How to Keep Your Gears Turning, Productively – Part II

This is the second post of a two-part tip series that looks at gears, how they work, and how to optimize their performance through best-in-class lubrication.

Our first post covered different types of gears. This tip will focus on gear motions and lubrication best practices.


Gear Motions

As gears rotate, there are two main types of motion:

Sliding and rolling motion: In gears with where the shafts of the driver and the driven are parallel, sliding and rolling motion exist. In parallel aligned gears, sliding motion exists going into and out of full mesh, and rolling motion exists at mesh. This impacts spur, helical, double helical, and herringbone gears. There is predominant sliding in straight bevel gears, but rolling does exist briefly at full mesh.

Sliding motion only: In gears that are at a right angle to each other and have a curved face, sliding motion predominates. Worm gears are impacted by sliding motion exclusively, while sliding with some rolling affects spiral bevel and hypoid gearing.


Lubrication best practices

Gears may be lubricated by either rust and oxidation inhibited oils, or extreme pressure fortified lubricants. The type of oil to use depends on the gears selected, application and the environment in which it operates.

Rust and Oxidation inhibited oils: These oils may be used in all types of gears. Their application includes gearing that carries low to moderate loads without impact or shock loading. Typical R&O oils used to lubricate gears include AGMA 2 to 8 referring to ISO grades 68 - 680. Example of R&O-lubricated applications would include gear drives on a paper machine or a connecting gear on a compressor or turbine.

Gear or Extreme Pressure fortified oils: These oils are recommended when the gears are heavily loaded and there is the presence or chance of shock loading. Extreme pressure agents are polar compounds that bond to the gear surface to help prevent metal-to-metal contact. The amount and type of extreme pressure agent used depends on the gear design, loading and environment. Typical gear oils include AGMA 2 EP to 8 EP referring to ISO grades 68 - 680. Gear applications that require EP additives would be located in a cement mill or on mobile equipment, to name a few examples.

There are additional grades and classifications for gear oils provided by the AGMA, but for the purposes of this tip, the use of AGMA 2 through 8 and 2EP through 8 EP is sufficient.

Hopefully this tip series on gears was helpful. If you have any questions, let us know in the comments section below!