A. We provide the best quality bearings with reasonable price, low friction, low noise and long service life.

B. With sufficient stock and fast delivery, you can choose our freight forwarder or your freight forwarder.

C. The best service provided by a well-trained international sales team.

100% quality check, once your bearings are standard size bearings, even one, we also accept.

Generally speaking, if the goods are in stock, it is 1-3 days. If the goods are out of stock, it will take 6-10 days, depending on the quantity of the order.

Yes, we can provide a small amount of free samples. Do you mind paying the freight?

We have too many bearing series numbers. Sometimes we can't put them all on Alibaba. Just send us the inquiry and we will be very happy to send you the bearing details.

The best way to get an exact replacement is to give us the full part number on the invoice or despatch note that came with the original bearing. It is quite likely that you no longer have the paperwork. In that case, measure the bearing: the bore (internal diameter), the OD (outer diameter) and the width. Is the bearing open or does it have metal shields or rubber seals?

Identify any other features of the bearing. Does it have a flange on the outer ring? Is the inner ring the same width as the outer ring or wider? Can you see the retainer? If so, is it a steel retainer or made of a different material?

The fuller the description, the better. Is there a reference marked on the bearing? The reference may indicate the bearing material such as chrome steel or stainless steel and possibly confirm any other features such as the tolerance grade or the radial play.

The temperature limit for bearings depends on the material of rings and balls, the retainer (cage), any closures such as rubber seals and finally, the lubricant. Chrome steel can support the same loads up to 120°C constant and 150°C intermittent. Above that, the load capacity drops noticeably. For 440 grade stainless steel, the figures are 250°C constant and 300°C intermittent.

The standard retainer for chrome steel bearings is steel so will cope with the same temperatures. Stainless steel bearings usually have a stainless steel retainer so no problem there either. However, bearings can have a nylon or polyamide retainer which can limit the upper temperature to 100°C - 120°C depending on material.

Bearing shields will cope with the same temperatures as the rings and balls but rubber seals should not be used above 110°C.

The next limiting factor can be the lubricant. Different oils and greases have different temperature ranges. As long as the other materials in a bearing are suitable, we can offer bearings with lubricants that will cope with -80°C all the way up to 300°C.

teel ball bearings can rust. Bearings made of chrome steel will rust easily which is why they leave the factory with the outer surfaces coated with a protective oil. Stainless steel bearings are much more corrosion resistant but will still rust when coming into contact with certain substances.

Stainless steel bearings are corrosion resistant or very corrosion resistant depending on the grade of steel. 440 grade stainless steel bearings have good resistance to moisture, water and many weak chemicals which is why they are very popular in the food and beverage industries. They will rust quickly if exposed to many strong chemicals, acids, alkalis and salt water.

The “marine grade” stainless steel is 316 grade. This is much more corrosion resistant than 440 grade but, as it cannot be hardened by heat treatment, it is much softer. 316 stainless steel bearings can only support much lower loads and speed than 440 grade bearings but is suitable for many marine applications.

Full ceramic bearings have excellent corrosion resistance and can be used with seawater and many aggressive chemicals.

Yes - radial ball bearings with a retainer (or cage) are designed to take primarily radial loads but have an axial load capacity. The amount of permitted axial load depends on the bearing dimensions and is often given as an approximate percentage of the bearing’s static radial load rating.

Bearings with a greater difference between the bore diameter and outer ring diameter can take larger axial loads as a percentage, sometimes up to 50% of the radial static load. This also partly depends on the depth of the bearing raceway. Thin section bearings have shallower raceways which reduces the axial load capacity.

There are other factors which determine how much axial load a bearing can handle. Bearings subjected to a heavy radial load and bearings with a moment (tilting/misalignment) load will have a reduced axial load capacity.

If the bearing needs to cope with a heavy axial load, an angular contact bearing should be used. These have a different internal design allowing them to handle much greater axial loads than standard radial ball bearings.

Bearings with a flange on the outer ring are easier to mount in a housing then standard bearings as there is much less reliance on the housing tolerance to hold the bearing securely. The flange helps to prevent the bearing from moving in an axial direction when exposed to axial loads or vibration.

The flange is also an advantage when the housing fit changes due to thermal expansion. In these conditions, a flanged bearing will stay in place under an axial load. Although flanged bearings are more expensive than their non-flanged counterparts, they are very popular with designers for the above reasons.

Noise in a bearing is caused by a number of factors that increase vibration. Rough or damaged balls or raceways, poor ball/raceway roundness, contamination inside the bearing, inadequate lubrication, incorrect shaft or housing tolerances and incorrect radial play can all contribute to noise.

A good quality, low noise bearing will have excellent surface finish on balls and raceways and the roundness of the balls and bearing rings will be very closely controlled. Specifying a radial play that allows the bearing to operate with almost zero radial play when in use will help to control noise. If the shaft or housing tolerances are incorrect, the bearing can be too tight leading to excessive noise while poor shaft or housing roundness can distort the bearing rings, also causing the bearings to be noisy.

In a good quality bearing, a low noise lubricant is recommended as finely filtered greases will allow the bearing to run quietly due to the absence of larger solid particles. Poor fitting practices can cause dents in the bearing raceways which will greatly increase vibration. Finally, a low noise bearing must be free of contaminants so, if the bearing is not used in a very clean environment, protection against dirt, such as contact seals, should be considered.

A quality ball bearing is a thing of great precision. The rings and balls are machined to fine tolerances and high levels of roundness. The balls and the ball tracks (or raceways) are highly polished so the bearing will rotate very smoothly and easily. Frictional torque or in simple terms, turning resistance, is extremely low.

Unlubricated bearings have the lowest turning resistance but steel ball bearings should be lubricated unless turning speeds are very low. They can be lubricated with a low torque instrument oil but, depending on speed and running time, this may mean they need to be constantly oiled with an oil bath, jet or spray. A simpler alternative is to use a shielded bearing, pre-lubricated with a finely filtered, low torque grease to provide a constant film of oil between balls and raceways while also helping to radiate any heat away from the points of contact.

Imagine the heat, vibration, turning resistance and rapid wear that would result from rotating a steel shaft, at speed, in a steel housing without the use of bearings. The noise and the excessive amount of steel debris would soon let you know that something was wrong. We have come a long way from the days of packing grease or fat between wooden cart wheels and axles to reduce friction and with constant advances in manufacturing and steel and lubricant technology, the number of low friction options for a wide variety of products continues to grow.

How to measure bore diameter

Quick. You need replacement bearings, but you’re not sure what measurements you require. It’s time to inspect the old bearings and possibly carry out a few measurements.

You may be in luck. If the bearing still has a visible reference number engraved onto it, you’re sorted. Just call SMB Bearings and quote this code. If not, you might be able to dig out the original order documentation with the reference on out of the depths of your filing cabinet. If neither of these are possible, it’s time to get measuring.

There are three main measurements to a bearing. The bore diameter (sometimes referred to as inner diameter or ID), the outer diameter (OD) and the bearing width.

While all three measurements are important, the bore diameter receives particular attention, as this figure is entirely dependent on the shaft size. It should be noted that the shaft diameter does not always equal the bore diameter. In many cases, the shaft diameter is often a tiny bit larger than the bore size, to help the bearing to fit well on the shaft over time. This means induction heaters are required to mount bearings onto the shaft while the material is warm and malleable.

 

How to measure bearings

To obtain these three measurements, you could attempt to use a ruler.  Many people do this, but it isn’t very accurate.

The best way for most of us to measure bearings is by using digital Vernier calipers. This measurement tool is used to gauge internal and external distances.

A good caliper will have an accuracy of plus or minus 0.02 mm or roughly a ten thousandth of an inch. Suddenly, that ruler you were tempted to use pales in comparison although neither compete with the air gauges that the bearing manufacturers use. These can be accurate to within 0.0002mm or less than 10 millionths of an inch.

Most calipers allow you to switch between millimeters and inches with the touch of a button, ready to measure both imperial and metric bearings.

Ready to measure the bore diameter? Here’s how you do it.

Turn your digital calipers on and zero the data reading in the closed position. Place the bearing onto the inner measurement side of the calipers, roll them out to as far as the bearing will allow and note down the measurement displayed. You should wiggle the calipers inside the bearing inner ring to make sure they sit across the widest part.

Repeat the process using the external measurement side of the caliper to calculate the outer diameter of the bearing. This time, roll the calipers in a closing direction to obtain the outer diameter measurement.

Using the external measurement side once more, measure the width of the bearing, which is done in the same way you would measure the diameter.

With your three measurements to hand, you can now get in touch with SMB Bearings to find out which bearings from our UK stock are a match.

Both oils and greases have their advantages and we’ll forgive you for using the terms interchangeably.  Technically though, grease is defined as an oil mixed with a thickener. Because of this, oils tend to provide higher running speeds, but will not stay in place as effectively. Therefore, continuous re-application may be needed whether the bearing is sealed or not.

For many applications, grease is more convenient as it stays inside the bearing for longer. It benefits from both the properties of the base oil and the added thickener; both having positive effects on the performance of the bearing and its lifespan.

When choosing between oils or greases, it’s important to remember frictional torque levels for a greased bearing are briefly higher to start with, as the bearing begins to spin from stationary. This is because thicker grease takes a short time to ‘run in’ and get distributed inside the bearing. It’s most likely not a problem for many continuous applications, but this could cause problems for stop start equipment.

Bearing shields and seals are designed to prevent particles from entering, and to keep the vital grease inside the bearing. Bearing shields do not make contact with the inner ring. This means they do not increase starting or running torque but are not very effective at preventing washout.

For greater protection against contamination and lubrication loss, contact seals made of nitrile rubber can be used to seal the bearing inner ring. It should be noted however that contact seals produce much higher frictional torque levels than shields, so must warrant the added protection.

The middle ground is non-contact seals. These are also made of nitrile rubber, but do not rub against the bearing inner ring. This means these seals don’t affect torque or maximum speed. They offer more protection over metal shields, but if you need the ultimate seal, you may be better off with the contact type.

For the greatest protection against washout, a highly water resistant grease is recommended. Food grade greases are designed to withstand regular steam cleaning or wash-downs with cleaning chemicals. PFPE greases, many of which are also food grade, will perform the same task but have even higher resistance to chemicals.

Firstly, it’s important to consider what we mean by the term ceramic bearings, as it confusingly encompasses both hybrid and full ceramic ball bearings — each of which should be treated slightly differently.

In brief, hybrid bearings use ceramic balls, paired with metal inner and outer rings, whereas full ceramic bearings are entirely made from ceramic material.

Now you’re clear on the difference between full ceramic and hybrid options, how do you clean your bearings to keep them dirt free and performing optimally? The good news is that ceramic bearings are inherently more resistant to dirt, water and corrosion than their stainless-steel counterparts, so the maintenance process is a breeze.

Cleaning hybrid ceramic bearings

Lubrication isn’t required for full ceramic bearings, but it is often used with hybrid bearings, especially when performing at higher speeds. To clean and relubricate a hybrid ceramic bearing, firstly identify the closure type.

Only circlip retained bearing shields may be removed for cleaning or relubrication purposes. Use a needle on one end of the circlip to gently remove it from the outer raceway. The shield can then be removed by easing the needle into the gap between inner ring and shield and levering the shield out. For rubber seals, prise out the seal from the inner lip. You can use a penknife or small screwdriver but do not push it too far into the bearing or you may damage the retainer.

Following this step, use a degreaser and some paper cloth to make sure you fully clean away all old grease, you can also opt to soak the bearing if you wish. Once satisfied that the bearing is completely grease-free, use a lint-free cloth to dry the bearing. At this point, take the time to visually inspect the bearing for signs of wear. Make sure the bearing surfaces are completely clean and oil free before you lubricate the bearing.

Maintaining your full ceramic bearings

Full ceramic bearings are maintenance free. However, they can be washed using regular tap water or a standard bearing cleaner product if required. Make sure the bearing is completely dry before replacing it. These bearings do not need lubricant to operate, so there is no need to add an oil or grease at this stage. However, lubrication can be used to keep the ceramic material from wearing down prematurely and to extend bearing life.

As most of our bearings are small and light, we ship most bearings by UK or international post. Higher value orders can be sent by insured post, for example Royal Mail Special Delivery or international tracked air post. For heavier or more urgent parcels, we also use economy and express courier services such as Fedex, TNT, Parcelforce and DPD.

Some customers prefer to ship via their own courier accounts, for example Fedex, TNT, UPS or DHL. This is not a problem and, in most cases, our logistics department can book the consignment online on behalf of the customer.

Plastic bearings are ideal if you need corrosion resistant bearings. Where some metal bearings would corrode over time, plastic bearings will stay intact. This is because plastic doesn’t absorb any moisture. They are also much lighter than steel bearings.

As a result, plastic bearings are a great option for applications that exposure bearings to regular washdowns, like the equipment in the food industry. Similarly, plastic bearings are suitable for applications requiring non-magnetic bearings. It is important to note that plastic bearings are made to looser tolerances than our precision bearings and are referred to as “semi-precision”.

Of course, we can’t mention the advantages of plastic, without mentioning the reasons other materials might be better suited for your application. Plastic bearings are generally made from acetal resin rings and nylon cages, which are softer than steel.  Therefore, these bearings are intended for light loads and low speeds.  Additionally, the maximum temperature for the acetal bearings with a nylon cage combination is 100°C. But if you swap both materials for PEEK, this raises the temperature resistance up to 250°C.  

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