Understanding the Difference between Cast Bronze Bushings and Oil Impregnated Bronze BushingsSeptember 29, 2020
One type of bearing that is used by a wide variety of industries today is known as a bushing. Bushings are maximised to reduce friction and wear between two surfaces that slide against each other. They are found inside a given hole and often used as a casing for a shaft, pin, or hinge. Machines and equipment that have rotating or sliding shafts often need bushings to improve overall efficiency and reduce vibration, noise, and wear.
Bronze bushings are common nowadays as they can effectively resist shock, impact, wear, and corrosion. These bushings can also be used at high temperatures without getting damaged. Bronze, as a material, can be easily machined, brazed, and soldered, allowing it to be moulded into high-quality bushings. To date, two types of bronze bushings can be used in the industry. These two types are cast bronze bushings and oil impregnated bronze bushings.
Cast Bronze Bushings
Cast bronze bushings are made from a solid or hollow bronze alloy bar stock that undergoes different processes to attain the final shape. This specific bronze alloy is created by continuous or centrifugal casting, which generates a metal with a fine grain structure and strong mechanical properties. The bronze alloy bar stock is then machined through a computer numerical control (CNC) lathe that cuts the cast bar, removes additional bar stock, and processes the finished bushing.
All the processes involved in making cast bronze bushings do not involve any powder, which makes them attain a finer grain structure and greater structural strength. Cast bronze bushings are known to be much stronger, more durable, and more resistant against compressive forces. These features make cast bronze bushings recommended for applications with heavy loads.
One thing to consider, though, is that cast bronze bushings are generally more expensive than others since the whole process of making them can be slow. They also require additional lubrication.
Oil Impregnated Bronze Bushings
Oil impregnated bronze bushings, alternatively, are made by feeding the bronze powder into a die set that is set according to the bushing size. Afterward, the powder particles are pressed tightly together. The bonded powder particles are then placed in a furnace, with its temperature set high enough to effectively join the particles without melting them. The sintering process of metal particles helps them decrease porosity. As for oil impregnated bronze bushings, the final porosity is set at around 25%.
Once the final porosity is maintained, the bronze bushings are then pressed through a set of tools that will provide them the required tolerances. They are ultimately vacuum impregnated that forces oil to their interconnected porosity. Given these processes, oil impregnated bronze bushings can be advantageous due to their lower scrap loss. Manufacturing them at high volumes is also more feasible compared to cast bronze bushings. Also, these bronze bushings do not require any more additional lubrication.
As for the disadvantages, oil impregnated bronze bushings are not great for applications that might react to their impregnated oil. These bushings have also limitations with regards to their mechanical strength.
To know more about these bushings, feel free to contact us at PM Distributors.
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