BIT MAINTENANCE
Carbide inserts should be ground when the buttons exhibits, flats equal to 1/3rd diameter of the insert.
Original Carbide Dia
Grinding at Dia
13 mm
4 mm
14 mm
5 mm
16 mm
5.6 mm
18 mm
6.0 mm
As the wear of the carbide increases, the rate of penetration goes down. Bit performs best when the carbide inserts (buttons) are in their original shapes. Worn bits have a direct effect on drilling productivity and drilling cost. Grinding can certainly improve drilling results and reduce overall related costs by both extending bit life and providing optimum performance.
Carbide (buttons) are resistant to wear and abrasion, they do indeed develop signs of wear. The most common wear pattern is a "flat" at the impact area. This is most associated with drilling in hard and abrasive rock conditions. As this "flat" area becomes large the effective cutting action is reduced. If not corrected this situation can develop into large problems including carbide "breakage" or "shearing". Grinding at regular intervals assures of maximum bit performance.