Grinders and Brazers of Hard Metal and Stellite

Saw blades tipped with hard metal (<10% cobalt, 90% tungsten carbide) or stellite (60% cobalt, 30% chromium, 10% tungsten) are used mainly in the mechanical wood-processing industry. There is considerable exposure to cobalt in the manufacture and maintenance of the blades (Stebbins et al. 1992; Teschke et al. 1995; Linnainmaa et al. 1996), even though it is less than in hard-metal production (Koponen et al. 1982; Sprince et al. 1988; Meyer-Bisch et al. 1989; Kumagai et al. 1996). The workers grinding and brazing blades can be exposed to high levels of airborne cobalt, while concentrations of tungsten, chromium, cadmium, silver and nickel in the air are low (Linnainmaa et al. 1996). According to Linnainmaa (1995), cobalt is easily dissolved in grinding coolants, especially during the first weeks of use and, therefore, they should be changed at least monthly. Workers’ exposure to cobalt can also be reduced by improving skin protection and personal hygiene in workplaces (Linnainmaa and Kiilunen 1997).