• Confirm the worn and damaged condition of the cutting edge.
• In case of extensive chipping on the cutting edge,eliminate with GC wheel.

• Use a collet chuck when installing a drill.The main cutting edge should be parallel from the drill's point view as shown in Fig.1.

• The point angle of the drill should be 140°with the swivel angle designated to 20°as shown in Fig.2.

• Incline the angle of the drill to 10°(Fig3). The angle will be the primary relief angle of the cutting edge.

• After the completion of a single cutting edge, index the drill 180°to grind the another side of the cutting edge. The grinding depth is 0.01-0.02mm per traverse.

<Spark out>
Last, finish the both cutting edges with the grinding depth at 0.01mm. Repeat this procedure 2over3 times including a spark out with a slow traverse for finishing precisely.

<Axial run out>
Maintain the axial run out within 0.01mm .
Grind until the worn and chipped segment of the cutting edge is eliminated.

• After the completion of the primary relief, execute the thinning grinding.
• Incline the drill (work head) to 30°as shown in Fig.4.
• Diamond wheel shaped flat type should be used (Wheel diameter ø100over - ø150).
• The main cutting edge should be vertical from arrow A view as shown in Fig.5.
• Fig.5 also shows the position of the drill point and the grinding wheel.

• Grinding will be done by moving the table to the direction indicated in Fig.4.
• Dimension H, L and W will be required to complete the thinning grinding.
  These three dimensions are indicated in the tool drawing (Fig.6). These values are shown in table 1.
• First, complete the grinding to maintain Dimension H by moving the wheel to horizontal direction (arrow B shown in Fig .5).

• Secondly, maintain Dimension L by moving the wheel to perpendicular direction ( Arrow C shown in Fig.5).
• Last, maintain Dimension W by rotating the drill to Arrow D direction.
  
  
  
• The corner shape of the wheel should be maintained as sharply as possible.
  The management under the following table is recommendable.

• To protect the generating of pressure adhesion, it is effective to grind spark out fully.
  And pay extra attention to the surface finish at the thinning rake face.
  (The surface finish is recommended within 0.4S)

• After the completion of the thinning grinding , grind the secondary relief.Fig.7
  
  
  
• The main cutting edge should be parallel identical as the primary relief grinding process (Fig.7).
• The swivel angle of the drill is designated to 20ßas shown in Fig.8.
• Incline the angle of the drill to 25ß (Fig.9). The angle will be the secondary relief.

• Grind identical way as the primary relief grinding.
• The ridge in the conjunction with the primary relief will appear after the secondary relief grinding.
• Adjust the rotational position of the drill while grinding.
  It is ideal for the ridge to be parallel with the main cutting edge.
• Grind until the both ridges become a straight line.
  It forms a central point on the top of the cutting edge.
• It is easier to adjust a straight line by grinding the secondary relief alternatively.

• If necessary, grind roughly before finish grinding.

• If necessary, grind roughly before finish grinding.
  It is effective to keep sharp edge on the wheel corner.

• If necessary, grind roughly before finish grinding.