Self-drilling screw
Disclosed is a screw for hard wood, comprising a screw tip ( 3 ) with two cutting edges ( 5 ) that extend approximately parallel to each other and perpendicular to the longitudinal axis of the screw. The cutting angle of the cutting edges amounts to about 90°. A centering tip ( 7 ) which slightly protrudes from the two cutting edges ( 5 ) is embodied in the extension of the longitudinal axis of the screw. Said centering tip ( 7 ) prevents the screw from deviating to the side at the beginning of the drilling process.
1. A self-drilling screw having a screw head, a screw shaft, a thread on the screw shaft and a screw tip, the screw tip comprising a pair of cutting edges running essentially normal to the screw's longitudinal axis when viewed along the screw from one side, and a centring tip protruding beyond the cutting edges, wherein the centring tip has a pyramidal shape comprising four faces defining four cutting edges of the centring tip, at least two of said cutting edges of the centring tip running into respective ones of the pair of cutting edges of the screw tip.
2. A screw according to claim 1 , wherein the pair of cutting edges are parallel to one another, as viewed from the screw's tip.
3. A screw according to claim 1 , wherein the two cutting edges are arranged offset from one another, as viewed from the screw's tip.
4. A screw according to claim 1 , wherein both cutting edges lie on a line.
5. A screw according to claim 1 , wherein a contour of a perimeter of a base of the centring tip is shaped as a parallelogram.
6. A screw according to claim 1 , wherein a contour of a perimeter of a base of the centring tip is shaped as a rhombus.
7. A screw according to claim 6 , wherein the cutting edges of the screw tip extend sides of the base of the pyramidal centring tip, as viewed from the screw tip.
8. A screw according to claim 1 , wherein the cutting edges of the screw tip extend cutting edges of the pyramidal centring tip, as viewed from the screw tip.
9. A screw according to claim 1 , wherein the recesses formed following, referred to the direction of the screw's advance, the cutting edges extend over roughly two threads.
10. A screw according to claim 1 , wherein its tip is cold-formed, rather than machined.
11. A screw according to claim 1 , wherein its thread is rolled onto the screw shaft after its tip has been formed.
12. The screw according to claim 1 , wherein the pair of cutting edges of the screw tip run normal to the screw's longitudinal axis.