Diamond tool
From Wikipedia, the free encyclopedia
 |
It has been suggested that diamond blade be merged into this article or section. (Discuss) |
A diamond tool is a cutting tool which contains diamond segments bonded to a base material, for cutting through a wide variety of non-ferrous materials. The segments are composed of diamond crystals and powder metal which form the bond, or 'matrix', of the segments.
When used for grinding, 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 workpiece 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 grinding or sawing 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.
Contents |
[edit] Categories of Diamond Tools
[edit] Diamond Dressing Tools
Diamond dressers, which consist of single point or multipoint brazed to a steel shank and are used for truing and dressing of grinding wheels, mostly in the automobile industry. After enormous research, the shape and sizes were invented like Grit impregnated, Blade type, Crown type, disc type etc. The advantages of multi point over single point are,
- The whole diamond can be used unlike single point when the point is blunt you have to reset and after few resetting the diamond is wasted.
- More accuracy specially in form grinding, blade types are used. Blades consists of elongated diamonds and the thickness is controlled and are available from 0.75 mm to 1.40 mm.
- Grit type tools are of tough grade and can even use for bench grinders.
- Since small points are used, these diamonds are of cutting edge with natural points unlike single points are brutted points.
- Cost will also be very low since small diamonds are used. Diamond value varies more according to size.
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
Polycrystalline diamond(referred to as 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 Electric Discharge Machine (EDM) 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. Today these tools are mostly used for machining of nonmetallic and nonferrous materials.
The grinding operation is combined with EDM for several reasons. For example, according to Modern Machine Shop, 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 zone to remove the effected area and provide a finer final surface. Along the same lines, Bejing Institute of Electro-Machining attributes a finer shaping and surface geometry to the compilation of the two processes into one.
The process itself is accomplished by combining the two elements each individual process into one 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 generate the conductivity necessary for the EDG process to work.
[edit] Diamond Paste and Slurry
Diamond pastes are used for polishing materials that require a mirror finish. Often used in metallurgical specimens. Also used widely in carbide dies, carbide seals, spectacle glass industry and also for polishing of diamonds.
[edit] Diamond electroplated tools
Diamond powder deposited through electroplating are used in form of files, or small grinding applications. It has also found a new use of making nail files for nails.
[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 very hard 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.
- For more detailed explaination of how to use a diamond drilling holesaws see Diamond_drilling_porcelain
[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.
Other diamond tools
- Concave blade: 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 cutting: wire with diamond crystals for cutting.
