Knurled fastener with cutting edges and removable head
A novel fastener comprises a head having a recess for receiving a rotary driver, a shank having knurls defined by generally helical grooves and intersecting generally annular grooves, wherein a plurality of the knurls include a lateral cutting edge, and a generally pointed tip. Another novel fastener comprises a head having a recess for receiving a rotary driver, a shank having a predetermined diameter small enough so that the head will break away from said shank upon application of a predetermined torque, and said shank having knurls defined by generally helical grooves and intersecting generally annular grooves.
1. A fastener for removably fastening a work piece to a steel member comprising:
an elongate shank having an axis, a head for receiving an axial impact for driving said fastener axially forwardly, said head having a recess for receiving a rotary driver, and a generally pointed tip;
said shank having generally helical grooves for imparting clockwise rotation as said fastener is driven axially forwardly, wherein said generally helical grooves intersect generally annular grooves defining knurls, a plurality of said knurls each including a trailing portion angled no more than about 20 degrees from normal for increased pullout strength, a lateral cutting edge for cutting away said steel member when said fastener is rotated in a counterclockwise direction by said rotary driver, and an axially leading portion angled between about 60 degrees and about 70 degrees from normal and tapered toward said generally pointed tip.
2. A fastener according to claim 1 , wherein each lateral cutting edge is on a lateral cutting surface, said cutting surface facing in a counterclockwise direction and being inclined in a clockwise direction.
3. A fastener according to claim 1 , wherein said fastener is heat treated.
4. A fastener for removably fastening a work piece to a steel member comprising:
an elongate shank having an axis, a head for receiving an axial impact for driving said fastener axially forwardly, said head having a recess for receiving a rotary driver, and a generally pointed tip;
said shank having generally helical grooves for imparting clockwise rotation as said fastener is driven axially forwardly, wherein said generally helical grooves intersect generally annular grooves defining knurls, a plurality of said knurls each including a trailing portion for increased pullout strength, a lateral cutting edge for cutting away said steel member when said fastener is rotated in a counterclockwise direction by said rotary driver, and an axially leading portion tapered toward said generally pointed tip;
wherein each lateral cutting edge is on a lateral cutting surface, said cutting surface facing in a counterclockwise direction and being inclined in a clockwise direction; and;
wherein said cutting surface is inclined in said counterclockwise direction from a line normal to said shank by between about 15 degrees and about 25 degrees.
5. A fastener for removably fastening a work piece to a steel substrate comprising:
an elongate shank having an axis, a head for receiving an axial impact for driving said fastener axially forwardly, said head having a recess for receiving a rotary driver, and a generally pointed tip;
said shank having generally helical grooves for imparting clockwise rotation as said fastener is driven axially forwardly, wherein said generally helical grooves intersect generally annular grooves defining knurls, a plurality of said knurls each including a trailing portion angled no more than about 20 degrees from normal for increased pullout strength, a lateral cutting edge, and a leading portion angled between about 60 degrees and about 70 degrees from normal and tapered toward said generally pointed tip; and
wherein said shank has a predetermined diameter that is sized small enough so that said head will break away from said shank upon application of a predetermined torque by said rotary driver if engagement between said knurls and said steel member prevents rotation of said fastener.
6. A fastener for removably fastening a work piece to a steel member comprising:
an elongate shank having an axis, a head for receiving an axial impact for driving said fastener axially forwardly, said head having a recess for receiving a rotary driver, and a generally pointed tip;
said shank having generally helical grooves for imparting clockwise rotation as said fastener is driven axially forwardly, wherein said generally helical grooves intersect generally annular grooves defining knurls, a plurality of said knurls each including a trailing portion for increased pullout strength, a lateral cutting edge for cutting away said steel member when said fastener is rotated in a counterclockwise direction by said rotary driver, and an axially leading portion tapered toward said generally pointed tip;
wherein said helical grooves have a helical angle of between about 5 degrees and about 11 degrees with respect to said axis.