Visually, the flexible spiral reminds a spring with a big step of the screw line, however, from a spring it is distinguished by a profile of cross section. The flexible spiral is usually made of a steel wire by method of plastic deformation, with the subsequent heat treatment and greasing. Such technology does not allow formation of keen edges or agnails on spiral surfaces. The ready spiral is taken up in bays 100 m that significantly reduces its transport dimensions. Thus make spirals with a diameter from 32 mm to 100 mm. Flexible spirals are used as working body of the screws having the nonlinear route and giving rather easy products with a small productivity. It is connected with the fact that flexible spirals have no central axis for transfer of considerable efforts and transportation carries out only due to own rigidity of a spiral.
