Sand-grinder

Hochberg and Bosse of E. I. DuPont de Nemours, with the "Sand Grinder" patent (6) took the idea of using small spherical media in the form of Ottawa silica sand with an average diameter of. 7 mm to a practical machine. Later glass, ceramic and steel media materials would become available and sand grinders would evolve into bead mills, shot mills, and small media mills. (Figure )... 

The original sand grinder used a central shaft with a series of annual rings which spin between 1220 and 2k00 rpm to achieve a peripheral disc velocity of about 2000 ft./min. or 10 meters/ sec. (Figure k) Unlike the ball mill or Attritor, this media is accelerated 200 - 300 Q s by this centrifugal force as compared to 1 G in the ball mill. 

The vertical sand grinder literature (.7) established that media and slurry were to maintain equal volumes in the milling chamber for optimum interaction. 

Hochberg, S. Bosse D, "Agitator Ball Mill - Sand Grinding Process, U.S. Patent 2 855 156 Nov. 1958 Bosse, D. "Pigmented Systems and Application of the Sand Grinder" Purdue Univ. Short Course March 1959. Daniel, F. "Determination of Mill Base Composition for High Speed Dispersers" Jour, of Paint Technology... 

Sand grinding n. Process of dispersing pigments in the sand grinder. 

Properly graded sanding with appropriate sandpapers is a prerequisite for a satisfactory wood surface. Industrially, sanding is performed on cylindrical abrasive-belt machines or automatic grinders, followed by brushing and suction to remove abrasive dust. 

An industry standard scarf repair first involves removal of topcoat and primer and then using a hand-held pneumatic router or grinder to machine the damaged portion of the laminate into a circular shape. The sides of the circular cutaway must then be machined to a taper at the required angle. Two approaches can be employed, either stepped or scarfed. The scarfed joint is theoretically superior (better stress distribution) but little difference is seen in practice. The joint face is sanded to a constant... 

Sanding is the greatest source of lead dust. Electric sanders, grinders, or planes are sometimes used after scraping to remove any paint that scraping did not get off. Although this method is simple and inexpensive, it is not recommended because it creates large amounts of toxic lead dust, unless a vacuum attachment connected to a HEPA-vac is used with the Sander. 

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