This machine is primarily suited for the heaviest work and the deepest cuts, in open quarries of limestone, sandstone, slate and other materials, where the output is in dimension stone. In this service it has found its greatest field in making the long, deep, longitudinal cuts which are preliminary to further breaking by the plug and feather method. It has found another valuable field of application in certain classes of heavy contracting work, such as rock excavation for canals and reservoirs.
The channeling machine is mounted on a self-propelling carriage or truck which runs on a track from 10 to 30 feet in length. If it has but one cylinder drill it is called a simplex machine; if two, a duplex machine. The stroke is about 10 inches and 250 blows are delivered per minute. The bits are usually used in gangs of three or five, set at varying angles, if the stone is uniform in texture. If uneven a single bit is used. In the usual quarrying operations the stone is channeled on 'two sides of a rec tangle and then split off by wedges. In some instances it is channeled on three sides and also undercut at the bottom by a horizontal chan neler called a °gadder?) The average cut with these channeling machines is from 8 to 16 feet in depth, depending upon the nature of the stone. The gauge or width of the cut will depend upon the final depth sought. It may be from one and one-half to four inc.Ms at the start, reducing to a width of one and one eighth inches with the last steels. The length of the channel is limited only by the length of track which can be used. Cutting speeds vary with the quality of rock and the handling of the machine. There are cases an record Where the machine channeled faces ag.gregating 100 square feet in 10 hours in oolitic limestone, during part of which time over 100 square feet per hour was cut. In Ohio sandstone of me dium hardness, 260, 280 and 300 square feet per day of 10 hours have been channeled and these rates are being maintained as an average by the month. The average cost in this case runs from two and one-half cents to three and one-half cents per square foot cut: When channeling is done on two sides of a block the bulk of stone taken out is about three and one-third cubic feet for each square foot of face channeled. Where the machine is used on three sides. the average product is two and one-half cubic feet per square foot of channeling. The extra cost of machine work is soon recouped, in blasting out rough rock fully 20 per cent of the bulk is lost, being outside of the dimensions, and 'hence not paid for.
Helicoidal Sawa—Experiments with the so-called helicoidal saw for quarrying the softer rocks, as limestone and marble, have met with considerable success in the larger limestone quarries of the Middle West. The large amount of labor necessary for putting the saw isigo sition and the waste involved in cutting out the corners in which the pulleys are run are weighty disadvantages, but where long cuts can be made —30 to 100 •feet, this usawa is very profitable. The °saw)) consists of a. three
strand twisted iron-wire rope, generally one fourth of an inch in diameter, running over sliding and fed continually with abra sive material such as sand or grains of chilled iron. It is necessary in working on bedrock to sink well holes for the 20-inch pulleys on which the saw runs. It is more commonly used for making vertical cuts. With a new thin model of pulley wheels the use of this saw is increasing.
After the stone is removed from the quarry bed it is worked into the desired shape and size by.a process dependent largely upon the hard ness of the stone. Formerly a block after being reduced to an approximately rectangular form by means of hand plug and feather splitting was still further reduced by pitching tools, followed when necessary by such implements as the point, ax, peak-hammer and bush-hammer. Pneumatic tools are gradually replacing these hand imple ments. Pneumatic surfacing machines, lathes and planers are now in use at the larger quarries. Indeed, the production of cylindrical columns by the old hand method has been al most entirely superseded by the use of lathes similar to those used in turning metals. Except on the harder stone, like granite and quartzite, saws are extensively used for dividing up ma terial into rectangular masses and slabs where smooth, even surfaces are desired.
Electricity in The quarrying industry to-day constitutes an important field for the application of electric current, and the sub ject has become so important as to create a literature and a technology of its own, for many of the problems involved are such as do not arise in connection with other work. The flexi bility of electric circuits and the general adapt ability of electric power have led to a wide range of applications, some of which are still in the experimental stage. Motors and other necessary equipment have been designed for special requirements. Beginning with a small direct current station and leading up to a com plete high tension transmission and converting system, the use of electricity in mining and quarrying is very similar to its application to street railway work. Special motors for the equipment of mine locomotives have been de signed to meet the peculiar conditions con fronted in mining and quarry work. A recent application is that of the gathering locomotive which is to a great extent replacing animal haul age completely. This locomotive is equipped with a reel and cable, supplying power to it when gathering cars from rooms where no trolley is installed and where wooden rails are used. Standard motors are applicable to and are largely used on hoists, ventilating fans and drainage pumps.