Diamond tool
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A diamond tool is a cutting tool which contains diamond segments for cutting through a wide variety of materials which other cutting tools cannot. The segments are composed of diamond crystals and powder metal which form the bond, or 'matrix', of the segments.
The bond is one of the prime factors when selecting which tool to use for cutting a specific material depending on how hard, or abrasive, the material is. The bond is what decides the rate at which the metallic powders wear down and expose new diamond crystals at the surface to maintain what would be considered a “sharp” edge.
Diamonds should not be used for cutting steel or iron, as carbon will dissolve into the workpeice and lead to tool wear and work hardening. Three other materials are used for cutting steels where diamond would be used: Cubic boron nitride (cBN, the second hardest material known), aluminum oxide, and silicon nitride tooling may be used.
For cutting hard materials, a diamond blade with a soft bond would be needed. This means the metallic powders in the segments (teeth) of the diamond blade wear fast enough to release old, dull crystals, exposing new diamond at the edges to continue cutting efficiently. Inversely, to cut a soft abrasive material like asphalt or freshly poured concrete, you would need to use a diamond blade with a hard bond so that the segments do not wear down prematurely and the blade is not put to waste. Diamond is especially suited to cut highly abrasive materials, such as ceramics.
The diamonds used in these tools are synthetic or natural industrial diamond of different grain sizes and shapes.
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[edit] Catagories of Diamond Tools
[edit] Grinding Abrasion
Many diamond tools don’t cut like a knife or saw blade, instead they grind. They usually have segments, or teeth, welded to the “cutting” edge of the tool which contain exposed diamond crystals for grinding.
For example, with a diamond blade, the saw operator will push the blade through the material. The blade will begin to cut through the material and the material being cut will begin the wearing process of the diamond blade, at the rate of which the blade advances or the depth at which is being cut. The exposed diamonds will break into smaller pieces when cutting. Hard, dense materials will fracture the diamonds faster. As this happens, the material being cut also wears down the metal bond through abrasion. Highly abrasive materials will wear the bond faster, exposing new diamond crystals to continue cutting.
[edit] PCD Cutting Tools
This would be similar to most other cutting tools. Polycrystaline diamond (referred to as PCD) is formed in a large High Temperature-High Pressure (HT-HP) press. Forming an industural 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 Electric Discharge Machine (EDM) into smaller workable segements that are brazed onto the sawblade, reamer, drill or other tool. Often they are EDM machined and/or ground an additional time to finished specifiactions.
The veined products are usually ground to expose the vein of diamond along a cutting edge. Such as a drill, reamer, or insert.
[edit] SPDT Tools
SPDT, or Single Point Diamond Turning, utilizes a solid, flawless diamond as the cutting edge. SPDT is a very accurate machine process used to create finished aspherical and irregular optics without the need for further polishing. The most accurate machine tool in the world, the LODTM at Lawrence Livermore National Labs, has a profile accuracy estimated at 23 nanometers.
[edit] Differences in method
PCD tools are used extensively in automotive and aerospace industries. They are ideal for speed (9000+ SFM) machining 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 without having to shut down processes to replace tooling. High volume processes, tight tolerances, and highly abrasive processes are ideal for diamond tooling.
SPDT is used for optics, and for flat surfaces where both surface finish and irregularly high dimensional accuracy are required when lapping would be uneconomical or impractical.
The grinding method is ideal for materials that do not cut but are ground; stone, cement, carbides are all difficult to process normally. Often this makes a diamond abrasion method necessary.
[edit] Uses
Diamond-edged tools are commonly used for cutting a wide variety of construction materials, including reinforced and cured concrete, all types of brick and cinder blocks, dense metals, rebar, asphalt, granite, marble, travertine, porcelain, and many other types of materials which cannot be cut with ordinary cutting tools.
[edit] Types
- 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.
- Diamond tipped grinding cups: Used commonly 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 ceramics and high speed aluminum machining.
- SPD tool insert: Used in turning centers for optics and precision surfaces.
[edit] Other diamond tools
- Concave blades: For cutting curves in countertops to install sinks or sculpt statues.
- TuckPointers: Thick diamond blades for restoration - grinding and replacing mortar.
- Crack chasers: Thick V-shaped diamond blades for repairing cracks in concrete.
- Polishing pads: Pads with diamond crystals for polishing marble and other fine stone.
- Diamond wire: wire with diamond crystals for cutting.
