Flexible drill shaft

Abstract

A method of making a flexible drill shaft. The method comprising: winding wire to form a helical coil spring, applying a mechanical deformation to the wire as it is being wound and using the helical coil spring to form a flexible drill shaft. The mechanical deformation applied results in the wire after being wound having a cross section such that when an axial load is applied to the drill shaft there is planar contact between adjacent coils of the spring.

1 . A method of making a flexible drill shaft, the method comprising:
 winding wire to form a helical coil spring;   applying a mechanical deformation to the wire as it is being wound; and   using the helical coil spring to form a flexible drill shaft;   wherein the mechanical deformation applied results in the wire after being wound having a cross section such that when an axial load is applied to the drill shaft there is planar contact between adjacent coils of the spring.   
   
   
       2 . A method of making a flexible drill shaft according to claim  9  comprising:
 applying a preload as the wire is being wound.   
   
   
       3 . A method according to claim  9  or  10  comprising using dimensional or thermal expansion to tightly assemble two or more coil springs.