Gears
 

GEAR MANUFACTURING

Gear Manufacturing -- From Broaching to Milling

Gear ManufacturingGear materials are usually made up of a composition of carbon and low alloy steel, including carburized steels. The application for which the gear is intended determines the choice of the material. To site an example, all gears made for food processing applications are made of stainless steel, or nickel-base alloys. The material is chosen for its corrosion resistant property. There are multiple ways that gear processing could be done, where gear blanks are put through different cutting and finishing process. These processes are:

Broach
Broach is a type of metalwork, where the broach consists of a set of chisel points mounted on a single piece of steel, which progressively become taller. This tool is used for enlarging a circular hole into a shape that is not circular, such as, as square or any other shape. This tool is also used for cutting thin strip on the metal or a square keyway. This is done when manufacturing gears, driveshaft, pulleys, etc. The amount of material removed by the broach chisel depends on the material that is being cut. As an example, if the material happens to be steel, the broach tooth might remove 0.0025 inch, while the one designed to cut brass would remove as much as 0.004 inch.

Grinding
The grinding machine is typically used for finishing purposes or for making very light cuts, which is done by a rotating abrasive wheel. Typically these wheels come in various shapes and sizes, and made up of carious kinds of stones. In making the grinding wheel, stones of diamonds or organic materials are used. The wheel rotates at a speed that depends on the size of the grinder, and is power driven. The material is held in a bed-fixture, which guides and holds the work-piece. Either the grind wheel is made to move towards the work-piece or the work-piece moves towards the grinder.

Honing
The improvement of geometry in manufacturing of precision bores, the surface finish, and the dimensional properties of the work-piece are all done by the hone machine tool. The process so accomplished by the machine, is called honing. During the finishing process, the grind stone is held against the work-piece applying a force which differs from material to material.

Hobbing
This is a machine tool that is used for cutting gears. It is a milling machine that is used to form the gear blank as both rotate simultaneously at a fixed gearing ratio. The profile of the cutter is in the form of a helix, and this helps to generate curve on the sides of the teeth of the gear under process.

Lapping
It is a machine process, in which two surfaces are finished by rubbing with each other, with an abrasive in between the two. This is either done by hand or by a machine.

Milling Machine
To bring a complex shape on to metals and other solid materials, a milling machine is used. A rotating cutter or an endmill rotates on an axis held by a spindle, somewhat like a drilling machine, and a moving table, where the work-piece is held affixed by a jig, is moved towards the stationary rotating tool to accomplish the desired cutting action. In modern machines, this is done by the computer numerical control (CNC) machines.