NOTICE
You can ruin a drill bit by grinding it too long or too forcefully. Frequently dip the bit in water to cool it and retain its original hardness. If the tip becomes blue or purple, it may have overheated and be too soft to use.
3.While pressing the collet holder forward gently, rotate the drill bit back and forth, and about every four seconds, dip the bit in water to cool the tip. This will help prevent the tip from overheating and softening too much.
4.Continue grinding until the machine stops making grinding sounds.
5.Remove the collet holder and drill bit, rotate them 180º, then reinsert the collet holder and drill bit into the front grinding area.
6.Repeat Steps 3 & 4.
7.Examine the point angle.
Note: It is not necessary to grind a back relief on a standard bit. However, doing so will ensure the bit cuts more efficiently.
Figure 20. No unground surfaces remain on bit
after point angle grinding (top view).
—If the surface of the drill bit retains unground material, try grinding the bit again, or use a different point angle setting.
—If the point angle is not shaped evenly, repeat Steps 1-6, using even pressure to grind both sides of the bit.
H8203 Professional Drill Sharpening Machine
Rear Trimming Area
The grinding wheel grinds a back relief on stan- dard and split point bits in the rear trimming area. Adding back relief to a standard bit makes it more efficient in removing material from a workpiece. Some trial and error will be needed to determine the correct amount of back relief, as shown in Figures 21 & 22.
Back Relief
Figure 21. Correct back relief for standard bit.
Back Relief
Figure 22. Correct back relief for split point bit.
To add back relief to a standard bit:
1.Loosen the cap screws (Figure 23) on the rear trimming area and lower the set screw to raise the adjusting block to its highest posi- tion.
Adjusting
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