Why Not to Use Worm Gears
There is one particularly glaring reason why one would not select a worm gear over a standard gear: lubrication. The movement between the worm and the wheel gear faces is entirely sliding. There is no rolling element of the tooth contact or interaction. This makes them fairly difficult to lubricate.
The lubricants required are often very high viscosity (ISO 320 and higher) and therefore are difficult to filter, and the lubricants required are usually specialized in what they do, 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 worm drive shaft transfers power. It is a boon and a curse at the same time. The spiral motion allows huge amounts of decrease in a comparatively small amount of space for what’s required if a typical helical equipment were used.
This spiral motion also causes a remarkably problematic condition to be the principal mode of power transfer. This is often called sliding friction or sliding use.
With an average gear set the power is transferred at the peak load stage 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 fairly low.
With a worm gear, sliding motion may be 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 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 picks up more lubricant, and begins 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 both components. Because sliding occurs on either aspect of the apparatus tooth apex, a slightly higher viscosity of lubricant than is usually 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, even though turning, it crushes against the load that’s imposed on the wheel. The only way to avoid the worm from touching the wheel is definitely to get a film thickness huge enough to not have the entire tooth surface wiped off before that part of the worm is out of the strain zone.
This scenario requires a special kind of lubricant. Not only will it should be a comparatively high viscosity lubricant (and the higher the strain or temperature, the bigger the viscosity should be), it will need to have some way to greatly help overcome the sliding condition present.
Read The Right Method to Lubricate Worm Gears to learn more on this topic.
Custom Worm Gears
Worm Gears are correct angle drives providing huge rate ratios on comparatively short center distances from 1/4” to 11”. When correctly 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 could be accomplished in much less space than a great many other types of gearing. Worm and worm gears are powered by nonintersecting shafts at 90° angles.
EFFICIENCY of worm gear drives depends to a big degree on the helix angle of the worm. Multiple thread worms and gears with higher helix angle prove 25% to 50% more efficient than one thread worms. The mesh or engagement of worms with worm gears creates a sliding action leading to considerable friction and higher loss of efficiency beyond other types of gearing. The use of hardened and surface worm swith bronze worm gears boosts efficiency.
LUBRICATION can be an essential factor to improve effectiveness in worm gearing. Worm equipment action generates considerable high temperature, decreasing efficiency. The quantity of power transmitted at confirmed temperature improves as the efficiency of the gearing raises. Proper lubrication enhances performance by reducing friction and high temperature.
RATIOS of worm gear sets are dependant on dividing the number of teeth in the apparatus by the number of threads. Thus solitary threads yield higher ratios than multiple threads. All Ever-Power. worm gear sets 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 should not be used as a locking mechanism to hold heavy weights where reversing actions 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 a single thread worm with a low helix angle immediately locks the worm equipment drive against backward rotation.
MATERIAL recommended for worms is definitely hardened steel and bronze for worm gears. However, depending on the application form unhardened metal 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, aluminium, bronze and nylon; worm gears can be found in steel, hardened metal, stainless, aluminum, nylon and nonmetallic (phenolic).
Ever-Power also sells equipment tooth measuring gadgets 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 recognize all the standard pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, External Involute Splines, Metric Module “MOD”, Stub Tooth, Great Pitches, Coarse Pitches and Uncommon Pitches. Refer to the section on Equipment GAGES for catalog amounts when ordering.