Spade bits with angled sides
A spade drill bit has a shaft and a spade head portion arranged on the shaft. The head portion has a rearward facing bottom edge, two longitudinal sides and a forward facing cutting edge. The cutting edge has a pointed, generally triangularly shaped tip and outer ends. The longitudinal sides of the head portion are bent along a bend in a direction of rotation of the drill bit during operation, so that the outer ends are bent forwards in the rotating direction. The bend runs from a first position at one of the longitudinal sides, closer to the bottom edge than to the cutting edge, and to a second position at the cutting edge between the outer end and the tip.
1. A spade drill bit comprising:
a shaft;
a spade head portion arranged on said shaft, said head portion having a rearward facing bottom edge, two longitudinal sides and a forward facing cutting edge having a pointed, generally triangularly shaped tip and outer ends,
wherein said longitudinal sides of said head portion are bent along a bend in a direction of rotation of said drill bit during operation, so that said outer ends are bent forwards in said rotating direction, and wherein said bend runs from a first position at one of said longitudinal sides or said bottom edge, to a second position at said cutting edge between said outer end and said tip,
wherein said cutting edge comprises arced cutting portions arranged between said outer ends and said tip, said arced cutting portions being generally U-shaped.
2. The spade drill bit as recited in claim 1 , wherein edge spurs are arranged at said outer ends of said cutting edge.
3. The spade drill bit as recited in claim 1 further comprising a stem portion for attachment to said shaft and to a hand or power tool.
4. The spade drill bit of claim 3 wherein said stem portion is manufactured by forging, a hot forming technique or a cold forming technique.
5. The spade drill bit as recited in claim 1 , wherein said longitudinal sides comprise serrations.
6. The spade drill bit as recited in claim 2 , wherein said longitudinal sides comprise serrations.
7. The spade drill bit as recited in claim 1 , wherein said tip comprises reliefs arranged in the cutting direction.
8. The spade drill bit as recited in claim 1 , wherein said shaft further comprises means for connecting said shaft to a hand or power tool.
9. The spade drill bit as recited in claim 2 , wherein said tip comprise reliefs arranged in the cutting direction.
10. The spade drill bit as recited in claim 8 wherein said head portion is manufactured by a powder metallurgical process.
11. The spade drill bit as recited in claim 1 , wherein said first position is arranged closer to said bottom edge than to said cutting edge.
12. The spade drill bit as recited in claim 7 , wherein said reliefs are arranged along at least a portion of said bend.
13. The spade drill bit as recited in claim 9 , wherein said reliefs are arranged along at least a portion of said bend.
14. The spade drill bit of claim 4 wherein said shaft and said second stem portion are pressed together and final-sintered.