Grit size

Grinder Variables. The quaUty of pulp depends on wood species, moisture content, and grinder variables such as peripheral stone speed, grit size and number per unit area, and pattern on the stone surface. Process variables that affect pulp quaUty include grinding pressure pit consistency, ie, consistency in the space immediately below the grinder (2—6%) and temperature (40—80°C). The combination of moisture and raised temperature tends to soften the lignin. 

Dental abrasives can be classified either according to their use or according to the degree of their abiUty to abrade (see Dentifrices). The use classification, adopted for the ADA specification no. 37 for powdered dental abrasive materials, is based on removal of stain from natural teeth or on restorations of all types. Several abrasives are used in dentistry in a variety of grit sizes and shapes. 

Grinding wheels are by far the most important bonded abrasive product both in production volume and utility. They are produced in grit sizes ranging from 4, for steel mill snagging wheels, to 1200, for polishing the surface of rotogravure rolls. 

Figure 3. Dissimilar grit-size dependence of diamond nucleation densities on substrate surface pretreatments, (a) Nucleation density versus inverse abrasive paste mean-size used in polishing pretreatment.(b) Nucleation density versus single-particle mean-size used in ultrasounding pretreatment solid squares Ref. 317, blank squares Ref. 322, solid circles Ref. 323. (Reproduced with permission.)...

P. Ascarelli, and S. Fontana, Dissimilar grit-size dependence of the diamond nucleation density on substrate surface pretreatments, Appl. Surf. Sci., 64(4) 307-311 (1993)... 

The best method for close tolerance finishing is probably by sanding or grinding at about 20 m/s speed for 80-240 grit size paper. If perfectly flat surfaces are required, sandpaper can be taped or glued onto a float glass piece, and the specimen sandpapered on this surface. 

Up to 30% porosity improves chip clearance independent of grit size... 

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