Metal cutting drill bit

摘要

A combination drill bit for use in both hand held drills and stationary drill presses has a shanking end, a working end and a helical flute portion between the shanking and working ends. The helical portion has a helix length (L) of;L=(D×πtan⁢⁢α).
The drill bit has a core that is tapered from the working end to the shanking end. A web thickness length at the working end is 10% to 35% of the diameter and the thickness length at the junction of the shanking end is 70% to 90% of the diameter. The drill bit is manufactured from a high speed steel including at least 5% by weight of cobalt.

主权项

1. A drill bit comprising:
a shanking end; a working end; a helical flute portion between said shanking end and said working end, said helical flute portion having a web tapered from said working end to said shanking end such that a web thickness at said working end is from 10% to 35% of the drill bit diameter and a web thickness at a junction of said shanking end is from 70% to 90% of the diameter with a web taper rate of at least 0.080 and a ratio between the web thickness at the working end and the web thickness at the junction of the shanking end is between about 1:2 and 1:5; and said helical flute portion having a helix length ofL=(D×πtan⁢⁢α),L is the helix length, D is the bit diameter, and α is the helix angle, wherein a ratio between the helix length L and the bit diameter D is between about 1:4 to 1:5 and the helix angle α is about 34° and 36°, wherein the drill bit is composed of a high speed steel material having at least 5% cobalt.