Why Not to Use Worm Gears
There is one especially glaring reason why one would not select a worm gear more than a typical gear: lubrication. The movement between the worm and the wheel gear faces is entirely sliding. There is absolutely no rolling element of the tooth get in touch with or interaction. This makes them relatively difficult to lubricate.
The lubricants required are usually very high viscosity (ISO 320 and higher) and therefore are tough to filter, and the lubricants required are typically specialized in what they perform, requiring something 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 at the same time. The spiral movement allows large sums of decrease in a comparatively little bit of space for what is 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 wear.
With a typical gear set the energy is transferred at the peak load stage on the tooth (known as the apex or pitchline), at least in a rolling wear condition. Sliding happens on either aspect of the apex, but the velocity is fairly 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 left, and as a result, the worm rubs at the metal of the wheel in a boundary lubrication regime. When the worm surface area leaves the wheel surface, it accumulates more lubricant, and starts the procedure over again on another revolution.
The rolling friction on an average gear tooth requires small in the way of lubricant film to fill in the spaces and separate both components. Because sliding happens on either aspect of the gear tooth apex, a slightly higher viscosity of lubricant than can be strictly necessary for rolling wear is required to overcome that load. The sliding happens at a comparatively low velocity.
The worm on a worm set gear turns, and while turning, it crushes against the strain that is imposed on the wheel. The only way to prevent the worm from touching the wheel is usually to possess a film thickness large enough to not have the entire tooth surface area wiped off before that section of the worm is out of the strain zone.
This scenario requires a special kind of lubricant. Not only will it should be a relatively high viscosity lubricant (and the bigger the strain or temperature, the bigger the viscosity must be), it will need to have some way to greatly help overcome the sliding condition present.
Read The Right Method to Lubricate Worm Gears for more information on this topic.
Custom Worm Gears
Worm Gears are right angle drives providing large velocity ratios on comparatively short center distances from 1/4” to 11”. When correctly installed and lubricated they function as the quietist and smoothest working type of gearing. Because of the high ratios feasible with worm gearing, maximum speed reduction can be accomplished in much less space than many other types of gearing. Worm and worm gears operate on non-intersecting shafts at 90° angles.
EFFICIENCY of worm equipment 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% more efficient than one thread worms. The mesh or engagement of worms with worm gears produces a sliding action leading to considerable friction and higher lack of efficiency beyond other styles of gearing. The use of hardened and floor worm swith bronze worm gears increases efficiency.
LUBRICATION can be an essential factor to improve performance in worm gearing. Worm equipment action generates considerable heat, decreasing efficiency. The amount of power transmitted at a given temperature improves as the performance of the gearing boosts. Proper lubrication enhances performance by reducing friction and high temperature.
RATIOS of worm gear sets are worm drive shaft 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 models can be found with either still left or right hands threads. Ever-Power. worm gear sets can be found with Single, Double, Triple and Qua-druple Threads.
Basic safety PROVISION: Worm gearing shouldn’t be used because 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 preferred against backward rotation then use of an individual thread worm with a low helix angle instantly locks the worm equipment drive against backward rotation.
MATERIAL recommended for worms can be hardened steel and bronze for worm gears. However, depending on the application form unhardened steel worms operate adequately and more economically with cast iron worm gears at 50% horsepower ratings. Furthermore to metal and hardenedsteel, worms can be found in stainless, light weight aluminum, bronze and nylon; worm gears can be found in steel, hardened steel, stainless, light weight aluminum, nylon and non-metallic (phenolic).
Ever-Power also sells gear tooth measuring devices called Ever-Power! Gear Gages decrease mistakes, save money and time when identifying and buying gears. These pitch templates are available in nine sets to identify all the standard pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, Exterior Involute Splines, Metric Module “MOD”, Stub Tooth, Good Pitches, Coarse Pitches and Unusual Pitches. Refer to the section on Equipment GAGES for catalog numbers when ordering.
Why Not to Use Worm Gears