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Sibro

Oil-soaked sintered bearings

ttv

Sibro
Sibro sintered bearings for maintenance-free operation!

SIBRO sintered bearings offer automatic lubrication over their entire service life thanks to their oil-impregnated structure. They are the perfect choice for applications where high speed and medium loads are required. Ideal for drive technology, paper and textile machines and agricultural machinery - SIBRO ensures smooth operation without maintenance.

Sibro advantages

  • Maintenance-free due to self-lubrication
  • External lubrication possible without any problems
  • Available with solid lubricant MOS2 for applications in vacuum and higher temperatures
  • Very good bearing properties at high speeds and medium loads
  • Wide range of bearings in all conceivable dimensions

Sibro areas of application

  • Drive technology (servomotors and gearboxes)
  • Conveyor technology
  • Paper and textile machines
  • Automotive
  • Agricultural machinery

You can rely on over
40 years of experience

Specializing in the production and manufacture of high-quality plain bearings, slide rails and special parts since 1983.

Overview

Profil Design Base material Load capacity Temperature Range Friction coefficient
SIBRO-FU-1 Sintered bronze CuSn6Zn6Pb3 / CuSn10 35 N/mm2 -80°C to +160°C 0.12 - 0.18
SIBRO-FU-2 Sintered iron Fe 45 N/mm2 -80°C to +160°C 0.15 - 0.20
SIBRO-FU-3 Sintered bronze steel Fe + Cu + C 45 N/mm2 -80°C to +160°C 0.12 - 0.20

Description SIBRO sintered bronze and sintered iron sliding bushings

Sintered bronze bushing SIBRO-FU-1

The SIBRO-FU-1 sliding bushings made from sintered bronze powder are pressed to shape and sintered under a high pressure and temperature. The oil is simultaneously dispensed into the tiny pores on the metal.

The SIBRO-FU-1 sliding bushings can be used in dry conditions for applications with medium speeds and low loads over a long period of time without requiring any maintenance. Sintered bronze sliding bushings are economical options, and are available in an almost unlimited variety of dimensions. They are popular in electrical and electronic machinery, chemical engineering machinery, cars and office equipment.

Sintered bronze bushing SIBRO-FU-2

The SIBRO-FU-2 sintered iron sliding bearings protect the shafts by means of the embedded oil. At low loads, these bearings have the same sliding and frictional properties as the sintered bronze sliding bushings. . The absorbed oil in the sintered iron sliding bushings helps prevent seize-ups.

These bushings are commonly used in textile machinery, power tools and shock absorbers for cars and motor bikes. They can also be used statically as guide bushings or retaining bushings.

Sintered bronze bushing SIBRO-FU-3

The SIBRO-FU-3 sintered bronze steel sliding bushings have the same benefits as the SIBRO-FU-1 and SIBRO-FU-2 bushings.

The proportions of iron and bronze can be configured by the client according to different requirements.

Sintered bronze or sintered iron plain bearings?

Two materials have proven to be particularly suitable for the manufacture of sintered plain bearings: Sintered bronze and sintered iron. Both materials can be processed into high-precision bearing components with an exact pore structure and excellent surface quality - basic prerequisites for reliable lubrication and stable shaft guidance.

 

Sintered bronze 

Sintered bronze is the premium material among sintered bearings and offers impressive properties:

  • Excellent emergency running properties
  • High damping of vibrations and natural oscillations
  • Increased PV load capacity (pressure × speed)
  • Very good corrosion resistance
  • Quiet and reliable operation

These properties make sintered bronze the ideal choice for demanding applications where operational reliability, durability and low noise levels are required.

 

Sintered iron 

Sintered iron offers an economical solution for less complex applications. It is particularly suitable where:

  • the requirements for attenuation and PV value are moderate
  • a favourable price is in the foreground
  • the environment is clean, dry and free from aggressive media

Thanks to its cost efficiency, sintered iron is ideal for series applications with stable operating conditions.

Conclusion: Both materials have their strengths - the right choice depends on the requirements of your application. We would be happy to advise you on selecting the optimum material for your plain bearing solution.

Properties of SIBRO sintered plain bearings

Sintered plain bearings are among the most proven products of powder metallurgy and have been a fixture in a wide range of technical applications for decades. Their performance is largely based on two key properties: the high dimensional accuracy in production and the characteristic pore structure of the material. Both are decisive for the self-lubricating effect - and therefore for reliable, low-maintenance use in numerous plain bearing applications.

How SIBRO sintered plain bearings work

One key factor is crucial for low-friction and wear-free movement within a plain bearing: reliable separation of the moving surfaces using a suitable lubricant. Only when the lubricant is in the right place at the right time and forms a stable lubricating film can the bearing realise its full potential.

The structure of the material plays a decisive role in sintered plain bearings in particular. Thanks to their open-pored microstructure, these bearings have a pore volume of around 15-25 % of the total volume. These pores serve as storage chambers for liquid or solid lubricants, which are released independently onto the sliding surfaces - exactly when they are needed.

The lubricant stored in the pores is transported into the so-called bearing gap by the movement of the shaft. There - due to the slight eccentricity between the shaft and bearing - a wedge-shaped lubrication zone is formed. This geometry leads to a hydrodynamic effect: the lubricating film builds up automatically, without any external feed. The movement of the shaft is sufficient to distribute the lubricant continuously.

The result: a maintenance-free, durable and reliable bearing with excellent emergency running properties - ideal for demanding applications in industry, mechanical engineering or automation.

Service life of SIBRO sintered plain bearings

The service life of a sintered plain bearing depends largely on the operating conditions and the lubricant supply. Under optimum conditions - i.e. at constant speed in continuous operation and with a stable hydrodynamic lubricating film and room temperature - running times of over 100,000 hours can be achieved. The prerequisite for this is a sufficient quantity of oil in the bearing, which is provided by the open-pored structure of the sintered material.

The centrepiece of a self-lubricating sintered plain bearing is its finely interconnected pore space. It accounts for around 15-25 % of the total volume and serves as a reservoir for liquid or solid lubricants. These are continuously released onto the sliding surface and keep the lubricating film stable even during long periods of operation - without any external lubricant supply.

As long as this lubricating film remains intact, there is no direct contact between the shaft and bearing - wear is therefore virtually eliminated. In practice, however, certain conditions such as high temperatures, vibrations, contamination or an uneven load can affect the service life. Oil losses due to evaporation, decomposition or leakage must also be taken into account in the design.

Special materials are used for more demanding environments: sintered bronzes containing MoS₂, for example, are designed for continuous operation up to 300 °C (even up to 400 °C for short periods) and offer a high level of operational reliability even under extreme conditions.

Conclusion: Sintered plain bearings are durable, maintenance-free and highly resilient design elements. The right design, the right material and a lubrication strategy tailored to the application form the basis for maximum service life - even under difficult conditions.

Bearing surface and mating materials (shaft)

In order for a sintered plain bearing to realise its full potential, the selection of the right shaft material - i.e. the so-called mating partner - plays a central role. It is not only the hardness and material properties that are decisive, but also the surface quality and geometric precision.

Recommended materials for shafts and journals

High-strength steels with a tensile strength of at least 600 N/mm² and hardened steels from 55 HRC are ideal. Under certain operating conditions, unhardened, stainless, chrome-plated or nickel-plated materials can also be used. However, caution is advised with galvanised surfaces: Excessively smooth or non-adhesive coatings - as with galvanised shafts - can hinder lubricant distribution or clog the pore structure of the bearing

Surface quality - the key to longevity

The lubricating film on sintered plain bearings is particularly thin. This makes a finely machined shaft surface with a roughness of Ra ≤ 0.8 µm all the more important. Smooth and load-bearing surfaces can be achieved using processes such as superfinishing, lapping, roller burnishing or vibratory grinding. A surface that is too rough or irregular, on the other hand, can damage the bearing and significantly impair its self-lubricating properties.

Corrosion protection and special environments

In humid or aggressive environments, we recommend hard chrome-plated shafts or alternatively stainless materials - supplemented by molybdenum disulphide coatings or chrome-plating to further improve the sliding properties. Roller burnishing or hard chrome plating of the surface is particularly useful for stainless steels in order to minimise the abrasive effect of nickel.

Geometry - precise shape instead of compromise

Not only the surface, but also the shape of the shaft is crucial. Major deviations from the ideal circular or cylindrical shape can lead to pumping effects that cause oil loss and noise. We therefore recommend keeping shape tolerances as low as possible.

For dusty or contaminated areas of application, the bearing point should also be protected by axial seals to prevent the ingress of particles and to ensure long-term functional reliability.

 

Coefficient of friction SIBRO sintered plain bearing

The coefficient of friction depends on many factors, including the surface quality of the mating material, the circumferential speed and the bearing temperature. If
If these factors are taken into account, the following values can be calculated:

Oil-impregnated bearings: 0.05 - 0.10
Dry lubricated bearings: 0.15 - 0.25

A lower friction coefficient for oil-impregnated bearings can be achieved by low load and high sliding speed. 

Assembly of SIBRO sintered plain bearings

Our sintered plain bearings are high-precision design elements that are manufactured to exact dimensions and optimised for their installation situation. The H7/r7 fit has proven itself for the housing seat - it ensures a secure hold and reliable function during operation.

Professional press-fitting for precise results

We recommend the use of a press-fit mandrel to ensure the dimensional accuracy and surface quality of the bearings in the long term. This should be at least three times as long as the bearing itself and should be hardened and ground. Ground and lapped carbide mandrels are particularly suitable for series mounting.

Alternative mounting methods for special applications

In addition to classic press-fitting, there are also other mounting techniques available depending on the requirements, including

  • Paste
  • Pouring
  • Injecting
  • Vulcanising 
  • Flanging (e.g. for bearing made of sintered bronze)

These methods are particularly suitable for special materials or operating conditions - we will be happy to advise you on the selection of the optimum solution.

Special dimensions can be realised flexibly

Thanks to our extensive stock of tools, we can also realise special dimensions and individual tolerances at short notice. We manufacture small batches flexibly by machining. For larger quantities, we develop customised tools so that the unit costs are on a par with standard components. Pro rata tool costs are only incurred if no suitable tool is available.

Conclusion: Whether standard or customised - our sintered plain bearings impress with maximum precision, simple assembly and economic scalability.

Bearing SIBRO sintered plain bearing

In order for our self-lubricating sintered plain bearings to perform to their full potential, proper bearing support is crucial. These bearings contain approx. 25 per cent oil by volume, which contributes significantly to their reliable function.

Important for storage

Avoid storage conditions in which the oil can escape - for example by placing it on absorbent materials such as wood, paper or cardboard. These extract oil from the bearing, which can lead to a loss of function in the long term.

Our recommendation

Leave the bearings in the original plastic packaging until installation. These not only protect against oil loss, but also reliably protect against dust, dirt and other contaminants that could impair operation.

However, if oil leaks do occur, the bearings must be re-impregnated. This is because heat build-up can only be prevented and a long service life of the bearing guaranteed if there is sufficient lubricant.

Download technical informations

Technical information SIBRO-FU-1/2/3

Product catalogue

Technical information


Your expert for sintered bronze sliding bushings and sintered iron sliding bushings
Harald Nitzschke
E-Mail: nitzschke@ttv-gmbh.de
Your direct contact to us.
Do you have any questions? Do you need help? Then feel free to give us a call. Would you like a quote? Please send us the details via the form.
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Frequently asked questions

Do SIBRO sintered bearings need to be lubricated regularly - or not at all?

No, relubrication is not necessary - as long as the sintered bearing works under the correct operating conditions.

SIBRO sintered bearings are impregnated at the factory with approx. 25 % oil by volume. The oil sits in the open pores of the sintered metal and thus ensures automatic lubrication: Friction during operation increases the temperature and pressure in the sintered bearing, forcing the oil out of the pores towards the sliding surface. As soon as the movement stops, the oil is then drawn back into the sintered bearing (capillary effect).

Prerequisites:

  • Load and speed are within the permissible range (PV value).
  • The ambient temperature remains below 160 °C.
  • No permanent dry running under load.

In special cases - e.g. with vacuum, very high speeds, a high continuous thermal load or aggressive media - it may make sense to additionally lubricate the sintered bearing or to switch to a variant with solid lubricant (e.g. MoS₂).

For typical applications such as:

  • Electric motors,
  • transmission technology
  • textile machines
  • or agricultural machinery

factory lubrication is usually sufficient. Once the sintered bearing has been correctly installed, it runs maintenance-free and without relubrication.

When does it make sense to use sintered iron or sintered bronze steel instead of sintered bronze for plain bearings?

When the sintered bearing has to be very robust or corrosion-resistant.

You can do little wrong with plain bearings made of sintered bronze (FU-1): they have good sliding properties, are maintenance-free and economical. This is sufficient for many applications - especially for medium loads and clean running.

Plain bearings made of sintered iron (FU-2) are of interest when

- the bearing point is subject to high mechanical loads

- a high load capacity is required and the running does not have to be extremely fine

- the sintered bearing is used, for example, in power tools, shock absorbers or machines with constant vibration.

Bearings made of sintered bronze steel (FU-3) make sense when you need both:

  • high load capacity and
  • better sliding properties due to the bronze content.

The advantage of FU-3 is that you can have the ratio of iron, bronze and carbon adjusted to your application. This is particularly worthwhile for series applications or extreme operating conditions.

Summarized for you at a glance:

  • FU-1 = standard is inexpensive and glides well under medium loads.
  • FU-2 = more robust for higher loads, but somewhat rougher running.
  • FU-3 = adaptable is a compromise between the two, and can be individually adjusted.

If you are not sure, a look at the speed, load and environment is usually enough. Or you can give us the application data and we will tell you which type suits your application.Kontakt

Is there a difference between SIBRO and the FU plain bearings from the technical catalog?

Technically, SIBRO bearings and the FU types from the technical catalog are identical.

At TTV, SIBRO is the product name for oil-impregnated sintered bearings. However, these are the same materials, the same manufacturing processes and the same type designations as in the catalog:

  • SIBRO-FU-1 = sintered bronze (CuSn6Zn6Pb3 or CuSn10)
  • SIBRO-FU-2 = sintered iron (Fe)
  • SIBRO-FU-3 = Sintered bronze steel (Fe + Cu + C)

What happens if my bearing operates above the maximum recommended temperature?

Then the self-lubrication no longer works. The bearing wears out more quickly and may even fail completely.

SIBRO bearings are designed for temperatures up to 160 °C in continuous operation. The limit value is not a rough guide value, it is technically justified: The oil in the pores begins to evaporate or chemically decompose at approx. 160 °C. Once this happens, the automatic lubrication system no longer works.

This has two direct consequences:

  1. too little lubrication → increasing friction → more heat → even faster degradation.
  2. dirt or abrasion sticks to the dry sliding surface → increased material removal.

This means that the bearing can still hold up mechanically for a while, but wear increases exponentially. In practice, you often only notice this when the shaft is already damaged or bearing parts have run in.

For higher temperatures (above 160 °C), you therefore need either

  •                 a plain bearing with solid lubricant such as MoS₂, which has no volatile oil content
  •                 or impregnate the bearing with a special temperature-stable oil.

This is not necessary for typical applications in mechanical engineering, automotive engineering or the textile industry, where the temperature usually remains well below the critical temperature of 160° Celsius.

Can I also press the bearings into plastic or other materials?

Yes, but only under certain conditions - and not if the bearing is already oiled.

In principle, SIBRO bearings can also be mounted in plastic, aluminum or other non-ferrous materials. But not after impregnation. The oil in the pores would escape when pressed in, would not be compatible with the material or would interfere with the connection during bonding.

This is the correct procedure:

  • Install the sintered bearing in a dry state (i.e. before impregnation), glue, inject or cast in.
  • Then impregnate the bearing afterwards, e.g. by immersing it in oil at 70-90 °C for several hours.

By the way: If you machine the bearing, e.g. calibrate, turn or coat it, you must follow the same procedure: first machine, then oil.

For which mechanical engineering applications are plain bearings made of sintered bronze and sintered iron particularly suitable?

Anywhere where you do not have access to the bearing point or where you do not want anyone to relubricate later.

Plain bearings made of sintered bronze and sintered iron are maintenance-free, oil-impregnated and robust. This makes them ideal for machines where downtime is expensive or a lubrication point is difficult or impossible to access.

Sintered bearings are often used here:

  • Drive technology
    z. e.g. servomotors, gearbox bushes and conveyor rollers
  • Textile and paper machines
    with high speeds, cyclical operation and no time for relubrication
  • Agricultural machinery
    Bearing points in outdoor areas with heavy dirt ingress and irregular operation
  • Automotive
    z. e.g. damper bearings, pedal mechanisms and clutch actuators
  • Power tools
    Small installation spaces, plain bearings work under high temperatures and continuous loads

Not sure which plain bearing is right for your application?

Tell us what the plain bearing needs to do. And we'll tell you what works for you.

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