Why Not to Use Worm Gears
There is one particularly glaring reason why one would not select a worm gear more than a standard 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 interaction. This makes them relatively difficult to lubricate.
The lubricants required are often very high viscosity (ISO 320 and better) and therefore are difficult to filter, and the lubricants required are typically specialized in what they perform, requiring something to be on-site specifically for that kind of equipment.
Worm Gear Lubrication
The main problem with a worm gear is how it transfers power. It really is a boon and a curse at the same time. The spiral movement allows large sums of reduction in a comparatively small amount of space for what’s required if a standard helical gear were used.
This spiral motion also causes a remarkably problematic condition to be the primary mode of power transfer. This is commonly known as sliding friction or sliding wear.
With an average gear set the worm drive shaft energy 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 may be the only transfer of power. As the worm slides across the tooth of the wheel, it slowly rubs off the lubricant film, until there is no lubricant film left, and for that reason, the worm rubs at the metal of the wheel in a boundary lubrication regime. When the worm surface leaves the wheel surface area, it picks up more lubricant, and begins the procedure over again on another revolution.
The rolling friction on an average gear tooth requires little in the way of lubricant film to complete the spaces and separate both components. Because sliding takes place on either side of the apparatus tooth apex, a slightly higher viscosity of lubricant than can be strictly needed for rolling wear is required to overcome that load. The sliding takes place at a relatively low velocity.
The worm on a worm set gear turns, even though turning, it crushes against the load that is imposed on the wheel. The only way to prevent the worm from touching the wheel is usually to have a film thickness huge enough to not have the whole tooth surface wiped off before that portion of the worm is out of the load zone.
This scenario requires a special kind of lubricant. Not just will it will have to be a comparatively high viscosity lubricant (and the bigger the load or temperature, the higher the viscosity should be), it must have some way to help conquer the sliding condition present.
Read The Right Method to Lubricate Worm Gears to find out more on this topic.
Custom Worm Gears
Worm Gears are right angle drives providing large quickness 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. Because of the high ratios possible with worm gearing, maximum speed reduction could be accomplished in less space than many other types of gearing. Worm and worm gears operate on nonintersecting shafts at 90° angles.
EFFICIENCY of worm equipment drives depends to a sizable degree 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 produces a sliding action causing considerable friction and better lack of efficiency beyond other types of gearing. The use of hardened and ground worm swith bronze worm gears boosts efficiency.
LUBRICATION is an essential factor to improve performance in worm gearing. Worm gear action generates considerable heat, decreasing efficiency. The quantity of power transmitted at a given temperature boosts as the effectiveness of the gearing boosts. Proper lubrication enhances performance by reducing friction and warmth.
RATIOS of worm gear sets are determined by dividing the number of teeth in the gear by the number of threads. Thus solitary threads yield higher ratios than multiple threads. All Ever-Power. worm gear models can be found with either remaining or right hand threads. Ever-Power. worm gear sets are offered with Single, Dual, Triple and Qua-druple Threads.
Security PROVISION: Worm gearing shouldn’t be used since a locking mechanism to hold weighty weights where reversing actions can cause harm or injury. In applications where potential damage is non-existent and self-locking is desired against backward rotation after that use of a single thread worm with a low helix angle instantly locks the worm gear drive against backward rotation.
Materials recommended for worms is usually 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 are available in steel, hardened metal, stainless, aluminum, nylon and non-metallic (phenolic).
Ever-Power also sells equipment tooth measuring devices called Ever-Power! Gear Gages decrease mistakes, save money and time when identifying and ordering gears. These pitch templates can be found in nine sets to identify all the regular pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, External Involute Splines, Metric Module “MOD”, Stub Tooth, Fine Pitches, Coarse Pitches and Unusual Pitches. Make reference to the section on GEAR GAGES for catalog numbers when ordering.
Why Not to Use Worm Gears