Method of making a tool for extracting a broken screw
View Patent ↗The method of making a tool for removal of broken screws from a base material, including the material of the bone of a medical patient. One end of the tool has an open bore with interior, left-hand tapered screw threads formed thereon by compressing the tool to form the taper after the threads are formed and presented in a cylindrical shape. The other end of the tool is solid for accommodating a driving tool which rotates the tool in the removal of the broken screw.
1. A method of making a tool for the removal of broken screws from a base material, comprising the steps of:
providing a tool body body with a longitudinal axis and an external frusto-conical terminal end with the larger diameter of said end being at an axial location spaced axially inwardly along said body and with said body having an interior cylindrical wall concentric with said axis and extending for a length into said body and presenting a cylindrically shaped bore,
forming screw threads on said wall and having said threads extend along said wall to the axial extent to said location, and
after the threading step, compressing said body in the area of said location to change the shape of said wall, and thereby said threads, from said cylindrical shape to an inwardly tapered shape.
2. The method of making a tool for the removal of broken screws from a base material, as claimed in claim 1 , further comprising:
said body is compressed by swaging said body in the area of said location to form said tapered shape.
3. A method of making an instrument for the removal of broken screws from bone, comprising the steps of:
providing an instrument body with a longitudinal axis and an external frusto-conical terminal end with the larger diameter of said end being at an axial location spaced axially inwardly along said body and with said body having an interior cylindrical wall concentric and said axis and extending for a length into said body and presenting a cylindrically shaped bore,
forming screw threads on said wall and having said threads extend along said wall to the axial extent to said location, and
after the threading step, compressing said body in the area of said location to change the shape of said wall, and thereby said threads, from said cylindrical shape to an inwardly tapered shape.
4. The method of making an instrument for the removal of broken screws from bone, as claimed in claim 3 , wherein:
said body is compressed by swaging said body in the area of said location to form said tapered shape.
5. The method of making an instrument for the removal of broken screws from bone, as claimed in claim 4 , wherein:
said screw threads are formed as left-hand threads, and heat treating said body.
6. The method of making an instrument for the removal of broken screws from bone, as claimed in claim 5 , including:
forming grooves in said wall and extending axially on said body and through said screw threads to have said screw threads discontinuous in their circular extent.