Tools and Machinery of the Granite Industry, Part III

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

As early as the 1860s, H. & J. L. Young of New York City designed and manufactured a circular saw with embedded diamonds. In the early 1890s, the French company M.M. d'Aspine Achard manufactured a circular saw with one-half-carat, rough, black diamonds ($5-$10 each) set in the circumference. Achard's key contribution was a new setting technique in which the diamonds were retained even with the high blade edge speed-much higher than gang saw blades. The diamond saw yielded a very smooth sawn surface that could be polished without any intermediate dressing. It was estimated that the sawing rate was twenty to fifty times that of a gang saw using sand or iron shot. By the turn of the twentieth century, F. R. Patch Manufacturing Co. of Rutland, Vermont, was manufacturing a gantry diamond circular saw with a 300-pound, 6 ½-foot diameter blade that rotated at 500 rpm (Figure 14). The company touted its highly reliable diamond setting technique and promised only the best quality (hard) diamond borts. Now, computer-controlled circular saws with up to thirteen-foot diameter diamond segment edged blades carry out the large-scale initial sawing of the quarry saw blocks. The diamond segments are set onto the blade with a brazing technique. A twelve-foot diameter blade has about 160 diamond segments and can saw fifteen square feet per hour. The saw moves over a stationary saw block with a continuous flow of water on the blade for cooling, to reduce airborne dust and to flush out the cuttings. These saws run twenty-four hours per day, unattended during nights and weekends. The computer notifies the operator by telephone at home if there is any problem.

There are now available a wide variety of diamond saws, some hand-held and some supported on rails, arms, or gantries. Examples include horizontal saw, gantry saw, vertical curve saw, slab saw, radial arm saw, rail saw, chain saw, cut off saw, and band saw.

Lifting and Moving Granite Within and Between the Sheds

Although occasionally a boom derrick similar to those used in the quarry might be used inside a round shed, it was the straight shed with its overhead traveling bridge crane that revolutionized the lifting and movement of granite in the shed. The manually powered, overhead bridge crane with a chain fall hoist was introduced into the American granite industry in the 1880s, apparently having originated in Scotland. The overhead traveling bridge crane consisted of a bridge that spanned the width of the shed (thirty to forty feet) and ran on tracks that went the entire length of the shed-one track on each side of the shed. A trolley ran back and forth on tracks that went the length of the bridge. A fall rope and hook was suspended from the trolley and was raised and lowered by a hoist on the trolley. Thus, the hook could reach any location on the shed floor. The Lane Manufacturing Co. of Montpelier, Vermont, was one of the early manufacturers of traveling bridge cranes. Their initial design was a "flying rope" crane, powered by a continuously moving endless loop of hemp rope driven by a steam engine or electric motor (Figure 15). The rope loop ran the entire length of the shed on sheaves and also ran across the bridge to power the trolley. The operator sat on the trolley and controlled the crane through levers and foot pedals, looking down through a grating to see the hook and lumper. It is said that many a longtime crane operator had a bent neck from constantly looking down through the grating. A long loop of rope moving at high speed was quite dangerous. In one recorded case, the rope came offits sheaves and decapitated a worker! These cranes were soon replaced by electric cranes