Tungsten Carbide Brad Point Drill Bit Ⅱ

In last part we know that while boring wood, tungsten carbide brad point drill bits can position precisely with its pointed tips, remove chips fast with their wide flutes, and produce accurate and clean-edged holes with the double spurs.This part we will explain further the mechanism of brad point drill bits.

Conventional twist drill bits tend to wander when presented to a flat workpiece. For metalwork, this is countered by drilling a pilot hole with a spotting drill bit. In wood, the tungsten carbide brad point drill bit is another solution: The center of the drill bit is given not the straight chisel of the twist drill bit, but a brad with a sharp point and four sharp corners to cut the wood. The sharp point of the spur simply pushes into the soft wood to keep the drill bit in line.

Metals are typically isotropic, and an ordinary twist drill bit shears the edges of the hole cleanly. Wood drilled across the grain has long strands of wood fiber. These long strands tend to pull out of the wood hole, rather than being cleanly cut at the hole edge. The tungsten carbide brad point drill bit has the outside corner of the cutting edges leading, so that it cuts the periphery of the hole before the inner parts of the cutting edges plane off the base of the hole. By cutting the periphery first, the cutting spurs maximizes the chance that the fibers can be cut cleanly, rather than having them pull messily out of the timber.

(To be continued. This article is divided into 5 parts, and this is part 2. For part 1, please refer to http://news.chinatungsten.com/en/tungsten-information/80396-ti-10360; for part 3, please refer to http://news.chinatungsten.com/en/tungsten-information/80398-ti-10362)

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