Peripheral wear determines tool life
Carbide drills require higher accuracy than high-speed steel drills. Therefore, when regrinding, NC grinding machines are generally used instead of conventional grinding machines. In general, the drill’s flank faces and web thinning are reground, and to complete the process the cutting edge is honed. For solid drills, regrinding can be usual undertaken approximately 20 times, while for brazed drills, the length of the carbide insert restricts the number of regrinds.
After several regrinds the flute length shortens and the diameter decreases slightly due to the back taper.
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1. Primary relief grinding
Repeat step 1 and 2 on the opposite side.
2. Secondary relief grinding
Repeat step 1 and 2 on the opposite side.
3. Web thinning, face grinding
Repeat step 1 and 2 on the opposite side.
4. Cutting edge honing
Repeat on the other cutting edge.
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