Surplus Bearings

What is a Bearing?

Bearings are essential components of a mechanical system that facilitates rotary or linear motion with minimal of friction. It would be almost impossible to design and operate a mechanical or electro-mechanical system without bearings. There are a wide range of bearings depending on the applications - ball bearing is the most common type bearing used in everyday application such as in a bike. Other types of bearings include roller bearings, sleeve bearings (no moving parts), needle bearing (thin rollers). Thrust bearings are a special type of bearings used in car wheels due to lateral movements (side-wise movements). as well as impact loads. Where used - machine tools, hand tools, cars, trains, airplanes, electrical motors, turbines (water, steam, gas) - almost anything that moves uses bearings.

How to Find Bearing Numbers by Size?

Bearing part numbers help you to identify the type, size and general uses for a bearing. The part number is usually stamped or printed on the bearing. There are three different types of bearings. Ball bearings are loose spheres that separate the races in a bearing. Roller bearings are circular shaped and function the same way as ball bearings. A needle bearing uses rollers to reduce friction. Occasionally, you may need to replace a bearing, but due to wear and accumulation of dirt, the part number may not be legible. 

You can identify the replacement bearing by the bearing measurements:
d=inside diameter, D=outside diameter and B/T = width diameter

How to Find Bearing Numbers by Size?

Bearing part numbers help you to identify the type, size and general uses for a bearing. The part number is usually stamped or printed on the bearing. There are three different types of bearings. Ball bearings are loose spheres that separate the races in a bearing. Roller bearings are circular shaped and function the same way as ball bearings. A needle bearing uses rollers to reduce friction. Occasionally, you may need to replace a bearing, but due to wear and accumulation of dirt, the part number may not be legible. 

You can identify the replacement bearing by the bearing measurements:
d=inside diameter, D=outside diameter and B/T = width diameter

Cleaning & Lubricating Ball Bearings

  1. Soak the ball bearings with volatile degreaser and apply motor spray on them. 
  2. Shake the bearing case vigorously to remove dirt. It will loosen and remove the dirt trapped inside the bearings.
  3. Soak the bearings for another 15-30 minute. Repeat the process until the oil/liquid is clean. Dry the ball bearing with hot air gun/ hair blower to prevent rusting of the bearing.
  4. Apply light oil on the bearings, give it about 20 minutes to penetrate the seals and then clean the outsides up.

How to Avoid Bearing Corrosion?

It is crucial that you should not expose bearings to the presence of water for a long time, as it will lead to rust and corrosion. It will also cause the premature failure of the bearings, which can affect the machine performance and productivity. As a result, it will increase your operating costs. Also, make sure to wear gloves when handling bearings. Perspiration can also lead to rust and corrosion

What is a Deep Groove Ball Bearing?

Deep groove ball bearings are the most common type of ball bearing. They are commonly used in electric motors and in household appliances, car motors, office machinery, automation control, and garden and household tools. They have deep raceway grooves and their race dimensions are close to the dimensions of the balls that run inside.

Deep groove ball bearings come in many sizes, materials and varieties according to consumer needs, including special industrial uses such as high-temperature applications. High-temperature bearings are made to withstand temperatures up to 350°C (660°F) and are suitable for machines used in the metals industry or for industrial ovens.

What a bearing grease is the best?

The answer is, "it really depends." The selection of the best bearing lubricant (whether grease or oil) will depend on the application conditions. With a wide variety of greases and oils available, solutions are available for most applications; however, there is no perfect grease whether natural, synthetic, micro-filtered or otherwise.

Every grease has strengths and weaknesses in its performance and consequential monetary costs. For example, high temperature greases typically can't handle high loads very well. "Quiet" greases may break down at high temperatures.  Additives have benefits but some drawbacks too.  So there is no single best grease for bearings; it really comes down to the application and what characteristics are most important (and which are less).

Can bearings be refurbished?

For small bearings it is uneconomical to attempt to refurbish a bearing product. However, for larger size bearings (6 inch bore and above) there potentially could be economic gains. In particular, bearings such as slewing rings, cylindrical roller bearings, and spherical roller bearings are candidates for refurbishing.

What is the difference between a solid base and hollow base?

Solid Base Housings are manufactured with no cavities and no filling; they are stronger than hollow base and have no traps for bacterial and fungal growth. In a thermoplastic housing, a solid base won’t crumble under steam or high-pressure wash down. Hollow base saves material and weight to reduce cost. Some back-fill the hollow base with an epoxy resin to eliminate traps for bacterial growth, however this does not improve strength, can create an uneven mounting surface, and water can penetrate between the housing and filling materials which will induce cracking.​

What is the difference between a solid base and hollow base?

Solid Base Housings are manufactured with no cavities and no filling; they are stronger than hollow base and have no traps for bacterial and fungal growth. In a thermoplastic housing, a solid base won’t crumble under steam or high-pressure wash down. Hollow base saves material and weight to reduce cost. Some back-fill the hollow base with an epoxy resin to eliminate traps for bacterial growth, however this does not improve strength, can create an uneven mounting surface, and water can penetrate between the housing and filling materials which will induce cracking.​

5 Things You Should Not Do To Your Bearings

Taking care of your bearings in a proper manner is an important process to increase their lifespan and enhance bearings performance. Often times when bearings are mishandled, it will lead to premature failure.

These are a few things that you should not do to your bearings to avoid early breakdowns:

  1. Applying too little grease
    Applying lower than the recommended amount of grease may increase temperatures and metal contact, leading to increased friction and damaging the bearing through extreme wear. As a result, it leads to early failure in your bearings.
     
  2. Applying too much grease
    In fact, over-greasing causes even more damage to the bearings than under-greasing. Applying too much grease will lead to heat-build up as there is nowhere for heat to dissipate and along with the internal churning of the bearing, the excessive grease will then travel outside the bearing and hardened on the surface, preventing the entry of any other grease. The restricted lubricant flow and high temperature then results in lubrication failure and in turn, bearing failure.
     
  3. Placing your bearings on the ground
    Avoid placing your bearings on the floor for long hours even if they are new and tightly sealed in a package. This is due to the direct contact between the ground and the bearings and thus heat transfers quickly from the floor to the bearings. Furthermore, the ground surface is also exposed to moisture that could seep into the packaging of the bearings and eventually to the bearing itself. Therefore, it is strongly recommended that whenever you receive your bearings, place them on high surfaced objects such as a wooden palette that acts as an insulator without any direct contact between the ground and bearings so that heat transfer is slow; the same goes for moisture.
     
  4. Hammer or exert direct force
    While bearings are relatively hard, using metal hammers (e.g. steel) that have greater hardness could cause serious harm to the bearings.
    Usually, the tight fit configuration is meant for either the shaft or the housing. There have been cases whereby both components have tight fits due to their deviation which dictates how far away from the nominal dimension, the actual measurement is allowed to be. For example, if the shaft has the maximum deviation of +10μm and housing bore has the minimum deviation of -10μm, this would mean that the shaft has a slightly larger diameter than its standard measurement while the housing has a marginally smaller diameter than its actual dimension. Hence, the larger shaft and the smaller housing are unable to fit into each other due to tightness.
    When encountered with this situation, some would use a hammer or similar tools to pound on the bearings, hoping to "loosen" the fit. However, not only does this action unable to help with loosening the fit, it causes severe damage to the bearings. This causes the rolling elements to be misaligned and also wears out the bearings due to hammering.
     
  5. Exposing your bearings to moisture
    While most bearings have a strong resistant to water or damp surfaces, it is still susceptible to rust under extreme condition or when they are exposed to moisture for a long period of time, resulting in water contamination. It is important to note that even a little rust has a huge impact on the lifespan of the bearings. While bearing failure may take a long time, sometimes even up to several years to even be noticeable, the life expectancy of bearings are significantly reduced. Therefore, it is important to keep your bearings sealed in their original unopened package (until needed) and stored in a clean and dry environment.

What is Dismounting?

Dismounting is the opposite process of bearing mounting; it refers to the removal of ball bearings from a component. Bearings are sometimes dismounted to maintain or replace other components of the machine. These bearings are often re-used.

Just like bearing mounting, there are several types of dismounting methods:

Dismounting Methods

1. Manual dismounting
- From a cylindrical shaft seat
- From an adapter sleeve
- From a withdrawal sleeve
2. Dismounting with hydraulic assisted tools
3. Dismounting using oil injection method
4. Dismounting using heat

Mounting Bearings With A Cylindrical Bore

For bearings with cylindrical bore, the inner ring is mounted first. Still, if the bearing is non-separable, the tighter fit needs to be mounted first. If the ring is separable, then the inner ring will be mounted separately.

In both cases, the mounting can be done mechanically – and this procedure is called "cold mounting", or by heating the bearing previous to mounting – and this procedure is referred to as "hot mounting". A third method is hydraulic mounting, which is used mostly for large bearings.

For small bearings, meaning bearings with a diameter under 80 mm, both mechanical (cold) mounting and hot mounting can be used, but the preferred method is the mechanical or hydraulic press. For the press fitting method, a mounting tool is placed on the inner ring, then the bearing is pressed on the shaft, slowly, until the side of the inner ring rests against the shaft.

Mounting Bearings With A Tapered Bore

Bearings with a tapered bore are mounted on a tapered shaft or on a cylindrical shaft with an adapter or withdrawal sleeve. This is always done with an interference fit, the degree of interference being determined by how far the bearing is moved up onto a tapered shaft seat.

Small bearings with a bore diameter lower than 80 mm can be driven up onto the seat using a bearing fitting tool or a lock nut. For bearings mounted with an adapter sleeve, a hook or impact spanner should be used, and for those mounted with withdrawal sleeves, a bearing fitting tool or a nut are the best tools to use.

For medium-size bearings with a tapered bore, the proper bearing mounting tool is the impact spanner, but the drive-up method and the oil injection method can also be used. The last two techniques apply also to large-size bearings. For bearings with bore diameters greater than 200 mm, hydraulic nuts are recommended, and where applicable, SKF recommends using shafts and sleeves with grooves and ducts for the oil injection method.

The installation of large bearings using hydraulic nuts is applicable to tapered shaft seats, adapter sleeves and withdrawal sleeves. The hydraulic nut is positioned onto a threaded section of the shaft, or onto the thread of the sleeve, and rests on the inner ring of the bearing or on the shaft. When oil is pumped into the hydraulic nut, the piston is displaced axially thus the inner ring is driven up the taper, and mounted safely and accurately.