Gear Cutting Process, Materials & Tools | What is Gear Cutting | CNCLATHING

2020.7.9

Gear is an important mechanical part for transmitting rotary motion and power from one component to another, widely employed in equipment with speed control mechanism. Among the various types of gear cutting process, which one is the best for manufacturing bevel gear and spur gear? Let’s learn about what is gear cutting, the gear production machines, tools, materials and more.

What is Gear Cutting?

A gear is a rotating machine part with cut teeth or inserted teeth (cogs), which mesh with another toothed part to transmit torque. Gear cutting refers to any machining process of producing gear, including hobbing, broaching, milling, and grinding. Forging, extruding, casting and other forming processes may be executed before the gear cutting process. Many metal and plastic gears are even made without cutting, however, gear cutting is also a substantial industry. 

Types of Gear Cutting Process

Gears can be manufactured by various machining technologies, gear cutting is one of the common gear manufacturing process, which also involves gear generative process, forming process and additive process. Here are the specific cutting operations.

Broaching: a machining process using a toothed tool to remove material for creating the desired gear, work well for cutting teeth on the inside. The most common broaching technique is linear or surface broaching. A vertical broach is often used to manufacture large gears or spline, mounted with a vertical rail with a single tooth cutter to shape the gear accurately and consistently. But the gear cutting machine is relatively expensive and multiple broach sticks are required for different sized gears, usually applied in high production run or odd shapes creation.

Hobbing: using a hob to cut teeth into a blank continuously. On the CNC Gear Hobbing Machines, a master hob or index hob is usually adopted for the gear hobbing process, the cutter and gear blank are rotated at the same time in order to transfer the hob profile onto the material blank. Hobbing is suitable for all sizes of production runs because of its versatility and good productivity, especially for cutting helical and spur gears. 

Milling: applying CNC milling services to cut gears, milling is a subtractive manufacturing method removes materials from blank with a rotating cutter, best for creating coarse-pitch gears and spur gears. The formed milling operations are usually used for manufacturing spur gear. Check our guide for the Difference Between Gear Milling and Gear Hobbing.

Grinding: spur gears can also be ground on a jig grinder utilizing a numbered gear cutter, gear grinding is not really a cutting operation, but it’s a fundamental gear manufacturing process to finish a gear. It’s often used after the heat treatment, for taking out left-over material and achieving an optimal gear quality.

Shaping: an old gear cutting method by mounting a blank in a shaper machine, using a rack cutter or pinion cutter to generate the tooth profile. The first shaping process works well for spur, herringbone, sprocket, internal and cluster gears. And pinion cutting is ideal for low and high production runs. Shaping can also be used for producing bevel gears.

 

After the gear cutting operation, the machined parts can be finished through shaving, burnishing, honing, lapping, and grinding to get a better surface quality. 

Some FAQs About Gear Cutting

1. Which Machines are Used to Cut Gears?

The hobbing machine is one of the most widely used type gear production machines, CNC machines have been developed in the needs of precision and high efficiency, other machines used to cut gears including shaping machines, milling machines, grinder, broach, honing machines and shaving machines. 

2. What Material are Gears Made of?

Generally, the gears are made of metal, plastic, and wood, the gear material should have the high tensile strength to prevent failure against static loads, high endurance strength to withstand dynamic loads, low coefficient of friction and good manufacturability. There are also other options including gray cast iron, nodular and ductile iron, carburizing steel, nitride steel, bronze, reinforced laminates, etc.

3. What Types of Gear Cutting Tools are Used?

A wide range of cutting tools can be selected such as gear hobs, rack milling tools, gear shaper cutters, shaving tools, master gears, ring & plug gauges, broaches, etc. 

4. What are the Common Types of Gears?

There are different types of gears: spur gear, helical gear, double helical gear, herringbone gear, bevel gear, worm gear, etc. Spur gears are the single most common kind of gear, with straight teeth.