational speed, expected life, noise, temperature range, and environmental conditions.
Load, Speed, and Environmental Considerations for Bearing Selection
Choosing the optimal bearings for an application requires evaluating the expected loading, speed, and operating environment conditions.
Load Considerations
The bearing load types, magnitudes, and directions must be assessed:
- Radial load - perpendicular to shaft axis
- Axial/thrust load - parallel to shaft axis
- Combined radial and axial loads
Load capacity needed can be calculated based on forces exerted by gears, pulleys, friction, impact, etc. A bearing's dynamic and static load ratings must exceed the application loads with a safety factor.
Speed Considerations
The operating rotational speeds and needs for high precision will influence bearing selection. Key factors include:
- Maximum/minimum shaft speeds
- Speed variation and reversals
- Accelerated speeds during start-up or operation
- Oscillations or critical resonance frequencies to avoid
High speed applications above 500 rpm may require specialized bearings designed for handling centrifugal forces.
Environmental Conditions
The bearing environment including temperatures, contamination, moisture, etc. determines material and sealing requirements:
- Ambient temperature range
- Temperature gradients or cycling
- Chemical or caustic agents
- Dust, dirt, water ingress potential
For example, stainless steel bearings resist corrosion in wet environments. Ceramic bearings withstand very high temperatures over 750°F (400°C). Appropriate seals or shields should be used to protect bearings.
Carefully considering the expected bearing loads, rotational speeds, and environmental conditions enables selecting the bearing type, size, housing, and features needed for optimal performance and service life.
Bearing Materials - Steel, Ceramic, Plastic
Bearings are made from different materials that are selected based on the application requirements. Common bearing materials include steel, ceramic, and plastic.
Steel
Steel is the most common bearing material due to its versatility and low cost. Different types are used:
- 52100 chrome steel - Highly hardened with good wear resistance
- Stainless steel - Corrosion resistant for washdown or marine environments
- Tool steel - High strength for heavy load capacity
Steel bearings have a long fatigue life at high loads and speeds. They are tough and relatively easy to machine. However, steel is susceptible to corrosion and may require surface treatments or coatings.
Ceramic
Ceramic materials like silicon nitride and zirconia are used when high precision, electrical insulation, or low thermal expansion is needed. Benefits include:
- Low density - Reduces centrifugal forces at very high speeds
- Hardness - Resists wear even with poor lubrication
- Corrosion resistance - Performs well in acidic or caustic environments
However, ceramics are more brittle than steel and vulnerable to shock loads or contamination. This limits their use to precision applications with controlled conditions.
Plastic
Plastics such as nylon, polyacetal, and polytetrafluoroethylene (PTFE) are common for low load applications. Advantages include:
- Low friction and noise
- Good chemical resistance
- Electrical and thermal insulation
Maximum speeds are typically below 10,000 rpm for plastic bearings. They cannot withstand high temperatures or heavy loads compared to steel or ceramic. But plastics are a lightweight, low-cost option for light duty applications.
The operating conditions and application requirements determine the optimal bearing material for performance, life, and cost.
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Bearing Lubrication Needs
Proper lubrication is essential for bearings to achieve optimal performance and service life. Lubricants reduce friction and wear while removing heat from the bearing components.
Functions of Bearing Lubricants
Key functions of lubricants include:
- Separating surfaces - Prevent direct contact of rolling elements and races
- Cooling - Transfer heat generated by friction out of the bearing
- Contaminant flushing - Clean away dirt, debris, and metal particles
- Corrosion prevention - Protect against rust with oil film
Grease vs. Oil
The most common bearing lubricant types are grease and oil:
- Grease - Thick lubricant with soaps to adhere to bearing surfaces. Used for simpler applications.
- Oil - Flows easily to lubricate high speed bearings. Requires constant replenishment.
Greases simplify maintenance with less frequent lubrication needed. Oils handle heat better for high speeds, but require recirculation systems to continuously supply oil.
Factors in Selection
Consider these factors when choosing bearing lubricants:
- Base oil viscosity - Thicker oils for higher loads, thinner for high speeds
- Operating temperatures - Ensure grease consistency and oil viscosity stay in grade
- Seal compatibility - Avoid swelling or deterioration
- Noise levels - Some greases are quieter than others
Always check manufacturer recommendations for optimal lubricant selection and relubrication intervals. Properly lubricating bearings is essential to maximize machine reliability.
How to use your Amazon Prime to buy Bearings, Balls & Bushings
Amazon Prime provides fast, free shipping on millions of products - including bearings, bushings, ball bearings, and other industrial supplies. Here are some tips on using Prime to purchase bearings and related components.
Search for Reputable Brands
Look for well-known bearing brands like SKF, Timken, NSK, FAG, NTN, etc. While Amazon offers some generic unbranded bearings, purchasing from an established manufacturer helps ensure quality and proper specifications.
Check Specifications Carefully
Double check that the bore diameter, outside diameter, width, material, load rating, precision grade, and other specifications match your application requirements. A bearing with the wrong dimensions or capacity ratings will not function properly.
Compare Prices
Amazon displays pricing and shipping costs upfront for Prime eligible items. Compare prices across sellers to find the best deal on the bearings you need. You may be able to purchase inexpensive imports or bundles for additional savings.
Check Item Locations
For fastest delivery, look for items that ship from Amazon fulfillment centers in your region. Delivery times will be longer for products shipping directly from third party sellers.
Consider Business Prime
If purchasing bearings for a business, consider switching to a Business Prime account. Business Prime offers additional benefits like quantity discounts and payment terms while providing quick shipping on bulk orders.
With millions of eligible items, Amazon Prime is a convenient way for engineers, maintenance teams, and operations managers to quickly purchase quality bearings, bushings, ball bearings and other industrial components needed to minimize downtime.
How To Choose The Right Bearing For Your Application?
Choosing the right bearing for your application requires careful consideration of several factors. Here are some key steps to follow:
- Determine the bearing type: Based on the application requirements, identify the appropriate bearing type. For example, ball bearings are suitable for small shafts, while cylindrical roller bearings, self-aligning roller bearings, and tapered roller bearings are used for large shafts.
- Consider the load capacity: The load capacity is the amount of load a bearing can handle and is one of the most important factors when choosing a bearing. Bearing loads can either be axial (thrust), radial or a combination.
- Check the space available: In mechanical design, the size of the shaft is typically determined first, and then the bearing is selected based on the size of the shaft. If the radial space of the bearing installation position is limited, a bearing with a smaller radial section height should be used.
- Determine the rotation speed: Some bearings can withstand high speeds. The presence of a cage for cylindrical roller bearings and needle bearings allows for greater speeds than other types of bearings.
- Consider the usage environment and operating conditions: The bearing should be appropriate for the machine’s usage environment and the operating condition that is being demanded of the bearing.
- Check availability and maintenance: The bearing should be easy to acquire replacement bearings and it should facilitate maintenance/inspection of the machine.
- Seek expert advice: If you are unsure about which bearing to choose, consult with an expert who can help you select the right bearing for your application.
