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Plain Bearings VS. Plane Bearingsplain-plane-bearing

There is some disagreement in the engineering community as to whether a plain bearing is the same as a plane bearing.  Is a plane bearing a flat bearing, or can it refer to bearings with round surfaces, like journal bearings?  This article may not establish a firm answer to this question, but it will give food for thought.


The controversy began from the first Bearing Basics post.  Here are other articles on polymer bearings :

A plain bearing, according to Wikipedia (which is not necessarily the most reliable resource but often quite informative), is a bearing surface with no rolling elements [1] , which is a definition that most engineers would agree with.  In essence, the bearing surface itself is smooth.

The Bearing Specialists Association uses the term plane bearing on both their website and in their literature to refer to what others term a plain bearing [2], [3].  However, a search on the American Bearing  Manufacturers Association showed no results for plane bearing, but three results for plain bearing [4].

On the other hand,  many bearing companies use the term plane bearing to refer to both flat bearings and journal bearings, defining a plane bearing as one that operates without rolling elements and explain their choice of the word “plane” as follows :

“The term ‘plane’ comes from geometry; it establishes the plane of operation of the centerline relative to the load.”

Also, a 1933 edition of The Journal of Applied Mechanics includes a paper where a journal bearing is specifically referred to as a plane bearing [5].

There is a special type of bearing called a slide plate bearing which typically has one or more flat surfaces and is used to constrain motion to sliding along a single plane.  Some argue that this flat bearing is a true plane bearing.  However, several industry leaders actually include this in their definition of a plane bearing, alongside journal bearings.

As a final note, one interesting argument against the use of the use of the word “plain” is the challenge to define a “fancy” bearing.


So, is it plane or plain bearings?

It seems the choice remains to the individual, as long as the definition is clear and the term consistently used.

For information on polymer bearings check out the Polymer Bearing Material Comparision Charts Download.


[1] Wikipedia, “Plain Bearing,” [Online]. Available: [Accessed 6 August 2015].
[2] Bearing Specialists Association, “Bearing Specialists Association,” [Online]. Available: [Accessed 5 August 2015].
[3] Educational Services Committee, BSA, “ESC Report: Plane Bearings,” Bearing Specialists Association, Glynn Ellen, Illinois, 1994.
[4] American Bearing Manufacturer’s Association, “American Bearing Manufacturer’s Association,” [Online]. Available: [Accessed 5 August 2015].
[5] American Society of Mechanical Engineers, Applied Mechanics Division, Journal of Applied Mechanics, Vols. 1-4, American Society of Mechanical Engineers, 1933.



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