The machining method is the first decision that shapes the accuracy, lead time and price of a custom gear. Hobbing, shaping and grinding are not interchangeable alternatives: each produces different tooth quality, suits different tooth forms, and carries a different cost. When a buyer understands these differences, the inquiry is faster and the supplier can quote the right process instead of guessing.
Hobbing is the workhorse of gear cutting. A hob cutter rotates in time with the blank and generates the tooth profile continuously, which makes it fast, stable and economical for medium and large batches. Hobbing produces straight and helical spur gears, and the same principle also cuts worms, at a typical accuracy of DIN 7-8. For most industrial applications where a ground finish is not required, hobbing is the default choice.
Shaping is the method of choice when hobbing cannot reach the tooth. A shaping cutter moves vertically while it rolls with the blank, so it can cut internal gears, cluster gears with a shoulder in the way, and other forms that a hob physically cannot enter. Shaping is slower and slightly more expensive per tooth than hobbing, and achieves a similar DIN 7-8 accuracy, which is why it is reserved for internal and shoulder-blocked geometries.
Grinding is the finishing operation that restores accuracy after heat treatment. Hardening distorts teeth by a few microns, so gears that must hold tight tolerances after hardening are hobbed or shaped first and ground afterwards. Grinding achieves DIN 3-6, removes distortion and produces a smooth flank that reduces noise and wear. It is the standard for high-speed, high-torque and noise-sensitive applications, and for any gear that must be paired and matched.
Choosing the right method is a trade-off between geometry, accuracy and quantity. A large batch of external spur gears for agricultural machinery is almost always hobbed. An internal gear or a double gear with a shoulder needs shaping. A precision gear for a servo drive, or a hardened gear that must stay quiet, is hobbed or shaped first and then ground. A competent manufacturer should be able to confirm which combination fits your drawing and volume.
For buyers, the practical checklist is simple: state the required accuracy grade, describe the tooth form (external, internal, helical, worm), and give the expected quantity. With these three facts a supplier can recommend hobbing, shaping, grinding or a combination without delay. At our factory, hobbing, shaping and grinding machines are all in-house, so the recommended process is chosen for your part, not limited by what the shop owns.