Cutting by use of rotating axially moving tool – Tool having crystalline cutting edge
Patent
1993-04-28
1996-12-03
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Tool having crystalline cutting edge
40753119/, 408230, B23B 5102
Patent
active
055801960
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to wear-resistant tools for cutting and drilling and in particular to wear-resistant rotary cutting tools for machining metals and other materials.
2. Description of the Related Art
Almost every product made by the engineering industries requires at some stage in its manufacture the machining of metals or other materials. Typical machining operations include drilling, milling, reaming, thread cutting, slot cutting, and turning. Typically, these operations are carried out by automated machine tools which are fitted replaceably and often interchangeably with tool bits such as drill bits, end mills, thread taps, slot drills and reamers. The preferred shapes of the various cutting tools are well known in the art and will not be described further here.
The material from which the cutting tools are made must combine as far as possible the properties of resistance to deformation (hardness), resistance to fracture (toughness), and resistance to wear (durability). The most widely used materials for this purpose are steel and tungsten carbide. However, both steel and tungsten carbide are prone to wear in the operating environment and as a result cutting tools made of these materials need to be removed for sharpening or replacement quite frequently. The expense of sharpening or replacing the steel or tungsten carbide tool bits, and the machine tool downtime that is needed for their frequent replacement, add considerably to the total cost of the manufacturing process and interfere with the smooth operation of production lines.
Abrasive compacts are also well known in the art and are used extensively in industry for the abrading of various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70 percent, preferably 80 to 90 percent, by volume of the compact bonded into a hard conglomerate. Compacts are polycrystalline masses and can replace single large crystals in many applications. The abrasive particles of compacts are invariably ultra-hard abrasives such as diamond and cubic boron nitride. Compacts containing diamond abrasive particles are known in the art by the initials PCD. Compacts containing cubic boron nitride abrasive particles are known as PCBN.
Abrasive compacts generally contain a second phase or bonding matrix which contains a catalyst (also known as a solvent) useful in synthesising the particles. In the case of cubic boron nitride, examples of suitable catalysts are aluminium or an alloy of aluminium with nickel, cobalt, iron, manganese or chromium. In the case of diamond, examples or suitable catalysts are metals of Groups VIII of the Periodic Table such as cobalt, nickel or iron or an alloy containing such a metal.
As is known in the art, diamond and cubic boron nitride compacts are manufactured under conditions of temperature and pressure at which the abrasive particle is crystallographically stable.
Abrasive compacts may be bonded directly to a tool or shank for use. Alternatively, they may be bonded to a backing such as a cemented carbide backing prior to being mounted on a tool or shank. Such backed compacts are also known in the art as composite abrasive compacts.
The backing will typically be made of cemented carbide such as cemented tungsten carbide, cemented tantalum carbide, cemented titanium carbide or a mixture thereof.
Hitherto, machining tools comprising PCD or PCBN cutting edges have generally been made from flat pieces of PCD or PCBN or their composites. Tools with more complex shapes have generally been made by brazing flat pieces of PCD or PCBN/tungsten carbide composite onto tungsten carbide tool bodies followed by machining the body and composite together to form the desired tool. The limitations that result from using a planar geometry for the PCD layer can readily be appreciated by considering the case of the most widely used machining tool: the twist drill bit.
At present, standard twist drill bits having PCD or PCBN cutting surfaces are mainly of two typ
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Habit Diamond Limited
Howell Daniel W.
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