Muaj ntau ntau hom iav, thiab cov kev faib feem ntau yog raws li cov yam ntxwv ntawm cov iav ncej. Nws feem ntau muab faib ua peb hom: parallel axis, sib tshuam axis thiab staggered axis.
1.Parallel ncej iav: suav nrog spur iav, helical iav, iav sab hauv, khib thiab helical khib, thiab lwm yam.
2. Intersecting ncej zog: spur bevel iav, kauv bevel iav, xoom hniav bevel iav, thiab lwm yam.
3.Cross ncej zog: muaj cross ncej helical iav, worm gears, hypoid gears, thiab lwm yam.
