MITSUBISHI MATERIALS CORPORATION
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REGRINDING PROCEDURES

SOLID CARBIDE
Check the cutting edge
  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.

Regrinding the front face
  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
fig1,fig2,fig3

Web thinning
  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
fig4

Honing
  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°
fig5

The regrinding work is now complete.
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.
Caution
As a result of regrinding, the coating has been ground off the front flank. Therefore, there will be a reduction in tool life compared with a new product.
Contact your local Mitsubishi Carbide Representative or distributor for authorized regrinding facilities.