STONE-CUTTING AND -DRESSING. This is the art of shaping, fitting, smoothing and finishing quarried stone, for use in masonry, foundations of monuments, arches, etc. (For the preliminary steps of taking out the stone see QUARRYING; DRILL AND DRILLING, the drill being one of the most important machines used in quarrying stone). Stone-cutting is more than a mechanical operation; it in volves theoretical and geometrical calcula tions. The study of these is often termed Stercotomy. It involves some knowledge of architecture, and very exact calculations. Sup pose that stones are required to be cut for an arch of 100 feet span and 25 feet rise. The exact curve and angle of each particular stone must be determined geometrically, and drawings made to guide the cutter. In the case of mass ive stone fronts for buildings, in which per haps carvings occur, the design must be first perfected on paper, and sometimes models are made of more intricate parts. When dealing with angles the stone-cutter speaks of a batter of one in 10, meaning that there is a change of angle of one inch in width in 10 inches of length. Or he will specify a one in five rise, indicating the angle above the horizontal.
The primary tools of the stone-cutter are heavy hammers and chisels, the latter being operated with wooden mallets. By striking a stone a number of heavy blows with an edged hammer, along a given line, it will break ap proximately on that line. The more valuable stones, as imported marbles, are sawed, to avoid waste of material. For knocking off projec tions of stones from the quarry, a blunt double faced hammer is used, of perhaps 20 to. 30 pounds weight. Next, for roughly shaping, the face hammer may be employed, this tool having one blunt and one sharp face, and weighing ordinarily 20 to 25 pounds. The cavil, having one blunt and one pyramidal point, is also use ful for rough dressing, and is somewhat lighter than the face hammer. The mason's pick is straight, double pointed, and commonly 18 inches long. It is useful for rough-dressing soft stone. The mason's axe or pean-hammer has two cutting edges, of three to four inches wide. It is useful after the cavil, to prepare
the stone for the patent hammer. The tooth axe has a serrated double head and is not suited to very hard stone. The bush hammer has a head made of a series (as 36) of steel pyramidal points bound together; the points vary in size accord ing to the work to be done. The Crandall and the patent hammer are forms of steel blades or chisels clamped together and used for finishing. Hand hammers, mallets and chisels complete the common tools of the mason for hand dressing. Chisels are named as tooth-chisels, splitting chisels and pitching chisels, the latter being used in forming a straight square edge on a stone. Short-handled, heavy mallets are employed with the chisels. In using a stone chisel, it has to be directed at such an angle as will break off the weaker part of the stone. The knack of this is soon learned, and the experienced stone cutter will remove with each blow almost ex actly what he calculates on doing. For rapid stone-cutting, pneumatic tools are now em ployed. The pneumatic hammer, operated like the familiar pneumatic rivetter, is very speedy in operation. Pneumatic plug drills and bush ing tools are made and operated on the same principle, air pressure supplying force for the blow, and a spring returning the tool to position. Portable surfacing machines are used on large stones, an adjustable arm being swung over the stone, and aligned to the work. Any one of a variety of surfacing tools may be inserted in the tool carrier, and when the compressed air is turned on the tool pounds away at a fixed level under the guidance of the operator, who directs it over the entire surface requiring to be dressed. The stone saw is commonly em ployed for cutting up marble arid sandstone. The cuts made are not quite smooth, and may be rubbed off with a slab and grit, operated by hand or power with water. Consult French,