POWER TRANSMISSION ELEMENTS AND MECHANISMS 181 

 BEARING BRONZES GROUPED ACCORDING TO FIELDS OF USE 



15 



10 



0) 



10 



15 

 Percent Lead 



20 



25 



30 



In this chart, the lead content and tin content of the alloy is as designated by the coordinates. 

 The percentage of copper content will be 100 minus the total of percentage of tin plus percentage of 

 lead. The numbers in the field of the chart are the Johnson bronze alloy numbers. 



On the preceding page, will be found a table giving both the chemical compositions and physical 

 properties of the alloys whose numbers appear in the field of this chart. 



Refer to the article, Bronze Bearing Alloys — Properties and Applications, Product Engineering, 

 page 202, June, 1934, wherein is set forth the reasons for the various bearing requirements and the 

 effect of each of the various constituents in copper-tin-lead alloys. The characteristics of the 

 10 alloys included in the preceding chart and specific examples of their typical applications are also 

 given. 



Fields of Application of the Five Groups of Bronze Bearing Alloys. — A. This is the most useful 

 range of copper-tin-lead alloys. All alloys in this group have good wear rates and resistance to 

 pounding. Alloy 19 has the highest wear rate and has comparatively good resistance to pounding, 

 but is somewhat brittle. Alloy 27 has a good wear rate and a correspondingly good resistance to 

 pounding, it being moderately tough. 



B. Alloys in this group are suitable for bearing installations only where adequate lubrication 

 can be guaranteed at all times. They have valuable characteristics where exceptionally heavy 

 Impact loads are encountered as in the bearings of crushing machinery. 



C. In this group are the alloys best suited for low loads and moderately high speeds. These 

 alloys are often used as bearing backs. 



D. Alloys in this group are suitable for high speeds and low loads, but should not be used where 

 there is excessive pounding. 



E. AUoys in this group, containing less than 3 per cent tin, are unsuited for general bearing 

 serAace owing to their high wear rate and low resistance to pounding. 



