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A close-up of a segment of a diamond saw blade

A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.

History

In Natural History, Pliny wrote "When an adamas is successfully broken it disintegrates into splinters so small as to be scarcely visible. These are much sought after by engravers of gems and are inserted by them into iron tools because they make hollows in the hardest materials without difficulty."[1]

Advantages

Diamond is one of the hardest natural materials on earth; much harder than corundum and silicon carbide. Diamond also has high strength, good wear resistance, and a low friction coefficient. So when used as an abrasive, it has many obvious advantages over many other common abrasives.

Advantages of diamond grinding tools

Diamond can be used to make grinding tools, which have the following advantages:

Categories

There are thousands of kinds of diamond tools. They can be categorized by their manufacturing methods and their uses.

Categories by manufacturing method

According to their manufacturing methods or bond types, diamond tools can be categorized to the following way:

Categories by use

If categorized by use, there are diamond grinding tools, diamond cutting tools (e.g., diamond coated twist drill bits), diamond drilling tools, diamond sawing tools (e.g., diamond saw blades), diamond drawing dies, etc.

Applications

Applicable materials

Diamond tools are suitable to process the following materials:

As diamonds can react with Fe, Co, Ni, Cr, V under the high temperatures generated in the grinding processes, normally diamond tools are not suitable to process steels, including common steels and various tough alloy steels, while the other superhard tool, cubic boron nitride (CBN) tool, is suitable to process steels. The tools made with common abrasives (e.g. corundum and silicon carbide) can also do the task.

Applied domains

Diamond tools are used in the following domains:

Besides what are listed above, there are also other domains where diamond tools are applied, for example, in medicine, Venezuelan scientist Humberto Fernandez Moran invented the diamond knife for use in delicate surgeries in 1955.

Apart from its use as an abrasive due to its high hardness, diamond is also used to make other products for its many other good properties such as high heat-conductivity, low friction coefficient, high chemical stability, high resistivity and high optical performances. These applications include coatings on bearings and CDs, acting as lens and thermistors, making high-voltage switches and sensors, etc.

Some examples of diamond tools

Diamond dressing tools

Diamond dressers consist of single-point or multipoint tools brazed to a steel shank, and used for the trueing and dressing of grinding wheels. The tools come in several types, including: grit impregnated, blade type, crown type, and disc type. The advantages of multipoint over single-point tools are:

  1. The whole diamond can be used; in a single-point tool, when the point is blunt the diamond must be reset, and after few resettings the diamond is replaced.
  2. Multipoint tools have higher accuracy, especially in form grinding, where blade types are used. Blades consist of elongated diamonds. The thickness is controlled and blades are available in thicknesses from 0.75 to 1.40 millimeters (0.030 to 0.055 in).
  3. Grit-type tools are of a tough grade, and can be used for bench grinders.
  4. Since small points are used, the diamonds have a cutting edge with natural points, unlike single-point tools, which have brutted points.
  5. The cost of multipoint tools is lower, since smaller, less expensive diamonds are used.

PCD cutting tools

Further information on synthetic diamond: Polycrystalline diamond

Polycrystalline diamond (PCD) is formed in a large High Temperature-High Pressure (HT-HP) press, as either a diamond wafer on a backing of carbide, or forming a "vein" of diamond within a carbide wafer or rod.

Most wafers are polished to a mirror finish, then cut with an electrical discharge machining (EDM) tool into smaller, workable segments that are then brazed onto the sawblade, reamer, drill, or other tool. Often they are EDM machined and/or ground an additional time to expose the vein of diamond along the cutting edge. These tools are mostly used for the machining of nonmetallic and nonferrous materials.

The grinding operation is combined with EDM for several reasons. For example, according to Modern Machine Shop,[citation needed] the combination allows a higher material removal rate and is therefore more cost effective. Also, the EDM process slightly affects the surface finish. Grinding is used on the affected area to provide a finer final surface. The Beijing Institute of Electro-Machining[citation needed] attributes a finer shaping and surface geometry to the combination of the two processes into one.

The process itself is accomplished by combining the two elements from each individual process into one grinding wheel. The diamond graphite wheel accomplishes the task of grinding, while the graphite ring around the existing wheel serves as the EDM portion. However, since diamond is not a conductive material, the bonding in the PCD work piece must be ample enough to provide the conductivity necessary for the EDG process to work.

Polycrystalline diamond tools are used extensively in automotive and aerospace industries. They are ideal for speed machining (9000 surface feet per minute or higher) in tough and abrasive aluminum alloys, and high-abrasion processes such as carbon-fiber drilling and ceramics. The diamond cutting edges make them last for extended periods before replacement is needed. High volume processes, tight tolerances, and highly abrasive processes are ideal for diamond tooling.

Polycrystalline diamond compacts

In the late 1970s, General Electric pioneered the technology of polycrystalline diamond compacts (PDCs) as a replacement for natural diamonds in drill bits.[4] PDCs have been used to cut through crystalline rock surfaces for extended periods of time in lab environments, and these capabilities have now been implemented in harsh environments throughout the world.

As of August 2000, the U.S. Department of Energy claimed that nearly one-third of the total footage drilled worldwide is being drilled with PDC bits, with a claimed savings of nearly $100,000 per PDC bit as compared to roller-core bits.[5]

Diamond paste and slurry

Diamond pastes are used for polishing materials that require a mirror finish. They are often used in metallurgical specimens, carbide dies, carbide seals, spectacle glass industry, and for polishing diamonds. Diamond paste is mainly used in industrial requirements for polishing and sharpening metal blades and other metal surfaces. The paste is not just to polish the metal blade but sharpen the cutting edge as well.

Diamond electroplated tools

Diamond powder deposited through electroplating is used to make files (including nail files) and in small grinding applications.

Single point diamond turning tools

Single point diamond turning (SPDT) utilizes a solid, flawless diamond as the cutting edge. The single crystalline diamond can be natural or synthetic, and is sharpened to the desired dimensions by mechanical grinding and polishing. The cutting edge of most diamond tools is sharp to tens of nanometers, making it very effective for cutting non-ferrous materials with high resolution. SPDT is a very accurate machining process, used to create finished aspherical and irregular optics without the need for further polishing after completion. The most accurate machine tool in the world, the LODTM, formerly at Lawrence Livermore National Laboratory, had a profile accuracy estimated at 28 nm, while most machines seek a roughness within that deviation.[6]

SPDT is used for optics, for flat surfaces where both surface finish and unusually high dimensional accuracy are required, and when lapping would be uneconomical or impractical.

Diamond saw blades

For high-speed gas powered cut-off saws, walk-behind saws, handheld grinders, bridge saws, table saws, tile saws, and other types of saws.

Concave blade
For cutting curves in countertops to install sinks or sculpt statues.
Tuck pointers
Thick diamond blades for restoration, involving grinding and replacing mortar.
Crack chasers
Thick V-shaped diamond blades for repairing cracks in concrete.

Diamond tipped grinding cups

Typically used on hand grinders for grinding concrete or stone.

Diamond tipped core bit or holesaw

Hollow steel tube with diamond tipped segments for drilling holes through concrete walls in the construction industry, porcelain tiles or granite worktops in the domestic industry, or also used for sample core extractions in the mining industry.

PCD tool insert

Used in machine tools for machining ceramics and high speed aluminium.

PD tool insert

Used in turning centers for optics and precision surfaces.

Polishing pads

Pads with diamond crystals for polishing marble and other fine stone.

Diamond wire cutting

Wire with diamond crystals for cutting.

Some of the features of Diamond Wire Cutting are:
Non-percussive, fumeless and quiet
Smooth cutting face
Unlimited cutting depth
Horizontal, vertical and angled cutting of circular openings up to 2500mm diameter
Plunge cutting facility which allows blind and rebated openings to be formed
Remote controlled operation for increased safety

Diamond saw chain

For cutting stone, concrete and brick with a special chainsaw.

See also

References

  1. ^ Pliny the Elder. "Natural History". Translated by D.E. Eichholz. Archived from the original on 2017-01-01. Retrieved 2014-05-28.((cite web)): CS1 maint: unfit URL (link)
  2. ^ "Free-Sintering Behaviour of Bronze Powders for Diamond Tools".
  3. ^ Konstanty, Janusz (2013). "Sintered diamond tools: Trends, challenges and prospects". Powder Metallurgy. 56 (3): 184–188. Bibcode:2013PowM...56..184K. doi:10.1179/1743290113Y.0000000058. S2CID 137707986.
  4. ^ Journal of Petroleum Technology. "Legends of Drilling" (PDF). pp. 50–55. Archived from the original (PDF) on 2011-07-26. Retrieved 2010-08-02.
  5. ^ National Renewable Energy Laboratory (August 2000). Diamond-Cutter Drill Bits (PDF) (PDF). United States Department of Energy. p. 2. (DOE/GO 100098-482)
  6. ^ The World's Most Accurate Lathe, Lawrence Livermore National Laboratory, April 2001