Radius gimlet point anti-stripout screw

Abstract

A self-tapping screw includes a head, a shaft, a tapered end and a rounded distal tip. A thread includes a thread start on the tapered end. The axial position of the thread start and a first full thread, the radius of the round distal tip and the diameter of the tapered end at the thread start are controlled in relation to the screw size for consistent, improved screw performance.

What is claimed is:  
     
         1 . A thread-forming tapping screw for screw sizes each having a standard diameter tolerance, said screw to be inserted in a pilot hole having a pilot hole diameter for each screw size, said screw comprising: 
 a head;    a shaft extending from said head, said shaft defining a minor diameter of said screw, and including a tapered end having a distal tip; and    a helical thread on said shaft, said thread including a thread start disposed at a position on said tapered end an axial distance from said distal tip related by a common thread start factor to a mean minor diameter determined from an average of said pilot hole diameter and said pilot hole diameter minus said tolerance for all said screw sizes.    
     
     
         2 . The screw of  claim 1 , said thread start factor being between about 0.4 and about 0.5 for all said screw sizes.  
     
     
         3 . The screw of  claim 1 , said thread start factor being about 0.451 for all said screw sizes.  
     
     
         4 . The screw of  claim 1 , said tapered end having a diameter at said thread start related to said mean minor diameter by a common diameter factor for all said screw sizes.  
     
     
         5 . The screw of  claim 1 , said distal tip have a rounded shape formed on a radius related to said mean minor diameter by a common radius factor for all said screw sizes.  
     
     
         6 . The screw of  claim 1 , said thread having a first full thread on said shaft an axial distance from said distal tip related to said mean minor diameter by a common distance factor for all said screw sizes.  
     
     
         7 . The screw of  claim 1 , said thread provided at about 18 threads per inch length of said shaft for all said screw sizes.  
     
     
         8 . The screw of  claim 1 , said threads having a thread angle of about fifty-eight degrees for all said screw sizes.  
     
     
         9 . A thread-forming tapping screw for screw sizes each having a standard diameter tolerance, said screw to be inserted in a pilot hole having a pilot hole diameter for each screw size, said screw comprising: 
 a head;    a shaft extending from said head, said shaft defining a minor diameter of said screw, and including a tapered end having a distal tip; and    a helical thread on said shaft, said thread including a thread start disposed on said tapered end, said tapered end having a diameter at said thread start related by a common diameter factor to a mean minor diameter determined from an average of said pilot hole diameter and said pilot hole diameter minus said tolerance for all said screw sizes.    
     
     
         10 . The screw of  claim 9 , said diameter factor being between about 0.6 and about 0.7 for all said screw sizes.  
     
     
         11 . The screw of  claim 9 , said diameter factor being about 0.68 for all said screw sizes.  
     
     
         12 . The screw of  claim 9 , said distal tip have a rounded shape formed on a radius related to said mean minor diameter by a common radius factor for all said screw sizes.  
     
     
         13 . The screw of  claim 9 , said thread having a first full thread on said shaft an axial distance from said distal tip related to said mean minor diameter by a common distance factor for all said screw sizes.  
     
     
         14 . The screw of  claim 9 , said thread provided at about 18 threads per inch length of said shaft for all said screw sizes.  
     
     
         15 . The screw of  claim 9 , said threads having a thread angle of about fifty-eight degrees for all said screw sizes.  
     
     
         16 . A thread-forming tapping screw for screw sizes each having a standard diameter tolerance, said screw to be inserted in a pilot hole having a pilot hole diameter for each screw size, said screw comprising: 
 a head;    a shaft extending from said head, said shaft defining a minor diameter of said screw, and including a tapered end having a distal tip; and    a helical thread on said shaft, said thread including a thread start disposed on said tapered end, said distal tip have a rounded shape formed on a radius related by a common radius factor to a mean minor diameter determined from an average of said pilot hole diameter and said pilot hole diameter minus said tolerance for all said screw sizes.    
     
     
         17 . The screw of  claim 16 , said radius factor being between about 0.2 and about 0.3 for all said screw sizes.  
     
     
         18 . The screw of  claim 16 , said radius factor being about 0.287 for all said screw sizes.  
     
     
         19 . The screw of  claim 16 , said thread having a first full thread on said shaft an axial distance from said distal tip related to said mean minor diameter by a common distance factor for all said screw sizes.  
     
     
         20 . The screw of  claim 16 , said thread provided at about 18 threads per inch length of said shaft for all said screw sizes.  
     
     
         21 . The screw of  claim 16 , said threads having a thread angle of about fifty-eight degrees for all said screw sizes.  
     
     
         22 . A thread-forming tapping screw for screw sizes each having a standard diameter tolerance, said screw to be inserted in a pilot hole having a pilot hole diameter for each screw size, said screw comprising: 
 a head;    a shaft extending from said head, said shaft defining a minor diameter of said screw, and including a tapered end having a distal tip; and    a helical thread on said shaft, said thread including a thread start disposed on said tapered end, said thread having a first full thread on said shaft an axial distance from said distal tip related by a common distance factor to a mean minor diameter determined from an average of said pilot hole diameter and said pilot hole diameter minus said tolerance for all said screw sizes.    
     
     
         23 . The screw of  claim 22 , said distance factor being between about 1.04 and about 1.05 for all said screw sizes.  
     
     
         24 . The screw of  claim 22 , said distance factor being about 1.048 for all said screw sizes.  
     
     
         25 . The screw of  claim 22 , said thread provided at about 18 threads per inch length of said shaft for all said screw sizes.  
     
     
         26 . The screw of  claim 22 , said threads having a thread angle of about fifty-eight degrees for all said screw sizes.  
     
     
         27 . A thread-forming tapping screw for screw sizes each having a standard diameter tolerance, said screw to be inserted in a pilot hole having a pilot hole diameter for each screw size, said screw comprising: 
 a head;    a shaft extending from said head, said shaft defining a minor diameter of said screw, and including a tapered end having a distal tip;    a helical thread on said shaft;    said thread including a thread start disposed at a position on said tapered end an axial distance from said distal tip related by a common thread start factor to a mean minor diameter determined from an average of said pilot hole diameter and said pilot hole diameter minus said tolerance for all said screw sizes;    said thread having a first full thread on said shaft an axial distance from said distal tip related to said mean minor diameter by a common distance factor for all said screw sizes;    said tapered end having a diameter at said thread start related to said mean minor diameter by a common diameter factor for all said screw sizes; and    said distal tip have a rounded shape formed on a radius related to said mean minor diameter by a common radius factor for all said screw sizes.    
     
     
         28 . The screw of  claim 27 , said thread provided at about 18 threads per inch length of said shaft for all said screw sizes.  
     
     
         29 . The screw of  claim 27 , said threads having a thread angle of about fifty-eight degrees for all said screw sizes.