Grinding tools

Composites. Another type of electro deposit in commercial use is the composite form, in which insoluble materials are codeposited along with the electro-deposited metal or alloy to produce particular desirable properties. Polytetrafluoroethylene (PTFE) particles are codeposited with nickel to improve lubricity (see Lubrication and lubricants). SiHcon carbide and other hard particles including diamond are co-deposited with nickel to improve wear properties or to make cutting and grinding tools (see Carbides Tool materials). 

The nitrides reviewed here are those which are commonly produced by CVD. They are similar in many respects to the carbides reviewed in Ch. 9. They are hard and wear-resistant and have high melting points and good chemical resistance. They include several of the refractory-metal (interstitial) nitrides and three covalent nitrides those of aluminum, boron, and silicon. Most are important industrial materials and have a number of major applications in cutting and grinding tools, wear surfaces, semiconductors, and others. Their development is proceeding at a rapid pace and CVD is a major factor in their growth. 

A 48-year-old painter is referred for evaluation of recent onset of severe abdominal pains, headaches, and myalgias. For the last week, he has been removing old paint from an iron bridge using grinding tools and a blow torch. His employer states that all the bridge workers are provided with the equivalent of "haz-mat" (hazardous materials) suits. What tests should be carried out Assuming positive test results, what therapy would be appropriate ... 

Figure 28-5 Steel, agate, and boron carbide mortars and pestles. The mortar Is the base and the pestle Is the grinding tool. In regard to boron carbide, the mortar is a hemispheric shell enclosed in a plastic or aluminum body. The pestle has a boron carbide button at the tip of a plastic handle. [Courtesy Thomas Scientific, Swedesboro, NJ, and Spex Industries, Edison, NJ]...

Fig. 9.2. Changes in the mean value of bonding force (N) with the volume of bonding material arising in the grinding tool (Kb) shown as result of static hardness measurement. (After Peklenik, 1960)...

Fig. 9.3. Lines of identical bond hardness dependent on grinding tool composition. (After Peters et a ., 1960)...

Fig. 9.7. Resonance frequency and modulus of elasticity of grinding tools plotted against letter symbols of bond hardness. (After Decneut, 1967)...

Example of commonest precise gradation of grinding tools with Grindo-Sonic (after Moser, 1980)... 

Fig. 9.4. Scratching (a) and Mackensen hardness isolines plotted against the composition of grinding tool. (After Decneut, 19671...

The grinding tools can be classified by their binder phase as resin bonded, ceramic bonded, or metal bonded (sintered or electrodeposited). 

Metal bonded grindstones can be prepared either by powder metallurgy or by electrodeposition. Fabrication of metal-bonded grinding tools by green tape... 

This type of mill is used in wet nanofine grinding. The gap between the conical rotor and the stator of an attrition mill can be varied from 30 to 500 pm. Velocities of up to 35 m s-1 and throughputs of up to several tonnes per hour are possible. Colloid mills are used for the homogenization of liquid-liquid or liquid-solid dispersions. Teeth or abrasive coatings are the main grinding tools. 

Hernandez et al. (1994) used AAS with acid digestion to measure copper, zinc, iron, magnesium and manganese in four South American and 15 African cocoa butters. The much higher levels reported (e.g. iron, 20-50 mg/kg, copper, 11-27 mg/kg) were ascribed to contamination by metals from grinding tools. Principal component analysis could not distinguish between samples from different continents or countries. 

A casehardened steel-grinding tool of precise taper (Fig. 11.7) is fitted to the chuck of an otherwise redundant lathe headstock and rotated at about 60 rev/min. A suspension of No. 400 silicon carbide (carborundum) in a mixture of glycerine and water is applied to the tool and the socket blank held in place with the right hand. 

Prolonged grinding to correct defects in the shape of the blank must not be undertaken, as this will tend to wear the grinding tool. 

The cones are ground into a similar accurately made cone-grinding tool (Fig. 11.8) and again prolonged grinding must be avoided. 

Carbon forming- and moulding-tools and casehardened grinding tools must be provided for each size of joint being made. The standard taper surfaces of these tools must be protected from any type of wear or damage. The success of this method of making standard taper cones and sockets depends on the accuracy of the tools and on the accuracy of the glass blanks. 

Corundum aluminum GRINDING tools. Gems (ruby, sapphire)... 

This image of the Martian rock "Humphrey" shows a hole made by a grinding tool carried on the Mars Exploration Rover Spirit, which landed on Mars on January 4, 2004. The grinding process revealed the inner structure of the rock and produced a sample that could be tested for chemical composition. (NASA/JPL/Photo Researchers, Inc.)... 

Fine particles removed by a cutting or grinding tool. Metal swarf means turnings, borings, chips, wires, clippings, and foil. 

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