Worm gears are used for reducing speeds and increasing torque. They are quite compact and can achieve very high speed ratios, often 60:1 or higher. Unfortunately, due to the way they operate, they produce a lot of heat and require special lubrication.
Worm gears and worms contact each other through sliding rather than rolling. This increases friction and thus the operating temperature. Worm gears may operate at close to twice the temperature of other similar gear configurations such as spur gears.
Due to the sliding motion, the worm slowly rubs off the lubricant film while engaging with the worm wheel. The worm surface picks up more lubricant after disengaging, but it is difficult to ensure that it will have a lubricant film that is thick enough to last through the load zone. As a result, worm drives require high viscosity lubricants (due to the high operating temperatures) and have good lubricity to overcome the high-load metal-to-metal contact.
There are four types of lubricants that are commonly used with worm gears: compounded mineral oils, extreme pressure (EP) mineral oils, polyalphaolefin (PAO) lubricants, and polyalkylene glycols (PAG). Compounded, mineral-based oils have natural or synthetic fatty additives that provide good lubricity and better protection against sliding wear. These oils are made from a mineral basestock, containing rust and oxidation inhibitors, and blended with acidless tallow and fatty additives.
Mineral-based, extreme pressure gear oils are often used when no brass components are present. Brass components may react with the sulfur-phosphorous additives found in these oils, although the latest EP oils utilize non-active sulfur to reduce possible corrosion. EP oils are often used for steel gears and when shock loading occurs. PAO gear lubricants have good lubricity properties to help prevent sliding wear. The additives should be checked to make sure that the oil is compatible with the gear material(s).
PAG lubricants are rather new but are becoming more common. They have excellent lubricity, a very high viscosity and are a great choice for low or high temperature operation. Please note that they are not compatible with some mineral oils, seals, and paints.
Worm gears and worms contact each other through sliding rather than rolling. This increases friction and thus the operating temperature. Worm gears may operate at close to twice the temperature of other similar gear configurations such as spur gears.
Due to the sliding motion, the worm slowly rubs off the lubricant film while engaging with the worm wheel. The worm surface picks up more lubricant after disengaging, but it is difficult to ensure that it will have a lubricant film that is thick enough to last through the load zone. As a result, worm drives require high viscosity lubricants (due to the high operating temperatures) and have good lubricity to overcome the high-load metal-to-metal contact.
There are four types of lubricants that are commonly used with worm gears: compounded mineral oils, extreme pressure (EP) mineral oils, polyalphaolefin (PAO) lubricants, and polyalkylene glycols (PAG). Compounded, mineral-based oils have natural or synthetic fatty additives that provide good lubricity and better protection against sliding wear. These oils are made from a mineral basestock, containing rust and oxidation inhibitors, and blended with acidless tallow and fatty additives.
Mineral-based, extreme pressure gear oils are often used when no brass components are present. Brass components may react with the sulfur-phosphorous additives found in these oils, although the latest EP oils utilize non-active sulfur to reduce possible corrosion. EP oils are often used for steel gears and when shock loading occurs. PAO gear lubricants have good lubricity properties to help prevent sliding wear. The additives should be checked to make sure that the oil is compatible with the gear material(s).
PAG lubricants are rather new but are becoming more common. They have excellent lubricity, a very high viscosity and are a great choice for low or high temperature operation. Please note that they are not compatible with some mineral oils, seals, and paints.
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