A gear hobbing cutting machine, also known as a hobbing machine or spur cutter, is an industrial type of edge-cutting tool used in metalworking to cut gears. A gear hobber cuts teeth into the edges of a round metal disc called a “workpiece.”
The workpiece sits on a rotatable table called an “idler” or “driven” table and is pushed into a rotating cutter head on the end of a rotating shaft called a spindle. The hobbing machine cuts both external and internal gears. Internally, the cutter head rotates in one direction (external in the opposite direction as the workpiece is pushed by hand or automatically). In some machines, the speed at which the cutterhead rotates can be varied. Internally cut gears are usually made on internal hobbing machines.
Gear hobbers usually use either a reciprocating cutter head or a rotary table to expose one tooth at a time to the cutter. Rotary tables are typically used for external cutters, although some universal machines can cut external and internal gears.
The most precise cutting tools used in industrial gear manufacturing are hobbing machines. Which were invented by Ernst Wenzl in 1873 in Vienna, Austria-Hungary (now Austria). Wenzl’s hobbing machine was an industrial version of the hand-held monochrome engraver.
Starting in the early 1900s, a gear hobbing machine can typically be found in any shop that makes gears and bearings. Hobbing machines are also used by many internal gear manufacturing shops because they are fairly inexpensive to operate and require little maintenance. A hobbing machine, however, is not well suited for external gears that require multiple cuts of teeth.
Gear hobbing machines are most commonly used in small manufacturing shops. They are slower in production rates when compared to more modern gear manufacturing machines. Some of the first hobbing machines were water powered, and powered by steam engines. In the late 1950s, antifriction bearings were perfected for use with hobbing machines and production rates increased dramatically due to their reliability and low cost. Currently , you can find almost everywhere.
How is it used?
The term “gear hob” is often used as a generic term to describe any internal or external gear cutting machine. The smallest type of gear cutting machine is called a “milling cutter.” They are intended for use with smaller-sized gears.
Hobbing machines are used to cut gears from bar stock. The workpieces must be heat treated to an appropriate hardness level prior to cutting. The workpieces can be straight or tapered (taperlock hobbing machines are available). Straight workpieces are usually used for internal gears, while tapered workpieces are most commonly used for external gears. Tapered gear hobbing machines usually have a dial indicator on the driven table that indicates when the gears have been pushed together far enough (zero backlash).
The drivetrain is usually rotated in one direction, and the cutter is rotated in the opposite direction. For example, a spindle can rotate clockwise as it pushes a gear into a counter-clockwise cutterhead.
A gear hob cutter has a fixed cutterhead and a movable idler table. The idler table is usually adjustable along three axes. Allowing for adjustments to be made to the cutting position of the cutter. A spurting cutter can be used to machine many different types of gears, but it is most commonly used for machine tools with external cutters (in part because external cutters allow for larger gear hob diameters). Spurting tooling is also called ” in some publications. The spurting cutterhead typically has two-sided (two-flute) teeth.