All About Burrs
CTI – Carbide Tools for Industry, Inc.
November 2008Go Back to www.burrs4less.com
Carbide Tools for Industry, Inc. (CTI) circa 1955 features a wide variety of the finest quality Carbide Burrs made of premium micro grain carbide and carefully ground on state of the art 5-axis computer numerical control (CNC) tool grinders. Carbide burrs and rotary files are used in various applications for deburring, cylinder head porting, mold making, tool and die, metalworking, tool grinding, foundry, aerospace, automotive, dental laboratory, wood carving, farriers, metal smithing, sculpting, welding, chamfering, jewelry manufacturing, die casting, and metal casting. The purpose of the research is to define burrs (rotary file), describe the chemical composition, the history of tool making, the uses/applications and what the future holds for carbide burrs.
Burrs which are also known as rotary files which consist of small and large shaped cutters used in die grinders, rotary tools, and dentist’s drills. The name may be considered suitable when their mini-size head (3 mm diameter shaft) is closely similar to that of a seed in the burr fruit. Carbide burrs are also used in CNC machining robot “type” centers for removing burrs (the small flakes of metal) after a machining process (Burrs-cutting, n.d.) To sustain the right external speed and cutting environment they are rotated at the maximum velocity achievable, appropriate with their size and structure.
In engineering, a burr can be described as the raised circumference on metal. It may be present in the form of a fine wire on the edge of a freshly sharpened tool or as a raised portion on a surface, after being struck a blow from an equally hard or heavy object. Specifically, burrs are as a rule useless residual that is the effect after machine grinding, drilling, milling, or turning. In the following report the word, burr, refers to the excess substance of material and carbide burr refers to the tool that removes the excess material.
The process of removing burrs, the small flakes of metal, is known as deburring. Burr creation in machining accounts for a major part of the costs for manufacturers throughout the world. Drilling burrs, for example, are common when drilling almost any material. The Boeing 747 airplane has approximately 1.3 million holes drilled in it most of which have to be deburred to some extent (Burrs-metal, April 2007). As one could imagine, the cost and time needed to perform these drilling and deburring operations is significant.
In addition to drilling, milling is also a source of burr formation in machining. A good example of unwanted burrs is in the automotive industry where cylinder blocks, pistons and other engine components are cast then milled to a specific dimension. With higher demands placed on accuracy and precision, burr formation is of critical importance because it can affect engine performance, reliability, and durability (Burrs-metal, April 2007).
& Cobalt Compounds
In 1758, the Swedish chemist and mineralogist, Axel Fredrik Cronstedt, discovered and described an unusually heavy mineral that he called "tung-sten", which is Swedish for heavy stone. (Tungsten history, n.d.) During the 19th century, cobalt blue was produced at the Norwegian Blaafarvevaerket (70-80% of world production), led by the Prussian industrialist Benjamin Wegner. In 1938, John Livingood and Glenn Seaborg discovered cobalt-60 (Cobalt, n.d.).
Modern machine tools date from about 1775, when the English inventor John Wilkinson (1728–1808) constructed a horizontal boring machine for producing internal cylindrical surfaces. About 1794 Henry Maudslay (1771–1831) developed the first engine lathe. Later, Joseph Whitworth (1803–87) speeded the wider use of Wilkinson's and Maudslay's machine tools by developing, in 1830, measuring instruments accurate to a millionth of an inch. His work was of great value because precise methods of measurement were necessary for the subsequent mass production of articles having interchangeable parts (Machine Tools, n.d.).
The earliest attempts to manufacture interchangeable parts occurred almost at the same time in Europe and the U.S. These efforts relied on the use of so-called filing jigs, which parts could be hand-filed to identical dimensions. The first true mass-production system was created by the American inventor Eli Whitney, who in 1798 obtained a contract with the U.S. government to produce 10,000 army muskets, all with interchangeable parts.
During the 19th century, such standard machine tools as lathes, shapers, planers,
grinders, and saws and milling,
drilling, and boring machines reached a fairly high degree of precision, and
their use became widespread in the industrializing nations. During the early
part of the 20th century, machine tools
were enlarged and made even more accurate. After 1920 they became more
specialized in their applications. From about 1930 to 1950 more powerful and
rigid machine tools were built to utilize effectively the greatly improved
cutting materials that had become available. These specialized machine tools
made it possible to manufacture standardized products very economically, using
relatively unskilled labor. The machines lacked flexibility, however, and they
were not adaptable to a variety of products or to variations in manufacturing
standards. As a result, in the past three decades engineers have developed
highly versatile and accurate machine
tools that have been adapted to computer control, making possible the
economical manufacture of products that are complex in design.
(Machine Tools, n.d.)
CHEMICAL COMPOSITION OF A BURR
Burr cutters are made from tungsten carbide which allows them to move at high speeds and yet still sustain their cutting edges. Carbide cutting surfaces are often useful when machining through materials such as carbon and stainless steel as well as in situations where other tools would wear away, such as high-quantity production runs. Usually, carbide will leave a better finish on the tool, and permit quicker machining. Carbide tools can also endure higher temperatures than standard high speed tools. The material is usually tungsten-carbide cobalt, also called "cemented carbide", a metal matrix composite where tungsten carbide particles are the aggregate and metallic cobalt serves as the matrix (Tungsten Carbide, n.d.)
The process of combining tungsten carbide with cobalt is referred to as sintering or Hot Isostatic Pressing (HIP). During this process cobalt eventually will be entering the liquid stage and WC grains (>> higher melting point) remain in the solid stage. Machining with carbide can be difficult, as carbide is more brittle than other tool materials, making it susceptible to chipping and breaking. To offset this, many manufacturers sell carbide inserts and matching insert holders. With this setup, the small carbide insert is held in place by a larger tool made of a less brittle material (usually steel). This gives the benefit of using carbide without the high cost of making the entire tool out of carbide. Most modern face mills use carbide inserts, as well as some lathe tools and end mills (Tungsten Carbide, n.d.).
USES & APPLICATIONS
Carbide burrs are used for rapid removal of excess materials. Ironically, burrs are both referred to as the excess shavings of material and the actual carbide burr “tool” used to remove rough edges after the machining process. The removal of burrs from jagged, sharp edges is another common application for carbide burrs. In addition, carbide burrs are a supplemental type of tool that is used prior to polishing or finishing with coated abrasives. Carbide burrs can be used on cast iron, steel and aluminum. Depending on the type of surfaces that are accessible, carbide burrs can be utilized because of the different shapes in which they are manufactured. Typically, carbide burrs are made in ˝ inch diameter shapes such as round, cylindrical and oval. Carbide burrs are created with different cuts. Single or double cuts are used for steel and cast iron surfaces. According to Monroe (1997, p. 28), a course single cut minimizes the tendency of the cutter to load up with aluminum.
A die grinder is a handheld tool which turns a burr at a high rate of speed. It is usually pneumatic (powered by compressed air), although electric die grinders are also common. The burr is held in a bit holding device and may be changed as required. The rotational speed of a pneumatic die grinder is adjusted by a hand-operated throttle which allows the operator to fluctuate the volume of compressed air entering the tool. Die grinders are used to drudge away small amounts of metal from piece of work. The name comes from their use in touching up hardened steel dies (Die grinder, n.d.).
Most die grinder throttles feature a spring-loaded "kickstand" mechanism between the throttle lever and the body of the grinder, which prevents the throttle from opening (being pressed down towards the body of the grinder) without operator intervention. This prevents the die grinder from accidentally activating (Die grinder, n.d.).
Porting is another method in which application of the carbide burr is necessary. Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve the quality and quantity of the gas flow. Porting the heads provides the finely detailed attention required to bring the engine to the highest level of efficiency. Theoretically, polishing with abrasives affects the fuel flow and ultimately the porting process is responsible for the high power output of modern engines (Cylinder Head Porting June 2008).
Lastly, another common application and use of the carbide burr is utilized by sculptures. They provide vibration-free cutting and grinding. The shank is made of high tensile stainless steel. Diamond burrs are created by bonding diamond particles by means of electroplating with uniform size and exceptionally sharp-edged for fast cutting. Carbide burrs are precision fluted and can cut just about any material such as bronze, brass, aluminum, steels, wood, and all types of stone.
FUTURE OF CUTTING TOOLS
In the late 1990s, a total of 2,096 establishments operated in the industry. In 2000, hand and edge tool manufacturers shipped $7.6 billion worth of goods in 2000, while cutting tool and machine tool accessory manufacturers shipped $5.6 billion worth of goods (Cutting tools, machine etal, n.d.).
According to the United States Census Bureau (2002), cutting tools, machine tool accessories, and precision measuring devices industry is facing transition. Increased global competition in all aspects of manufacturing has created demand for better, longer lasting tools and accessories. Extensive development of tougher cutting tool materials and coatings has been the driving force of change in this industry, along with improved cutting tool design that lends extended performance. Increased emphasis on quality control is affecting the measuring device segment through demand for electronic gauges that link to statistical process control software packages. Modular tooling designs have affected the accessories segment.
Ironically, while this industry has paced itself to match industry demand for productivity improvements, it is also has met with its own problems. The influx of foreign competitors to this market has been staggering, forcing cutting tool and measuring device manufacturers to look introspectively at their own operations. Process improvements and increased development became commonplace practices to remain profitable.
A downturn in the machine tool industry does not necessarily correlate to the health of the cutting tool industry. Generally, cutting tool sales are viewed as an economic indicator of the nation's manufacturing productivity level. The difference primarily is capital expense. A corporation may decide to purchase a used machine tool over a new one in recessionary times. However, if a company is cutting metal, the cutting tools wear or break and must be sharpened or replaced with new cutting tools. Therefore, the productivity of a metal cutting company generally is directly related to the purchasing levels of machine tools. However, longer lasting cutting tools are being manufactured with specialized coatings that extend the wear life of the tool—sometimes as much as four times the normal wear. With improved cutting tool materials and geometry, the volume of machine tool sales will inevitably drop because the tools are designed to reduce the frequency of replacement (Cutting tools, machine etal, n.d.).
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