a small spool for threats, wire etc in a machine

spool

one of a series of teeth on the rim of a wheel which transfers motion by locking into the teeth of a smaller wheel

main part of device

a small table on wheels, used for serving food

circle, revolution

a circular object that turns (as on carts, cars, bicycles etc and machines); to push or pull (something) (a vehicle with wheels); to turn in a curve or circle

circle, revolution