Re: Friction Bearings – How Old Is This Term?

Nelson Moyer

I came late to this thread, but the first time ‘friction bearing’ was used related to truck journals was in the March 1956 Model Railroader. ‘Solid bearings’ was first mentioned relative to truck journals in the October 1941 issue of Model Railroader.


Nelson Moyer


From: <> On Behalf Of Clarence Zink
Sent: Tuesday, July 6, 2021 6:21 PM
Subject: Re: [RealSTMFC] Friction Bearings – How Old Is This Term?


As a model railroader professionally employed in the oil & gas, water well, geotechnical, and mineral drilling businesses since 1972, the "friction bearing" has been used in the drill bit field for several decades, and is understood to be a lubricated, sliding contact type bearing.  In the drilling business, the term "friction bearing" is interchangeable with "journal bearing", and represent certain characteristics for durability.  A friction/journal bearing may consist of an internal stationary spindle in direct contact with the external "rolling cone" (which breaks the rock), or it may have a 'bushing' between the rolling cone and spindle.  In any case, metal slides against metal.  It must be lubricated, or the friction will quickly destroy the bearing.  In the drilling business, these types of drill bits are always "sealed", to prevent contamination by drill cuttings, and premature destruction of the bearings.

As opposed to a "roller bearing" type drill bit, which consists of a rolling cone (which breaks the rock), the stationary spindle, and conventional "roller bearings" inserted between the cone and spindle.  In this type of drill bit, the bearing system may or may not be "sealed", depending on the drilling application.  If the roller bearing is sealed, then the drill bit is intended to be used with a drilling fluid to flush cuttings from the hole.  If the roller bearing is not sealed, it is termed either an "open bearing" bit or an "air bearing" bit.  If an "open bearing" type, then the drill bit is intended to be used as a "throw away" type bit with a limited life. with either liquid or non liquid flushing medium.  If it is an "air bearing" bit, it is intended to be used with extremely large quantities of compressed air as the flushing medium, and is intended to be used to destruction.

Drill bits used in the mining, geotechnical, and water well drilling businesses, while carefully designed, engineered, and manufactured, generally have somewhat looser tolerances than bits for oil & gas, and are generally significantly less expensive, because the 'cost of failure' is simply not as high.

Yeah, more than you wanted to know about drill bits.

Best regards,


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