1. Check the worn and/or damaged condition of the cutting edge.
2. If the cutting edge is chipped, remove the damaged part using a green wheel.

1. The face can be ground by a three rake system. With the use of a twist drill grinder or a universal tool and cutter grinder, set the drill to 20° for a 140° point angle as shown in Figure 1.
2. Grind the flank so that the first angle of 10°~12° is obtained as shown in Figure 2. Index and grind the other cutting edge. Spark out and maintain lip heights within .0008".
3. Next, tilt the drill an additional 10° and grind the flank so that a second angle of 20°~22° as shown in Figure 3. Grind the second angle so the edge line between the first and second angle aligns with the center of the drill.
   A conical grind is also acceptable.
   • Grinding wheel; Diamond cup type
     230 grit to 400 grit Φ4 inch to Φ6 inch

1. Thin along the edge of the chisel at 90° as shown in Figure 4, leave .002"~.004" behind center.
2. Next, turn the drill 10°~15° to create a pocket of 100°~105°. This forms the third facet angle.
   • Grinding wheel; Diamond flat type 230 grit to 400 grit

1. Hone the chisel edge per chart below
   • Diamond files: T-1-140 for roughing, T-0-400 for finishing, T-0-1500 for ultra-fine finishing
2. Hone uniformly over the entire cutting edge.
   • Diamond files: T-1-140 for roughing, T-0-400 for finishing, T-0-1500 for ultra-fine finishing
3. Hone width
   

   Drill Diameter	Hone Width
   .188" less	.002×30"
   .188" over .391" less	.002~.004×30°
   .391" over	.004~.006×30°

Check the following before using the drill:

• Check if the lip height difference is within .0008".
• Check if there was a failure to regrind a damaged part of the cutting edge.
• Check if the honing is properly done.
• Check if there are any grinding burrs.