Loose abrasives

Corundum. Comndum [1302-75-5] (see Aluminum compounds) is a naturally occurring massive crystalline mineral composed of aluminum oxide. It is an impure form of the gems mby and sapphke. Prior to 1900 comndum was an important abrasive for the production of grinding wheels. Today it is mainly employed as a loose abrasive for grinding and polishing optical lenses. Almost all the world s supply of comndum now comes from Africa, primarily from Zimbabwe. 

In this test for transparent plastics, the loss of optical effects is measured when a specimen is exposed to the action of a special abrading wheel. In one type of test the amount of material lost by a specimen is determined when the specimen is exposed to falling abrasive particles or to the action of an abrasive belt. In another test, the loss of gloss due to the dropping of loose abrasive on the specimen is measured. The results produced by the different tests may be of value for research and development work when it is desired to improve a material with respect to one of the test methods. The variables that enter into tests of this type are... 

One distinction between test types is that some use a loose abradant and others use a solid abradant. A loose abrasive powder can be used rather in the manner of a shotblasting machine as a logical way to simulate the action of sand or similar abradants impinging on the plastic in service. Conveyor belts or tank linings are examples of products subject to abrasion by loose materials. A loose abradant can also be used between two sliding surfaces to simulate a contaminant or wear debris. The majority of wear situations involve the plastic moving in contact with another solid material and solid abradants can consist of almost anything. 

Szymanski A., 1966b, Klasyfikacja jakosciowa lu2nego scierniwa (Qualitative classification of loose abrasive), Mechanik, 39 (4), 230-232. 

Finishing Oy the aid of abrasives Bonded abrasives grinding, abrasive belt grinding Loose abrasives barreling, blasting, buffing... 

Boron Carbide. Boron carbide [12069-32-87, B4C, is produced by the reaction of boron oxide and coke in an electric arc furnace (70% B4C) or by that of carbon and boric anhydride in a carbon resistance furnace (80% B4C) (see Boron compounds, refractory BORON compounds). It is primarily used as a loose abrasive for grinding and lapping hard metals, gems, and optics (18).. Although B4C is oxidation-prone, the slow speed of lapping does not generate enough heat to oxidize the abrasive. 

Abrasion resistance is a difficult property to define as well as to measure. It is normally accepted that abrasion resistance depends on the polymer s hardness and resilience, frictional forces, load, and actual area of contact. ASTM D1044 evaluates the resistance of transparent plastics to one kind of surface abrasion by measuring its effects on the transmission of light. Another test method to evaluate abrasion, ASTM D1242, measures the volume lost using two different types of abrasion machines loose abrasion and bonded abrasion. 

Lapping uses loose abrasive particles placed on a soft cloth. 

Free abrasive machining Loose abrasive machining... 

For some applications, this completely eliminates the need for loose abrasive lapping or polishing. The application of ELID grinding to the fabrication of large (150-250 mm in diameter) optical components is also studied. Published data suggest that ELID grinding can be successfully applied fo subsfrates of fhis size regime. 

Loose abrasive nanometric machining. This method uses loose abrasive grits to remove a small amount of materials. It consists of polishing, lapping and honing, etc. 

D. GoUni, S.D. Jacobs, Physics of loose abrasive tnicrogrinding, Appl. Opt. 30 (19) (July 1991). 

Water is used as the abrasive medium (lubricant) for all bonded abrasives in grinding disks and films. In addition to water, fluids and carriers containing oil and alcohol are used most commonly for all loose abrasives in pastes and suspensions. 

ASTMD 1242a Loose abrasive between plastic and plate Simulated 3 - bocfy abrasion... 

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