Why Not to Use Worm Gears
There is one particularly glaring reason why one would not choose a worm gear more than a typical gear: lubrication. The movement between the worm and the wheel gear faces is completely sliding. There is absolutely no rolling component to the tooth contact or conversation. This makes them relatively difficult to lubricate.
The lubricants required are usually high viscosity (ISO 320 and greater) and therefore are difficult to filter, and the lubricants required are typically specialized in what they do, requiring a product to be on-site particularly for that kind of equipment.
Worm Gear Lubrication
The primary problem with a worm gear is how it transfers power. It is a boon and a curse simultaneously. The spiral movement allows huge amounts of reduction in a comparatively small amount of space for what’s required if a standard helical equipment were used.
This spiral motion also causes a remarkably problematic condition to be the primary mode of power transfer. That is commonly known as sliding friction or sliding put on.
With an average gear set the power is transferred at the peak load point on the tooth (known as the apex or pitchline), at least in a rolling wear condition. Sliding takes place on either side of the apex, however the velocity is fairly low.
With a worm gear, sliding motion is the only transfer of power. As the worm slides across the tooth of the wheel, it gradually rubs off the lubricant film, until there is no lubricant film remaining, and as a result, the worm rubs at the metallic of the wheel in a boundary lubrication regime. When the worm surface area leaves the wheel surface, it accumulates more lubricant, and starts the process over again on the next revolution.
The rolling friction on a typical gear tooth requires little in the way of lubricant film to fill in the spaces and separate the two components. Because sliding happens on either part of the apparatus tooth apex, a slightly higher viscosity of lubricant than is usually strictly needed for rolling wear must overcome that load. The sliding occurs at a comparatively low velocity.
The worm on a worm set gear turns, even though turning, it crushes against the strain that is imposed on the wheel. The only way to avoid the worm from touching the wheel is certainly to possess a film thickness large enough to not have the entire tooth surface wiped off before that part of the worm has gone out of the load zone.
This scenario requires a special sort of lubricant. Not only will it will have to be a relatively high viscosity lubricant (and the higher the load or temperature, the higher the viscosity should be), it must have some way to greatly help conquer the sliding condition present.
Read The Right Way to Lubricate Worm Gears to learn more on this topic.
Custom Worm Gears
Worm Gears are right angle drives providing large speed ratios on comparatively short center distances from 1/4” to 11”. When correctly mounted and lubricated they function as the quietist and smoothest working type of gearing. Due to the high ratios possible with worm gearing, optimum speed reduction could be accomplished in less space than a great many other types of gearing. Worm and worm gears operate on nonintersecting shafts at 90° angles.
EFFICIENCY of worm gear drives depends to a big extent on the helix angle of the worm. Multiple thread worms and gears with higher helix angle prove 25% to 50% more efficient than worm drive shaft solitary thread worms. The mesh or engagement of worms with worm gears creates a sliding action causing considerable friction and better lack of efficiency beyond other styles of gearing. The usage of hardened and ground worm swith bronze worm gears raises efficiency.
LUBRICATION can be an essential factor to boost performance in worm gearing. Worm gear action generates considerable heat, decreasing efficiency. The quantity of power transmitted at confirmed temperature boosts as the effectiveness of the gearing improves. Proper lubrication enhances efficiency by reducing friction and high temperature.
RATIOS of worm equipment sets are determined by dividing the number of teeth in the gear by the amount of threads. Thus single threads yield higher ratios than multiple threads. All Ever-Power. worm gear sets are available with either still left or right hand threads. Ever-Power. worm gear sets are offered with Single, Double, Triple and Qua-druple Threads.
Protection PROVISION: Worm gearing should not be used since a locking mechanism to hold large weights where reversing actions could cause harm or injury. In applications where potential damage is nonexistent and self-locking is desired against backward rotation after that use of an individual thread worm with a minimal helix angle instantly locks the worm gear drive against backward rotation.
MATERIAL recommended for worms is definitely hardened steel and bronze for worm gears. Nevertheless, depending on the application unhardened steel worms operate adequately and more economically with cast iron worm gears at 50% horsepower ratings. In addition to steel and hardenedsteel, worms are available in stainless, aluminum, bronze and nylon; worm gears can be found in steel, hardened metal, stainless, aluminium, nylon and non-metallic (phenolic).
Ever-Power also sells equipment tooth measuring gadgets called Ever-Power! Gear Gages reduce mistakes, save money and time when identifying and ordering gears. These pitch templates are available in nine sets to identify all the standard pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, External Involute Splines, Metric Module “MOD”, Stub Tooth, Good Pitches, Coarse Pitches and Unusual Pitches. Refer to the section on GEAR GAGES for catalog figures when ordering.
Why Not to Use Worm Gears