Diamond tools

L. Small, Hardness Theory andPractice Service Diamond Tool Co., 1960. 

Siatered polycrystaUine diamoad tools are much more expeasive than conventional cemented-carbide or ceramic tools because of the high cost of the processiag technique and the finishing methods used. Diamond tools, however, are economical on an overaH-cost-per-part basis for certain appHcations because of long life and iacreased productivity. 

To overcome this drawback, capillary sectorial fibres (Figure 11) were fabricated31. In this case part of the preform ground to the designed shape was inserted into a circularly symmetric silica tube and drawn. The active length of the sensor is defined by the distance between the input and output of the analyte produced in the capillary wall by special diamond tools. Despite promising results achieved, difficulties in the application of sensitive layers on the core surface remain a drawback of this kind of fibres and the... 

The modern material Ebonex is a mixture of substoichiometric titanium oxides Ti40y, TisOg. .. Tin02n-i ( Magneli phases [32]). It offers a unique combination of electrical conductivity and corrosion resistance. Primarily, Ebonex is produced as a powder. As is usual for ceramics, the ready-formed material is hard and brittle, the possibilities of machining are restricted (diamond tools). 

Carbon and glass fibres are very abrasive and quickly wear away high-speed steel tools. For intensive use, carbide or diamond tools are preferable. 

Natural single-crystal diamond and carbonado can now be replaced in many industrial uses by sintered diamond tool blanks. Such tool blanks are available in disks and cores. The disks, or sectors of disks, consist of a thin (0.5—1.5 mm) layer of sintered diamond up to about 50 mm diameter on a cemented tungsten carbide-base block about 3—6 mm thick. Using diamond abrasive, such blanks can be formed into cutting tools of various shapes. Typical tool blanks are shown in Figure 9. The wire dies have diamond cores up to 10 mm in diameter and 10 mm in length, which are encased in a cemented tungsten carbide sleeve up to 25 mm in diameter. 

The effects of high hardness are important in many fields. Abrasives are used to form and polish many substances. Diamonds are an important mineral component in cutting tools for the manufacturing of metals and other substances, forming dies for the drawing of wires, and for cutting cores in oil wells and mineral exploration. Emery - a variety of corundum, is used in many abrasive products that do not require the hardness (or expense) of diamond tools. Garnets were used as an abrasive in sandpaper. Talc is an extremely soft mineral that has been used in bath powders (talcum powder). 

Knoop F., Peters C. G., Emerson W. B., 1939, A sensitive pyramidal-diamond tool for indentation measurements, J. Research. NBS, 23, 39-61. 

Limited supply, increasing demand, and high cost have led to an intense search for an alternative, dependable source of diamond. This search led to the high pressure (ca 5 GPa (0.5 x 106 psi)), high temperature (ca 1500°C) (HP—HT) synthesis of diamond from graphite in the mid-1950s (153—155) in the presence of a catalyst—solvent material, eg, Ni or Fe, and the subsequent development of polycrystalline sintered diamond tools in the late 1960s (156). 

There are several ways of measuring indentation, but they differ only in the type of equipment used. Basically, they all measure the size of indentation produced by a hardened steel or diamond tool under a defined pressure. A durometer is an instrument for measuring hardness by pressing a needlelike instrument into the specimen. Durometers are available in several scales for measuring relatively hard, brittle materials to soft elastomers. The two types appropriate for most cured adhesives and sealants are the Shore Type A and Shore Type D. ASTM C 661 offers a method for measuring indentation hardness of elastomeric-type sealants. 

---