Understanding Bronze Bushes.

Cast bronze vs. Oilite bronze. What is the difference? 

 


Cast Bronze - including: 

Phosphor bronze – phosphor is added to improve casting properties.

Leaded bronze -  lead is added to improve machining properties and for higher speed applications.)

Oilite sintered bronze




Speed 

Depending on material max shaft speed 1.25 to 5m/s 

(non leaded bronzes, up to approx 2.5m/s)

 

6 m/s

Shock loading

Generally well suited to shock loading.

 

Only suitable for application with low shock loading.

Operating environment

Can be used in dirty/dusty environments (depending on environment)

 

Operate best in clean, low dust environments.

Availability

Very limited stocks available I the UK. Typically bushings are machined to order.

 

Over 1000 sizes available in stock in the UK, in Metric and imperial sizes.

Cost

Bearing costs often high due to small production runs. Cheaper than sintered when bought in bar or plate form.

Around 20% less bronze than cast due to porosity. 

Mass production and sintering process keeps manufacturing cost down.

 

ROHS compliance

Leaded cast bronzes are not ROHS compliant.

Yes

 

Lubrication

Additional lubrication required, oil or grease.

Self lubricating. Oil is contained within the bearing and released as shaft rotates

 

Maximum load

Between 17 and 55 N/mm2

(Leaded bronzes have generally lower max loads)

Approx 14N/mm2

Phosphor bronze or Oilite?


There is a common misconception that Oilite is made from phosphor bronze. Even some re-sellers of oilite refer to it as sintered phosphor bronze. 

Phosphor is generally added to make molten bronze flow better when casting, Oilite is made from tin bronze without the phosphor additive as its addition would not assist in the sintering process.


 

Manganese Bronze and Oilite sintered bronze, what is the link?

 

Another material commonly confused with Oilite is manganese bronze, not due to appearance, or similar applications, rather because the company who used to make Oilite was called Manganese Bronze: 

From the 1930s Oilite was manufactured in the UK by Manganese Bronze. This only changed in 2003 when the sintering division was sold off.


 The material; manganese bronze, is actually a brass (copper and zinc alloy), hardened with manganese. 


Bizarrely Manganese Bronze Holdings PLC who once made Oilite is now best known for making the iconic London Taxis.


Brass bearing or Bronze bearing?

Bronze bushings are often referred to as Brass bearings. In reality, bearings are rarely made from Brass (copper and zinc alloys). Brass is highly malleable and generally has a lighter, more golden colour and is used in door furniture, and musical instruments. Bronzes, (copper and tin alloys) are generally a darker colour and have better bearing properties (they are, on the whole, both stronger and have lower coefficients of friction).

In reality the important question is more often: What grade or bronze?, rather than , is it brass or bronze?