Why Not to Use Worm Gears
There is one especially glaring reason one would not select a worm gear more than a standard gear: lubrication. The movement between your worm and the wheel equipment faces is completely sliding. There is no rolling component to the tooth get in touch with or conversation. This makes them relatively difficult to lubricate.
The lubricants required are often very high viscosity (ISO 320 and better) and therefore are hard to filter, and the lubricants required are typically specialized in what they perform, requiring a product to be on-site particularly for that type of equipment.
Worm Gear Lubrication
The main problem with a worm gear is how it transfers power. It is a boon and a curse simultaneously. The spiral motion 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 an incredibly 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 (referred to 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 relatively low.
With a worm gear, sliding motion is the only transfer of power. As the worm slides over the tooth of the wheel, it slowly rubs off the lubricant film, until there is absolutely 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 leaves the wheel surface, it accumulates more lubricant, and starts the procedure over again on the next revolution.
The rolling friction on an average gear tooth requires small in the way of lubricant film to complete the spaces and separate the two components. Because sliding takes place on either aspect of the gear tooth apex, a slightly higher viscosity of lubricant than can be strictly needed for rolling wear must overcome that load. The sliding occurs at a relatively low velocity.
The worm on a worm set gear turns, and while turning, it crushes against the strain that’s imposed on the wheel. The only method to avoid the worm from touching the wheel is to have a film thickness large enough never to have the whole tooth surface area wiped off before that portion 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 bigger the strain or temperature, the bigger the viscosity should be), it must have some way to help overcome the sliding condition present.
Read The Right Way to Lubricate Worm Gears for more information on this topic.
Custom Worm Gears
Worm Gears are correct angle drives providing large acceleration ratios on comparatively brief center distances from 1/4” to 11”. When properly installed and lubricated they function as quietist and smoothest working type of gearing. Because of the high ratios possible with worm gearing, optimum speed reduction can 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 huge extent on the helix position of the worm. Multiple thread worms and gears with higher helix position prove 25% to 50% better than single thread worms. The mesh or engagement of worms with worm gears creates a sliding action causing considerable friction and better loss of efficiency beyond other types of gearing. The use of hardened and floor worm swith bronze worm gears boosts efficiency.
LUBRICATION can be an essential factor to improve efficiency in worm gearing. Worm gear action generates considerable high temperature, decreasing efficiency. The quantity of power transmitted at a given temperature raises as the performance of the gearing increases. Proper lubrication enhances effectiveness by reducing friction and temperature.
RATIOS of worm gear sets are dependant on dividing the amount of teeth in the apparatus by the amount of threads. Thus one threads yield higher ratios than multiple threads. All Ever-Power. worm gear models can be found with either still left or right hand threads. Ever-Power. worm equipment sets can be found with Single, Double, Triple and Qua-druple Threads.
Basic safety PROVISION: Worm gearing shouldn’t be used since a locking mechanism to hold large weights where reversing action can cause harm or damage. In applications where potential damage is worm drive shaft non-existent and self-locking is preferred against backward rotation after that use of a single thread worm with a low helix angle immediately locks the worm equipment drive against backward rotation.
Materials recommended for worms can be hardened steel and bronze for worm gears. However, depending on the application unhardened metal worms operate adequately and more economically with cast iron worm gears at 50% horsepower ratings. In addition to metal and hardenedsteel, worms are available in stainless, aluminium, bronze and nylon; worm gears can be found in steel, hardened steel, stainless, light weight aluminum, nylon and nonmetallic (phenolic).
Ever-Power also sells equipment tooth measuring devices 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 recognize all the standard pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, Exterior Involute Splines, Metric Module “MOD”, Stub Tooth, Great Pitches, Coarse Pitches and Unusual Pitches. Refer to the section on GEAR GAGES for catalog amounts when ordering.