Curved-tooth (drum) and straight-tooth couplings are both gear couplings, but the drum gear is the upgrade.
- Capacity: same duty, drum gear is 15~20% higher than straight-tooth.
- Contact: under load nearly all drum-gear teeth engage; straight-tooth only partly → pitting.
- Misalignment: crowned teeth compensate angular (usually ≤1.5°), axial, radial; straight-tooth minimal.
- Life: drum gear long; straight-tooth early pitting.
Verdict: heavy, with misalignment → drum gear; light, minimal offset → straight-tooth works, but drum gear is safer.