Worm gears are often used when large velocity reductions are needed. The decrease ratio is determined by the number of starts of the worm and amount of the teeth on the worm gear. But worm gears possess sliding get in touch with which is quiet but tends to produce heat and also have relatively low transmitting efficiency.
For the materials for production, in general, worm is constructed of hard metal while the worm gear is made from relatively soft steel such as for example aluminum bronze. That is since the number of tooth on the worm gear is relatively high in comparison to worm using its number of begins being usually 1 to 4, by reducing the worm gear hardness, the friction on the worm tooth is reduced. Another feature of worm manufacturing is the need of specialized machine for gear cutting and tooth grinding of worms. The worm gear, however, may be made with the hobbing machine used for spur gears. But because of the different tooth shape, it isn’t possible to cut many gears at once by stacking the gear blanks as can be carried out with spur gears.
The applications for worm gears include gear boxes, fishing pole reels, guitar string tuning pegs, and in which a delicate rate adjustment by utilizing a sizable speed reduction is needed. While you can rotate the worm gear by worm, it is usually extremely hard to rotate worm utilizing the worm gear. That is called the personal locking feature. The self locking feature cannot continually be assured and another method is recommended for true positive reverse prevention.
Also there exists duplex worm gear type. When using these, you’ll be able to adapt backlash, as when one’s teeth put on necessitates backlash adjustment, without requiring a change in the center distance. There are not too many manufacturers who can create this type of worm.
The worm equipment is more commonly called worm wheel in China.
A worm equipment is a gear comprising a shaft with a spiral thread that engages with and drives a toothed wheel. Worm gears are an old style of gear, and a edition of one of the six basic machines. Basically, a worm equipment is certainly a screw butted up against what appears like a standard spur gear with slightly angled and curved tooth.
It changes the rotational motion by 90 degrees, and the plane of movement also changes due to the placement of the worm on the worm wheel (or just “the wheel”). They are typically comprised of a steel worm and a brass wheel.
Worm Gear
Figure 1. Worm gear. Most worms (but not all) are at underneath.
How Worm Gears Work
An electric motor or engine applies rotational power via to the worm. The worm rotates against the wheel, and the screw face pushes on one’s teeth of the wheel. The wheel can be pushed against the load.
Worm Gear Uses
There are a few reasons why you might select a worm gear more than a standard gear.
The first one is the high reduction ratio. A worm gear can have a massive reduction ratio with little effort – all one must do is add circumference to the wheel. Thus you can use it to either significantly increase torque or greatly reduce speed. It will typically take multiple reductions of a conventional gearset to achieve the same reduction level of a solitary worm gear – meaning users of worm gears have got fewer shifting parts and fewer locations for failure.
A second reason to use a worm gear may be the inability to reverse the direction of power. Because of the friction between the worm and the wheel, it really is virtually difficult for a wheel with pressure applied to it to start the worm moving.
On a standard equipment, the input and output could be switched independently once enough force is used. This necessitates adding a backstop to a typical gearbox, further increasing the complication of the apparatus set.
Why Not to Use Worm Gears
There is one especially glaring reason why one would not choose a worm gear over a standard gear: lubrication. The movement between your worm and the wheel equipment faces is completely sliding. There is absolutely no rolling element of the tooth contact or interaction. This makes them relatively difficult to lubricate.
The lubricants required are often high viscosity (ISO 320 and better) and thus are difficult to filter, and the lubricants required are usually 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 simultaneously. The spiral movement allows large sums of decrease in a comparatively little bit 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 put on.
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With an average gear set the power is transferred at the peak load stage on the tooth (known as the apex or pitchline), at least in a rolling wear condition. Sliding occurs on either aspect 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 over the tooth of the wheel, it slowly rubs off the lubricant film, until there is absolutely no lubricant film still left, and for that reason, the worm rubs at the metallic of the wheel in a boundary lubrication regime. When the worm surface leaves the wheel surface, it accumulates more lubricant, and starts the process over again on another revolution.
The rolling friction on a typical gear tooth requires small in the way of lubricant film to fill in the spaces and separate both components. Because sliding happens on either part of the gear tooth apex, a somewhat higher viscosity of lubricant than can be strictly needed for rolling wear must overcome that load. The sliding occurs at a relatively low velocity.
The worm on a worm set gear turns, and while turning, it crushes against the load that is imposed on the wheel. The only method to prevent the worm from touching the wheel is to have a film thickness large enough to not have the whole tooth surface wiped off before that area of the worm is out of the load zone.
This scenario requires a special kind of lubricant. Not just will it should be a comparatively high viscosity lubricant (and the bigger the strain or temperature, the bigger the viscosity should be), it will need to have some way to help conquer the sliding condition present.
Read The Right Way to Lubricate Worm Gears for more information on this topic.
Viscosity may be the major aspect in stopping the worm from touching the wheel in a worm gear set. As the load and size of gearing determines the required lubricant, an ISO 460 or ISO 680 is fairly common, and an ISO 1000 isn’t unheard of. If you have ever tried to filter this selection of viscosity, you understand it is problematic because it is likely that non-e of the filters or pumps you have got on-site would be the appropriate size or ranking to function properly.
Therefore, you would likely need to get a particular pump and filter for this kind of unit. A lubricant that viscous takes a slower operating pump to avoid the lubricant from activating the filter bypass. It will also require a huge surface area filter to permit the lubricant to stream through.
Lubricant Types to Look For
One lubricant type commonly used with worm gears is mineral-based, compounded equipment oils. There are no additives which can be put into a lubricant that can make it overcome sliding wear indefinitely, but the organic or synthetic fatty additive combination in compounded gear oils results in good lubricity, providing an extra way of measuring protection from metal-to-metal get in touch with.
Another lubricant type commonly used in combination with worm gears is mineral-based, industrial extreme pressure (EP) equipment oils. There are some problems with this type of lubricant in case you are using a worm gear with a yellow steel (brass) component. However, if you have relatively low operating temperatures or no yellow metal present on the apparatus tooth areas, this lubricant is effective.
Polyalphaolefin (PAO) equipment lubricants work very well in worm equipment applications because they naturally have good lubricity properties. With a PAO gear oil, it is necessary to view the additive bundle, because these can possess EP additives. A standard-duty antiwear (AW) fortified gear oil will typically be acceptable, but check that the properties are compatible with most metals.
The author recommends to closely watch the put on metals in oil analysis testing to ensure that the AW package isn’t so reactive concerning trigger significant leaching from the brass. The effect should be far less than what will be seen with EP actually in a worst-case scenario for AW reactivity, nonetheless it can arrive in metals tests. If you want a lubricant that can handle higher- or lower-than-typical temps, a suitable PAO-based product is probable available.
Polyalkylene glycols (PAG), a fourth type of lubricant, are becoming more prevalent. These lubricants have superb lubricity properties, , nor contain the waxes that cause low-temperature problems with many mineral lubricants, making them a great low-temperature choice. Caution must be taken when using PAG oils because they’re not appropriate for mineral oils, and some seals and paints.
Metallurgy of Worm Gears
The most common worm gears are created with a brass wheel and a steel worm. That is since the brass wheel is typically easier to replace than the worm itself. The wheel is made out of brass because it is designed to be sacrificial.
In the event that the two surfaces come into contact, the worm is marginally safe from wear since the wheel is softer, and therefore, most of the wear occurs on the wheel. Oil analysis reports on this type of unit almost always show some level of copper and low degrees of iron – as a result of the sacrificial wheel.
This brass wheel throws another problem in to the lubrication equation for worm gears. If a sulfur-phosphorous EP gear essential oil is put into the sump of a worm gear with a brass wheel, and the temperature is definitely high enough, the EP additive will activate. In normal steel gears, this activation generates a thin coating of oxidation on the surface that helps to protect the gear tooth from shock loads and other extreme mechanical conditions.
On the brass surface area however, the activation of the EP additive outcomes in significant corrosion from the sulfur. In a brief timeframe, you can eliminate a significant portion of the strain surface of the wheel and trigger major damage.
Other Materials
Some of the less common materials found in worm gear sets include:
Steel worm and steel worm wheel – This software doesn’t have the EP problems of brass gearing, but there is absolutely no room for mistake included in a gearbox like this. Repairs on worm gear sets with this combination of metal are usually more costly and additional time eating than with a brass/steel worm gear set. This is because the material transfer connected with failure makes both worm and the wheel unusable in the rebuild.
Brass worm and brass worm wheel – This program is most likely within moderate to light load situations because the brass can only hold up to a lesser quantity of load. Lubricant selection upon this metal mixture is flexible due to the lighter load, but one must still consider the additive restrictions regarding EP because of the yellow metal.
Plastic on metal, on plastic, and other comparable combinations – This is typically found in relatively light load applications, such as robotics and auto components. The lubricant selection depends upon the plastic in use, because many plastic types react to the hydrocarbons in regular lubricant, and thus will demand silicon-based or other non-reactive lubricants.
Although a worm gear will always have a couple of complications compared to a typical gear set, it can simply be a highly effective and reliable device. With a little focus on set up and lubricant selection, worm gears can provide reliable service as well as any other kind of gear set.
A worm drive is one simple worm gear set mechanism when a worm meshes with a worm gear. Even it is basic, there are two important elements: worm and worm equipment. (Also, they are known as the worm and worm wheel) The worm and worm wheel is important motion control element providing large swiftness reductions. It can reduce the rotational acceleration or increase the torque output. The worm drive motion advantage is that they can transfer motion in right angle. In addition, it has an interesting property: the worm or worm shaft can easily turn the gear, but the gear can not convert the worm. This worm drive self-locking feature let the worm gear includes a brake function in conveyor systems or lifting systems.
An Introduction to Worm Gearbox
The most important applications of worm gears is used in worm gear box. A worm gearbox is called a worm decrease gearbox, worm equipment reducer or a worm drive gearbox. It contains worm gears, shafts, bearings, and box frames.
The worm equipment, shafts, bearings load are supported by the container shell. Therefore, the gearbox housing will need to have sufficient hardness. Or else, it will result in lower tranny quality. As the worm gearbox has a durable, transmitting ratio, little size, self-locking capacity, and simple framework, it is often used across a wide variety of industries: Rotary table or turntable, material dosing systems, car feed machinery, stacking machine, belt conveyors, farm choosing lorries and more automation industry.
How to Select High Efficient Worm Gearbox?
The worm gear production process is also relatively simple. However, there is a low transmission effectiveness problem if you don’t understand the how to select the worm gearbox. 3 basic indicate choose high worm gear efficiency that you need to know:
1) Helix position. The worm equipment drive efficiency mostly rely on the helix position of the worm. Generally, multiple thread worms and gears is more efficient than one thread worms. Proper thread worms can increase performance.
2) Lubrication. To select a brand lubricating oil is an essential factor to boost worm gearbox performance. As the proper lubrication can reduce worm gear action friction and warmth.
3) Materials selection and Gear Manufacturing Technology. For worm shaft, the material should be hardened steel. The worm gear material ought to be aluminium bronze. By reducing the worm equipment hardness, the friction on the worm teeth is reduced. In worm production, to use the specialized machine for gear trimming and tooth grinding of worms can also increase worm gearbox effectiveness.
From a sizable transmission gearbox power to an even small worm gearbox load, you can choose one from a wide range of worm reducer that precisely fits your application requirements.
Worm Gear Container Assembly：
1) You may complete the set up in six various ways.
2) The installation should be solid and reliable.
3) Ensure that you check the connection between the motor and the worm gear reducer.
4) You must make use of flexible cables and wiring for a manual set up.
By using the most advanced science and drive technology, we have developed several unique “square box” designed from high-quality aluminium die casting with a beautiful appearance. The modular worm gearbox design series: worm drive gearbox, parallel shaft gearbox, bevel helical gearbox, spiral bevel gearbox, coaxial gearbox, right angle gearbox. An NMRV series gearbox is usually a standard worm gearbox with a bronze worm equipment and a worm. Our Helical gearbox product line consists of four universal series (R/S/K/F) and a step-less swiftness variation UDL series. Their structure and function are similar to an NMRV worm gearbox.
Worm gears are made of a worm and a gear (sometimes known as a worm wheel), with non-parallel, nonintersecting shafts oriented 90 degrees to one another. The worm is definitely analogous to a screw with a V-type thread, and the apparatus is usually analogous to a spur gear. The worm is typically the driving component, with the worm’s thread advancing one’s teeth of the gear.
Like a ball screw, the worm in a worm gear may have an individual start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each complete turn (360 degrees) of the worm advances the gear by one tooth. So a gear with 24 teeth provides a gear reduction of 24:1. For a multi-begin worm, the apparatus reduction equals the amount of teeth on the gear, divided by the number of begins on the worm. (That is not the same as most other types of gears, where the gear reduction is usually a function of the diameters of the two components.)
The worm in a worm gear assembly can have one start (thread) or multiple starts.
Image credit: Kohara Gear Industry Company, Ltd.
The meshing of the worm and the gear is a mixture of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding actions causes friction and heat, which limits the efficiency of worm gears to 30 to 50 percent. In order to minimize friction (and therefore, warmth), the worm and gear are made from dissimilar metals – for example, the worm could be produced of hardened steel and the gear manufactured from bronze or aluminum.
Although the sliding contact reduces efficiency, it provides very quiet operation. (The utilization of dissimilar metals for the worm and equipment also contributes to quiet operation.) This makes worm gears suitable for use where noise should be minimized, such as for example in elevators. Furthermore, the use of a softer materials for the gear implies that it can absorb shock loads, like those skilled in heavy equipment or crushing devices.
The primary benefit of worm gears is their ability to provide high reduction ratios and correspondingly high torque multiplication. They can also be used as rate reducers in low- to moderate-acceleration applications. And, because their decrease ratio is founded on the amount of gear teeth alone, they are more compact than other types of gears. Like fine-pitch business lead screws, worm gears are usually self-locking, making them perfect for hoisting and lifting applications.
A worm gear reducer is one kind of reduction gear container which includes a worm pinion insight, an output worm gear, and features a right angle output orientation. This kind of reduction gear package is normally used to have a rated motor acceleration and produce a low speed output with higher torque value based on the decrease ratio. They often can solve space-saving problems because the worm equipment reducer is among the sleekest reduction gearboxes available because of the small diameter of its output gear.
worm gear reducerWorm equipment reducers are also a favorite type of rate reducer because they provide the greatest speed decrease in the smallest package. With a higher ratio of speed decrease and high torque result multiplier, it’s unsurprising that lots of power transmission systems make use of a worm gear reducer. Some of the most typical applications for worm gears can be found in tuning instruments, medical screening equipment, elevators, protection gates, and conveyor belts.
Torque Transmission offers two sizes of worm equipment reducer, the SW-1 and the SW-5 and both are available in a range of ratios. The SW-1 ratios include 3.5:1 to 60:1 and the SW-5 ratios include 5:1 to 100:1. Both these options are produced with durable compression-molded glass-fill polyester housings for a long lasting, long lasting, light-weight speed reducer that is also compact, noncorrosive, and nonmetallic.
Features
Our worm gear reducers offer an option of a solid or hollow output shaft and feature an adjustable mounting placement. Both the SW-1 and the SW-5, however, can withstand shock loading better than other reduction gearbox styles, making them ideal for demanding applications.
Rugged compression-molded glass-fill up polyester housing
Light weight and compact
Non corrosive
Non metallic
Range of ratios
SW-1, 3.5:1 to 60:1
SW-5, 5:1 to 100:1
Grease Lubrication
Solid or Hollow output shaft
Adjustable mounting position
Overview
Technical Info
Low friction coefficient on the gearing for high efficiency.
Powered by long-long lasting worm gears.
Minimum speed fluctuation with low noise and low vibration.
Lightweight and compact in accordance with its high load capacity.
Compact design
Compact design is among the key phrases of the typical gearboxes of the BJ-Series. Further optimisation may be accomplished through the use of adapted gearboxes or unique gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is due to the very smooth operating of the worm gear combined with the use of cast iron and high precision on element manufacturing and assembly. Regarding the our precision gearboxes, we consider extra care of any sound which can be interpreted as a murmur from the gear. So the general noise degree of our gearbox can be reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This frequently proves to be a decisive advantage making the incorporation of the gearbox substantially simpler and smaller sized.The worm gearbox can be an angle gear. This is often an edge for incorporation into constructions.
Strong bearings in solid housing
The output shaft of the BJ worm gearbox is very firmly embedded in the apparatus house and is perfect for immediate suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, BJ-Gear’s worm gearboxes provides a self-locking impact, which in many situations can be used as brake or as extra protection. Also spindle gearboxes with a trapezoidal spindle are self-locking, making them well suited for a wide variety of solutions.

Additional information regarding Helical Gear Reducer can be found below.