Angle Grinder gear lubrication-Case Study

Like most power tools, commercial grinders operate at high speeds with considerable amounts of applied pressure. If not addressed in the design stage, these two factors can lead to premature product failure.

A grease is required to extend the life of the angle grinder by protecting the gears in the gearbox from premature wear.


As the angle grinder will be produced in large volumes there is a commercial pressure to keep the lubricant cost as low as possible. The chosen lubricant will have to protect the gears from heavy loading during routine operation. Constant start/stop operations and periods of extended use present extra wear prevention challenges for the lubricant. The chosen product also needs to operate in a wide temperature range as the grinder wheel turns speeds of 6,500 to 8,500 rotations per minute, generating significant extra heat.

Proposed Solution

  • A very soft grease to ensure sufficient ‘wetting’ of the gears.
  • Ester is the preferred base oil for metal on metal gears but a grease with an Ester and Polyalphaolefin (PAO) blend is chosen to lower the cost.
  • The base oil blend is thickened with Lithium Soap.
  • Extreme Pressure (EP) and Rust Inhibitor additives are included in the formula of the grease to enhance the product performance.
  • A grease with high levels of oil separation is desirable for effective lubrication in this this high speed application.

Product Selection

Rheolube 380-G1

Initially Rheolube 380 was proposed but a softer version of the 380 was created called Rheolube 380-G1; it was found that a grease containing a higher percentage of the PAO/Ester base oil proved advantageous in sufficiently extending the life of the gear train.


After performance and functional life testing by the customer, they decided the Rheolube 380-G1 grease had the right performance-price balance and provided the required return on investment, leading to longer term savings due to fewer product failures and considerably lower levels of warranty claims.

Rheolube 380-G1 use resulted in improved device reliability and lower levels of warranty claims.

Please get in contact with us if you are interested to find out how we can improve your power tool performance and/or functional life.

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