Method of manufacturing a bi-metal screw

Abstract

The present invention pertains to a method of manufacturing a bi-metal screw comprising a sequence of procedures; wherein, the process preparation is for arranging a shank portion and a drilling portion made of different materials; the shank portion has a planar welding surface defined thereon; in particular, the drilling portion includes a conical section with a conical surface defined on the top face thereof. While operating, the conical section is gradually welded to the planar welding surface to form a composite screw, so as to smooth the air away for preventing the interspaces generated within the junction of the two portions and rendering the composite screw not to be slanted aside. Subsequently, an integral bi-metal screw is formed through the processes of precisely cutting and formation, thereby increasing the quality of the screw.

1 . A method of manufacturing a bi-metal screw comprising the steps of:
 a procedure of preparation for arranging a shank portion and a drilling portion, which are respectively made of different materials; wherein, said shank portion consists of a screw head disposed on one end thereof and a planar welding surface formed on the other end thereof; a central axis is longitudinally defined from a center of said drilling portion, which has a conical section disposed thereon; said conical section has an outer diameter greater than a shank diameter of said drilling portion; wherein, said conical section includes a conical surface defined at the top face thereof and a bottom surface defined opposite to said conical surface; said bottom surface intersects to an outmost tip of said conical surface, thereby inwardly extending toward the direction of said drilling portion and engaging thereto;   a procedure of welding for welding said planar welding surface of said shank portion to said conical section of said drilling portion; a composite screw is formed by welding;   a procedure of cutting to chip and remove a scrap generated out of the junction of said planar welding surface and said conical section;   a procedure of formation for molding a drill tip at the distal end of said drilling portion and continuously rolling a plurality of screw threads on said composite screw, hence a bi-metal screw is accomplished.   
   
   
       2 . A method of manufacturing a bi-metal screw comprising the steps of:
 a procedure of preparation for arranging a shank portion and a drilling portion, which are respectively made of different materials; wherein, said shank portion consists of a screw head disposed on one end thereof and a planar welding surface formed on the other end thereof; a central axis is longitudinally defined from a center of said drilling portion, which includes a conical section disposed on one end thereof and a drill tip formed on the other end thereof; a scrap stock is disposed around the outer circumference of said drill tip; said conical section has an outer diameter greater than a shank diameter of said drilling portion; wherein, said conical section includes a conical surface defined at the top face thereof and a bottom surface defined opposite to said conical surface; said bottom surface intersects to an outmost tip of said conical surface, thereby inwardly extending toward the direction of said drilling portion and engaging thereto;   a procedure of welding for welding said planar welding surface of said shank portion to said conical section of said drilling portion; a composite screw is formed by welding;   a procedure of cutting to chip and remove a scrap generated out of the junction of said planar welding surface and said conical section;   a procedure of formation for continuously rolling a plurality of screw threads on said composite screw and removing said scrap stock disposed around said drill tip, hence said bi-metal screw is accomplished.   
   
   
       3 . A method of manufacturing a bi-metal screw as claimed in  claim 1  or  2 , wherein said bottom surface is inclined to said central axis and has a sharp angle with said conical surface. 
   
   
       4 . A method of manufacturing a bi-metal screw as claimed in  claim 1  or  2 , wherein said conical surface is formed in a rough state.