Why Not to Use Worm Gears
There is one especially glaring reason why one would not select a worm gear over a typical gear: lubrication. The movement between the worm and the wheel equipment 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 usually high viscosity (ISO 320 and greater) and thus are hard to filter, and the lubricants required are usually specialized in what they perform, requiring a product to be on-site specifically for that type of equipment.
Worm Gear Lubrication
The primary 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 reduction in a comparatively small amount of space for what is required if a standard helical gear were used.
This spiral motion also causes an incredibly problematic condition to be the principal mode of power transfer. This is commonly known as 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 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 worm drive shaft 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 accumulates more lubricant, and begins the procedure over again on another revolution.
The rolling friction on a typical gear tooth requires little in the form of lubricant film to complete the spaces and separate both components. Because sliding happens on either aspect of the apparatus tooth apex, a somewhat higher viscosity of lubricant than is definitely strictly necessary for rolling wear must overcome that load. The sliding occurs at a comparatively 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 avoid the worm from touching the wheel is usually to have a film thickness large enough never to have the entire tooth surface wiped off before that section of the worm is out of the load zone.
This scenario requires a special sort of lubricant. Not only will it should be a comparatively high viscosity lubricant (and the bigger the load or temperature, the bigger the viscosity should be), it must have some way to greatly help get over the sliding condition present.
Read The Right Way to Lubricate Worm Gears to find out more on this topic.
Custom Worm Gears
Worm Gears are right angle drives providing huge acceleration ratios on comparatively brief center distances from 1/4” to 11”. When properly mounted and lubricated they function as the quietist and smoothest operating type of gearing. Because of the high ratios possible with worm gearing, optimum speed reduction could be accomplished in less space than 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 level on the helix angle of the worm. Multiple thread worms and gears with higher helix angle prove 25% to 50% more efficient than single thread worms. The mesh or engagement of worms with worm gears generates a sliding action leading to considerable friction and greater loss of efficiency beyond other types of gearing. The use of hardened and surface worm swith bronze worm gears increases efficiency.
LUBRICATION can be an essential factor to boost efficiency in worm gearing. Worm gear action generates considerable high temperature, decreasing efficiency. The quantity of power transmitted at confirmed temperature improves as the performance of the gearing improves. Proper lubrication enhances effectiveness by reducing friction and warmth.
RATIOS of worm equipment sets are determined by dividing the number of teeth in the gear by the amount of threads. Thus one threads yield higher ratios than multiple threads. All Ever-Power. worm gear pieces can be found with either left or right hand threads. Ever-Power. worm gear sets can be found with Single, Dual, Triple and Qua-druple Threads.
Protection PROVISION: Worm gearing should not be used because a locking mechanism to carry large weights where reversing action could cause harm or damage. In applications where potential damage is non-existent and self-locking is preferred against backward rotation then use of a single thread worm with a minimal helix angle instantly 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 steel and hardenedsteel, worms can be found in stainless, aluminium, bronze and nylon; worm gears can be found in steel, hardened steel, stainless, aluminum, nylon and non-metallic (phenolic).
Ever-Power also sells gear tooth measuring products called Ever-Power! Gear Gages decrease mistakes, save time and money when identifying and ordering gears. These pitch templates are available in nine sets to recognize all the regular pitch sizes: Diametral Pitch “DP”, Circular Pitch “CP”, External Involute Splines, Metric Module “MOD”, Stub Tooth, Fine Pitches, Coarse Pitches and Uncommon Pitches. Refer to the section on GEAR GAGES for catalog figures when ordering.
Why Not to Use Worm Gears