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Tools and Machinery of the Granite Industry, Part III

Chronicle of the Early American Industries Association, Inc., The, Dec 2006 by Wood, Paul

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Polishers were used on surfaces prepared by the gang saw and the surfacing machine. Polishing took place in three stages: initial grinding with sand or iron shot; closing up with emery or Carborundum; and buffing with tin or zinc oxide. Abrasive consumption for the three polishing stages would be approximately: ½a to 1 pound per square foot of no. 3 iron shot; ¼ pound per square foot of no. 80 Carborundum; and 1/40 pound per square foot of tin oxide. A variety of polishing wheels were used depending on the polishing stage and abrasive used: broken scroll, cast scroll, emery ring, concentric ring, contained abrasive brick, rope buffer, coco mat, and felt buffer (Figure 31). A typical 18-inch polishing wheel was designed to rotate at 200 rpm, required a 10 HP engine and, with an experienced operator, could polish thirty to forty square feet in an eight-hour day. Often the first-stage polishers had an abrasive pump that fed abrasive to the polishing wheel which allowed faster polishing so this machine could supply several other machines that were doing the closing up and buffing. During the last stage, buffing, the polishers used were first a very fine wheel and then a felt buffing wheel. The felt buffing wheel was a cast iron wheel with slots into which pieces of felt were inserted and wedged in place with wood pins.

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Bed setters prepared multiple stones in a level bed so that they could be simultaneously polished by a large, gate-type polisher (Figure 32). (Polishing of an entire slab greatly simplified the setting process.) Bed setting required only relatively simple tools but did involve considerable skill and experience to do the job right. It was a dirty job and bed setters typically wore overalls. First, a stone was blocked with wooden blocks and wedges. A level was used in two perpendicular directions to insure a level surface. An iron pry bar was used to make the necessary adjustments. As additional stones were added, they were blocked and made level with the first stone and any other adjacent stones. A hatchet was used to drive wedges between the stones. Next, paper was stuffed into the cracks between the stones. Using a wooden paddle, the remaining cracks were filled with plaster level with the top of the stones. The plaster both helped to hold the stones in place and also to keep the abrasive on the surface and in action. Prior to final buffing, the top quarter inch of plaster was removed so it would not contaminate the buffer. Later designs of the gate-type polisher, for example those manufactured by W A. Lane Co. of Montpelier, Vermont, in the 1890s, included an arm that could reach two beds. Thus, while one bed was being polished, the other was being set up so that the polisher could be in continuous operation.

The vertical polishing machine manufactured by the Concord Axle Co. and used circa 1890, was suspended from an overhead beam (Figure 33). It had a ten- to twenty-foot-long vertical main shaft with bevel driving gears and a universal joint at its top. The polishing wheel was attached to the bottom of the shaft with a second universal joint. The shaft and polishing wheel could be raised and lowered and had a counterbalancing weight to make movement easy. This polisher had many degrees of freedom-the polishing wheel could be moved to any point on a horizontal plane and could be raised and lowered. The polishing wheel could also be tilted to any angle. This flexibility allowed the vertical polisher to work on curved as well as horizontal or slanted flat surfaces. In 1896-97, H. H. Harvey was selling a vertical polishing machine for $100.

Tools and Machinery of the Granite Industry, Part III

Chronicle of the Early American Industries Association, Inc., The, Dec 2006 by Wood, Paul

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