Drill for machining fiber reinforced composite material

Abstract

A diamond coated drill capable of drilling holes in fiber reinforced composite materials. The drill is made from a tungsten carbide (WC) substrate with cemented cobalt (Co) in a range between about 3 to 10 wt. % and a diamond coating having a thickness in a range between 3 to 20 microns. The drill includes a shank, a longitudinal axis and includes two flutes at a helix angle that is in a range between 25 and 35 degrees with respect to the axis. A margin width is maintained between about 5 to 10 percent of the drill diameter. A body clearance diameter is maintained at between about 92 to 96 percent of the drill diameter. A web thickness before splitting is about 20 to 30 percent of the drill diameter. A clearance angle or lip relief angle is between about 10 and 20 degrees. A chisel edge angle is between about 105 and 120 degrees. A chisel edge length is up to about 0.035 mm. A splitting angle is between about 130 and 150 degrees. A notch angle is between about 30 and 40 degrees with respect to the drill axis. A notch rake angle lies between about -5 and 10 degrees. A split point angle is between about 70 and 100 degrees, and preferably about 90 degrees.

Description

Background technique

[0001] Carbon fiber reinforced polymers (CFRP) include a wide range of composite materials with different fiber types, fiber orientations, fiber contents, and matrix materials. The use of fiber reinforcements has been growing steadily in many industries in recent years. For example, CFRP composites have found increasing applications in the aerospace and automotive industries due to their high specific strength and high specific stiffness. As the use of such materials increases, there will be an increasing need for a cost-effective method that can produce high quality holes in such materials that are sized within narrow tolerances.

[0002] However, CFRP composites pose huge problems in terms of processing. Currently, the market is dominated by polycrystalline diamond (PCD) drill bits. Typical defects after drilling with conventional PCD bits include spalling, fiber pull-out, burning and the like, such as Figure 8 shown.

[0003] It has been recognized...

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