Tough Bits

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Fred Bodman
Mr. Shawn Welch
ENG-101-BR6
04 April 2013
Tough Bits
Drilling is the quickest process of removing lots of material. Physical properties of material have a wide range of characteristics and need to have the appropriate drill composition to work properly and efficiently. Many different materials are used for or on drill bits, depending on the required application. Many hard materials, such as carbides, are much more brittle than steel and are far more subject to breaking, especially if the drill is not held at a constant angle to the work piece. The proper drill bit selection can be categorized by the material composition of the workpiece being manufactured which determines its hardness and workability.

High speed steel bits are commonly used to drill typical working metals, hardwood, and most other materials. HSS is a form of tool steel that runs at greater cutting speeds than carbon steel bits, and has largely replaced carbon steels. HSS bits are hard and much more resistant to heat than high carbon steel. These bits hold a sharp edge well and can be sharpened using a standard grinding wheel. HSS bits retain their full strength at high temperatures and will flex to withstand the unique forces of drilling.

When drilling higher temperature alloys such as Titanium, Inconel, and Stainless Steel, a Cobalt composition bit is recommended. Cobalt steel alloys are made of a solid composition of high speed steel which contains more cobalt. Cobalt drill bits are designed for speed and longevity when using proper drilling techniques. They hold their hardness at much higher temperatures and are used to drill hard materials. The main disadvantages of cobalt steels are that they are more brittle than standard HSS, are not easily sharpened when used on abrasive material, and tend to be the more expensive. Carbide bits are typical for drilling abrasive materials like rubber, plastic, bronze, cast iron, cast aluminum, copper, and zinc. These materials tend...
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