Gear Hobbing and Shaping For Precision
Source International – Gear Hobbing / Shaping
Gear Hobbing, Milling and Shaping Is One Of Our Core Capabilities
Gear blanks can be manufactured by most processes (casting, forging, extrusion, powder metallurgy, blanking) but as a rule, machining in the form of hobbing and milling are applied to achieve the final dimensions, shape and surface finish in the gear.
Gear Hobbing is a machining process for gear cutting, cutting splines, and cutting sprockets on a hobbing machine, which is a special type of milling machine. The teeth or splines of the gear are progressively cut into the material (a flat, cylindrical piece of metal) by a series of cuts made by a cutting tool called a hob. Compared to other gear forming processes it is relatively inexpensive but still quite accurate, thus it is used for a broad range of parts and quantities. The hob is basically a worm with gashes cut across it to produce the tooth face cutting edges. All motions in hobbing are rotary, and the hob and gear blank rotate continuously as in two gears meshing until all teeth are cut. Hobbing is one of the most fundamental processes in gear manufacturing. Its productivity and versatility make hobbing the gear manufacturing method of choice for a majority of spur and helical gears.
Gear Hobbing From Source International
The hobbing machines that Source International uses are fully automated and come in many sizes, able to produce anything from tiny instrument gears up to 10 foot (3.0 meter) diameter gears. Each gear hobbing machine typically consists of a chuck and tailstock, to hold the workpiece or a spindle, a spindle on which the hob is mounted, and a drive motor.
Most hobs are single-thread hobs, but double, and triple thread hobs increase production rates. The downside is that they are not as accurate as single-thread hobs. Depending on type of gear teeth to be cut, there are custom made hobs and general purpose hobs.
Types of hobs we use include:
- Roller chain sprocket hobs
- Worm wheel hobs
- Spline hobs
- Chamfer hobs
- Spur and helical gear hobs
- Straight side spline hobs
- Involute spline hobs
- Serration hobs
- Semitopping gear hobs
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Gear shaping is a process for generating gear teeth by a rotating and reciprocating a pinion-shaped cutter. The cutter axis is parallel to the gear axis. The cutter rotates slowly in timed relationship with the gear blank at the same pitch-cycle velocity, with an axial primary reciprocating motion; to produce the gear teeth. A train of gears provides the required relative motion between the cutter shaft and the gear-blank shaft. Cutting may take place either at the down stroke or upstroke of the machine. Because the clearance required for cutter travel is small, gear shaping is suitable for gears that are located close to obstructing surfaces such as flanges. The tool is called gear cutter and resembles in shape the mating gear from the conjugate gear pair, the other gear being the blank.
Gear shaping is one of the most versatile of all gear cutting operations used to produce internal gears, external gears, and integral gear-pinion arrangements. Advantages of gear shaping with pinion-shaped cutter are the high dimensional accuracy achieved and the less expensive tools. The process is applied for finishing operation in all types of production rates.
When the surface finish and dimensional accuracy are not accurate enough for certain applications, several finishing operations are available, including the conventional process of shaving, and a number of abrasive operations, including grinding, honing, and lapping.