Gear cutting is the manufacturing process used to form teeth on gears, splines, sprockets, and related power-transmission parts. The process must control tooth profile, pitch, concentricity, surface finish, and material condition because small errors can lead to noise, vibration, heat, and premature wear.
Depending on geometry and quantity, gears may be made with dedicated gear equipment or with flexible CNC machining methods. The best route depends on gear type, accuracy class, batch size, material, and whether heat treatment or finishing is required.
Common Gear Cutting Methods
| Method | How It Works | Best Fit |
|---|---|---|
| Hobbing | A rotating hob progressively generates teeth | Spur and helical gears in production |
| Shaping | A reciprocating cutter forms teeth | Internal gears and shoulders near obstructions |
| Gear milling | A form cutter or CNC tool machines each tooth space | Prototypes, low volume, large gears |
| Broaching | A broach cuts internal profiles in one pass | Internal splines and high-volume features |
| Grinding | Abrasive wheel finishes hardened gear teeth | High accuracy and improved surface finish |
Important Gear Design Factors
- Module or diametral pitch defines tooth size.
- Pressure angle affects strength and mesh behavior.
- Face width influences load capacity and stiffness.
- Material and heat treatment determine wear resistance.
- Runout and concentricity affect smooth rotation.
CNC Milling for Gear Prototypes
For prototypes and low-volume gears, CNC milling can be practical because it avoids special tooling and allows fast geometry changes. It is not always the fastest method for high-volume production, but it works well when the design is still evolving or the gear is part of a larger machined assembly. MTSPi can review whether milling-based production is suitable for your geometry.
Material Choices
Steel alloys are common for high-load gears because they can be hardened. Brass and bronze are used when low friction or corrosion resistance is needed. Aluminum may fit lightweight, low-load applications. Engineering plastics can reduce noise and weight, but require careful attention to temperature and wear.
Inspection for Gear Quality
Gear inspection may include tooth thickness, pitch error, runout, profile, surface finish, and hardness. For assemblies that must run quietly, measurement should go beyond simple outside diameter checks. Connect the inspection plan with the quality requirements before production.
Related MTSPi Resources
FAQ
What is the difference between gear hobbing and gear milling?
Hobbing generates teeth continuously with a hob, while milling often cuts tooth spaces one at a time or with programmed toolpaths.
Can CNC machines make gears?
Yes, especially prototypes, custom gears, and low-volume parts. Dedicated gear equipment may be better for large quantities.
Do gears need heat treatment?
Many metal gears do, especially when load and wear resistance are important.
