In most industrial applications, the two main types of gears are helical gears and worm gears. Many people would traditionally opt for helical gearbox models to worm gearboxes, but advances in the latter have given them an edge over the former. In this post, we take a closer look at worm gears to determine where and how they are used.

What is a Worm Gear?

A worm gear is a type of gear designed with a shaft featuring a spiral thread that engages and drives a toothed wheel. It is used to change the direction of rotational movement of a shaft by 90 degrees. Worm gears are also used for reducing speed in compact spaces. In most cases, the worm is made of steel, while the wheel is designed using brass. See the demonstration below:

The main Types of Worm Gears 

Worm gears can be classified into two main categories, cylindrical models and double enveloping type:

1. Cylindrical Worm Gears 

Cylindrical worm gears have an involute rack from where the spur gears are created. Their rack teeth feature straight walls, but when used to create teeth on the gear blanks, they form familiar teeth of the involute spur gear. Then, the rack tooth winds around the worm’s body. 

The worm wheel is made of helical gear teeth cut at an angle to match that of the worm teeth. The meshing is like a rack moving a pinion, but the translation motion is changed by the worm’s rotary motion. In most cylindrical worm gears, the wheels have at least 24 teeth, and the wheel more than 40. In some cases, the worms can be cut directly on the shaft fitted to the motor or on a separate piece, which is fitted on the shaft.

2. Enveloping Worm Gears 

In these types of gears, enveloping is used to indicate the way worm wheel teeth partially wrap around the worm. This helps to provide a large contact area. To achieve this, designers shape the worm surface to match the curvature of the worm wheel. However, this setup is complex and requires extra care, especially with axial positioning.

Applications Using Worm Gears

Because of their compressed nature and non-reversible operations, worm gears are very common in many devices, especially large equipment. Here are some of them: 

• Lifts  

In addition to helping reduce the speed of application and change direction of motion, they are also considered secondary braking systems because pressure cannot be applied backward. This is why they are preferred for most lifts, material handling and hoist systems.

• Conveyor Belt Drive System

As we have highlighted, worm gears only move in one direction, making them a perfect pick for industrial conveyor belts. At home, they are preferred for moving security gates. 

• Gearboxes  

As we have demonstrated, worm gears help change the direction and alter the speed of rotational movement. Therefore, they work very well in gearboxes. Indeed, you are likely to find worm gears in equipment such as mining, presses, rolling mills, and small machinery.

Conclusion 

Worm gears are very useful because of their special attributes, especially for changing the direction of motion and the fact that motion happens only in one direction. Remember to ensure you only acquire high-quality worm gears and follow a good lubrication program for optimal performance.