Spur gears transmit rotary motion between parallel shafts and don't generate axial thrust: a pushing force that causes the gears to separate and misalign. Also known as straight-cut gears, they have disc-shaped bodies and straight teeth that project outward from their axis and mesh with parts that lie in the same plane. Different-sized spur gears change speed and multiply torque. Spur gears paired with gear racks convert rotary motion into linear motion. Typical uses for spur gears include appliances, machinery, and pumps.