Tools and Machinery of the Granite Industry, Part IV

Flute Cutting

Many building and monument columns were fluted (Figure 7). That is, long parallel grooves were cut lengthwise into the column. Prior to the availability of flute-cutting machines, flutes had to be cut by hand-an extremely labor-intensive process. One early flute-cutting machine design was used for sectioned columns (i.e., columns made up of a number of stacked two- to three-foot high sections), and looked like a small version of a gang saw (Figure 8). A column section was secured on its side on a saw cart under five or so saw blades, spaced according to the flute separation. Cuts were made to the proper depth and the column was rotated, and more cuts were made until cuts had been made around the entire column circumference. In a second design, the column section was mounted upright on a stand (Figure 9). There were two driven Carborundum grinding wheels that were moved up and down against the column on posts located on opposite sides. The grinding wheel surface had the profile desired for the fluting grooves. With each up and down travel of the grinding wheels, they were incrementally moved in toward the column center until the proper flute depth was reached. The column was then rotated by one flute spacing, and the process repeated until the entire column circumference had been fluted. A third type of fluting machine was designed as an attachment to a stone-cutting lathe and could flute a monolithic column up to the maximum length handled by the lathe (Figure 10). A driven Carborundum grinding wheel, with the proper grinding surface profile, was mounted on the lathe tool carriage. The column was locked into position in the lathe and the Carborundum wheel was moved back and forth the full length of the column, being incrementally moved in toward the column center for each full-length pass until the proper flute depth had been achieved. The column was then rotated in the lathe by one flute spacing and the process repeated until the entire circumference had been fluted.

Boring

A boring pit, with a flat-belt-driven, vertical-shaft drill, was used to bore arbor holes in press and chocolate rolls (Figure 11). A paper-mill machine used a pair of granite press rolls at the beginning of the paper-making process where the wet pulp was pressed into a sheet and where the superior releasing property of the granite was essential to prevent the wet sheet from sticking to the rolls. At their largest-5 feet in diameter by 40 feet long or about sixty-six tons-press rolls could be massive (Figure 12). In the manufacture of chocolate, beans were ground into a fine slurry using corrugated granite rolls that moved back and forth on a granite bed until the desired degree of fineness was achieved. The finished dimensions of a chocolate roll were 22 ½ inches long by 11 ¼ inches in diameter (Figure 13).

The drill bit was a hollow pipe with a notched cutting edge, using the same rectangular notch configuration as used for the gang-saw blades. As with the gang saws, steel shot abrasive was used. The pits were of various depths to accommodate rolls of various lengths. A roll was set into the pit by an overhead crane (Figure 14). It was bored halfway through and then turned over and the other half was bored. Alignment of the two bores had to be precise. A plumb bob and depth gauge were used to accurately position the roll. The plumb bob was hung from the center of the drill bit and this point was marked on the pit floor. A circle with the diameter of the roll was chalked on the floor with the point as center. The roll was then positioned in this circle and plumed using the depth gauge to ensure that the distance between the roll's top edge and the drill bit was equal all the way around. Boring was a dusty operation so suction equipment was usually installed for this machine.