User manual DRILL DOCTOR TWIST DRILL GEOMETRY

[. . . ] Twist Drill Geometry and Cutting Logic (refer to Anatomy of the Drill Bit) History There is evidence the Egyptians used drilling as far back as 4000 B. C. Twist drill bits, as we know them today, are the most common and widely used metal cutting tools. [. . . ] The general rule about POINT ANGLES is that the softer the material the steeper the POINT ANGLE and the harder the material the flatter the POINT ANGLE. Standard drill bits have a 118° point. A drill bit with a 135° point is designed for harder materials. Cutting Logic A twist drill bit penetrates the center of the material it is to remove with its CHISEL POINT. The CHISEL POINT wears into the material to the point where the CUTTING LIPS begin to scoop out the material, making chips. These chips then follow up the FLUTES where they are discharged away from the hole. The hole is then reamed to size by the sharp edge of the LAND which is known as the MARGIN. Drill Point Wear A drill bit begins to wear as soon as it is placed into operation. The maximum drill wear occurs at the corners of the CUTTING LIPS. The CHISEL POINT begins to deform under the heat generated during drilling. The increase in wear at the corners travels back along the LANDS resulting in a reduction in the drill bit diameter and a decrease in tool life. When a drill bit becomes dull it generates more heat and wears faster. In other words, there is a bit of wear on the 10th hole, more still on the 20th hole, and so on. As wear progresses the torque and thrust required also increases. [. . . ] The answer to the flat tire and the dull drill bit is maintenance; air for the tire and sharpening for the drill bit. Sharpening Sharpening a drill bit with a Drill Doctor is the easiest, most efficient way to keep a drill bit from ruining a job, wasting time, and ending up in the coffee can with the other dull drill bits. www. drilldr. com · 800/597-6170 HS Professional Tool Manufacturing, LLC · 210 East Hersey Street. ­ PO Box 730 ­ Ashland, OR 97520 DD Geometry 04-00 Rev. 01 [. . . ]