Gear backlash in precision applications is a critical element of gear system performance. Too much backlash can result in inefficiencies of motion in the gear train and will ultimately damage a gear’s teeth. Too little can mean the gears bind up and cause excessive wear to the tooth’s surface and the root of the gear, or even the fracturing of a tooth. Establishing and setting the appropriate amount of backlash is essential in gear design and manufacturing, according to Berg, a Regal Rexnord Brand.

What Is Backlash in Gears?

Gear backlash is a mechanical engineering term referring to the lost motion resulting from spaces occurring between gear teeth during the mesh process of bidirectional gears. Backlash is seen in the mating gears at the pitch circle diameter. In motors, it is a specification used to indicate mechanical precision of a transmission component between the power plant and the load of a gear train. In common usage, the term can refer to the spaces themselves or the loss of motion resulting from the spaces when a gear direction is reversed.

In other words, backlash can be defined as the excess wideness of a space between teeth of one gear compared to the thickness of the tooth of its mating gear. Both the resulting gap and wasted motion occurring when the gap is closed can be considered backlash.

While some gaps are required between mating gear parts to prevent jamming and promote proper lubrication, excessive gaps can add unexpected load forces, creating slippage between teeth, gear wear and eventual failure of entire gear systems.

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