Helical Gears

Parallel Shaft Application	Right Angle Shaft Application	Manufacturing
Selection Process	Types	Application
Cooling and Lubrication

Helical gears are a type of industrial gears. These gears have angled teeth that creates a thrust load on the gears while they are meshing. They are circular in shape. Their teeth is curved along a helical path. There is a refinement in design, which helical gears enjoy over Spur gears. Actually the leading edges of the teeth in Helical Gears are designed in such a way as not to be parallel to the axis of rotation. Instead, they are set angularly. As the gear shape is curved, the unique angle makes the tooth shape to be like a segment of helix. The angled Helical Gear teeth is able to engage more gradually than the spur gear teeth and makes it run in more smoothly and quietly as well.

Power and motion transmitted by Helical-toothed gears can be between right-angle axes (same-hand) and parallel shafts (opposite hand). There is also scope for using non-parallel shafts.

Parallel Shaft Application
While using these gears through Parallel shaft application, there is marked improvement that translates into a smoother action as compared to spur gears. This happens because with successive teeth coming into action, there is uniform and gradual transfer of load. There is also the added advantage of reduced level of noise and vibration. In the parallel shaft engagement, these gears need a pair of hand gears that is opposite of each other. Like one right-hand with one left-hand helical gear.

Parallel shaft Application

Right Angle Shaft Application
For transmitting power and motion between shafts at a right angle (90 degree), helical gears of the same hand are put to use. Actually hand selection is dictated by the direction of thrust. It usually is based upon the location of thrust bearings.

Application Gear

Types of Helical Gears
There are different types of helical gears such as follows:

Manufacturing of Helical Gears
Materials from which helical gears can be manufactured includes all the grades of steel, stainless, iron, brass, plastic, phenolic, rawhide, bronze etc. Actually there are many factors that can contribute to selecting the right material. They are design, power transmission obligations, noise, heat generation and absence or presence of corrosive elements. For the process of manufacture forging casting and then Hobbing are effectively used.

Identification of Right or Left hand Gears
To identify whether the Helix Gear you intend to use is Left Hand or Right hand, please perform this little experiment. Place the helical gears on a table. You will see, that the teeth is appearing to be leaning either to the right (///) or to the left (\\\). So gear in question is either left-hand or right-hand solely based on the direction of leaning threads.


Right Hand Gears	Left Hand Gears

Selection Process of Helical Gears
Important parameters that needs to be given a thought in specifying Helical Gears are the following:

Number of teeth
Face or width of the tooth
Pitch Diameter
Outside diameter
Gear hand direction
Pressure angle
Manufacturing material
Mounting methods
- Hub
- Shaft

Application of Helical Gears
Find application in a variety of industries. They include:

Steel industry
Mining industry
Packaging machinery
Rubber industry
Textile industry
Specialty machinery
OEM equipment Manufacturers
Conveyors
Pumps and pumping equipment
Medical industry
Defence industry
Material handling conveyors
Automotive industry
Blower, Feeder
Mixers and agitators

Helical Gear Boxes: Helical gear boxes are very popular in applications that involves high shock loads. Although Helical gear boxes require a considerable initial investment, but they can maintain high efficiency. This is the plus point of Helical Gear Boxes.

Helical Gear Motors: Helical Gear motors are designed to work in agitating applications that are subjected to high overhung, axial loads and flexural torque.

Cooling and lubrication of High speed Helical Gears
It is use in checking the speed of centrifugal compressors and turbines. That is the reason why so much importance is placed on the exact lubrication and cooling of helical Gears. These are vital for a successful operation. As the gears mesh, there is rolling of tooth surfaces and also sliding against each other. This is shown in the images.

Actually improper cooling results in Gear surface distress. This can take the forms of:

Scuffing
Scuffing is damage of the tooth surface. The signs are characterized by radial scratch lines. Scuffing takes place when the lubricant's oil film thickness is typically less than the collective roughness of the pinion and gear, and there is metal-to-metal touch.
Wear
Ideally there should be a low rate of wear. This can happen with the supply oil is perfectly filtered and that abrasive wear does not take place due to suspension of hard particles in the oil.
Micropitting
Micropitting can also take place if there is improper or insufficient lubrication. It can lead to Gear tooth damage, noise and vibration.
Micropatting
In case of high-speed gears, if the oil film is not thick enough to check metal-to-metal contact then the problem of Micropatting could occur.
Thermal problems
In high-speed helical gears, the teeth could get easily distorted because of uneven temperature distribution through the face width of the gearing. This can be prevented by proper lubrication of the Gear surfaces.