Avoiding Common Gearbox Lubrication Problems

The right-angle worm gearbox is a simple device that is used widely in manufacturing facilities. Like nearly all gears, enclosed worm gear drives require proper lubrication in the appropriate amounts. It is these two factors — lack of lubrication and the use of incorrect lubrication — that are the most common causes of premature failures in worm gearboxes.

Lack of Lubrication

Operating a worm gearbox dry (without lubrication) frequently leads to failure of the unit. Manufacturers often ship gearboxes dry for a couple of reasons. First, the added weight of the lubricant adds to shipping costs, and that weight can be significant in larger gearboxes. Secondly, numerous manufacturing facilities have standardized on a specific lubrication supplier, and while many lubricants are interchangeable, they should not be mixed. Shipping a unit dry allows the end users to ensure commonality within their facility.
Unfortunately, a novice installer may ignore or neglect to read the tags, labels and installation manual warnings that indicate there is no lubrication and start up a drivetrain with a gearbox that is without lubrication. Running a unit dry will rapidly cause damage to the bronze worm gear. Even if lubrication is added after the fact, this damage is permanent, and the gearbox will need to be replaced or rebuilt. There is no way to “heal” a damaged gear.

A gearbox mounted in the worm-under
orientation requires additional lubrication.

Not Enough Lubricant

A related failure occurs when there is too little lubrication. This can often be the result of the gearbox mounting. The most common mounting for a worm gearbox is referred to as “worm over,” which means the worm rests above the bronze gear. In worm-over orientation, a gearbox needs a set level of lubricant. However, this same gearbox assembly can be mounted in the worm-under orientation, which requires additional lubrication.
The gearbox construction and the manner in which lubrication moves with the gears can be such that a unit with worm-under mounting may require as much as 50 percent more lubrication than a unit with worm-over mounting. Failure to increase the amount of lubrication will mean that the bearings on the output shaft will run dry and fail in a relatively short period of time.
For any given gearbox, there is no physical reason a unit may not be mounted in the worm-over or worm-under orientation so long as proper lubrication levels are maintained. One of the problems that results from insufficient lubrication is that failure is not immediate. The unit will perform well for a time, perhaps a few weeks or a month, depending upon the application. As a result, a technician may not make the connection between too little lubricant and the unit failure, and may repeat the error.
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