Why Not to Use Worm Gears
There is one particularly glaring reason one would not select a worm gear over a typical gear: lubrication. The movement between your worm and the wheel gear faces is entirely sliding. There is no rolling component to the tooth contact or interaction. This makes them relatively difficult to lubricate.
The lubricants required are often high viscosity (ISO 320 and greater) and thus are hard to filter, and the lubricants required are usually specialized in what they do, requiring something to be on-site particularly for that kind 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 movement allows large sums of reduction in a comparatively small amount of space for what is 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 a typical 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 occurs on either part of the apex, but the velocity is fairly 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 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 picks up more lubricant, and begins 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 side of the gear tooth apex, a slightly higher viscosity of lubricant than is strictly needed 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’s imposed on the wheel. The only method to avoid the worm from touching the wheel is usually to have a film thickness huge enough never to have the whole tooth surface wiped off before that portion of the worm has gone out of the strain zone.
This scenario requires a special sort 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 must be), it will need to 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 right angle drives providing large rate ratios on comparatively short center distances from 1/4” to 11”. When properly mounted and lubricated they function as quietist and smoothest operating type of gearing. Due to the high ratios feasible with worm gearing, optimum speed reduction can be accomplished in much less space than a great many other types of gearing. Worm and worm gears operate on nonintersecting shafts at 90° angles.
EFFICIENCY of worm worm drive shaft equipment drives depends to a huge degree on the helix angle of the worm. Multiple thread worms and gears with higher helix position prove 25% to 50% better than one thread worms. The mesh or engagement of worms with worm gears produces a sliding action causing considerable friction and greater loss of efficiency beyond other types of gearing. The use of hardened and surface worm swith bronze worm gears boosts efficiency.
LUBRICATION is an essential factor to improve performance in worm gearing. Worm equipment action generates considerable heat, decreasing efficiency. The quantity of power transmitted at confirmed temperature increases as the efficiency of the gearing increases. Proper lubrication enhances efficiency by reducing friction and temperature.
RATIOS of worm gear sets are determined by dividing the number of teeth in the gear by the number of threads. Thus one threads yield higher ratios than multiple threads. All Ever-Power. worm gear sets can be found with either still left or right hand threads. Ever-Power. worm gear sets can be found with Single, Dual, Triple and Qua-druple Threads.
Basic safety PROVISION: Worm gearing shouldn’t be used since a locking mechanism to carry weighty weights where reversing action could cause harm or injury. In applications where potential harm is non-existent and self-locking is preferred against backward rotation after that use of an individual thread worm with a minimal helix angle automatically locks the worm gear drive against backward rotation.
MATERIAL recommended for worms is certainly hardened steel and bronze for worm gears. Nevertheless, 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, 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 devices called Ever-Power! Gear Gages reduce mistakes, save money and time when identifying and purchasing 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, Good Pitches, Coarse Pitches and Uncommon Pitches. Make reference to the section on GEAR GAGES for catalog quantities when ordering.
Why Not to Use Worm Gears