156 MACHINES FOB CUTTING COAL IN MINES 



Brown's Monitor Coal-Cutter has excited some attention in America. The machine 

 consists of a five horse-power steam-engine driven by steam carried into the mine by 

 a steam-pipe, terminating, however, in a few feet of rubber-hose, which permit of full 

 freedom of motion to the machine. The intention of the proprietors is to employ 

 compressed air in place of steam eventually. The cutting arrangement is an iron rim 

 of four feet in diameter, which has on its periphery movoable steel teeth, placed at 

 points about 12 inches apart. These teeth may be taken out and ground whenever 

 they become dull. This rim lies on small wheels which support it and allow a freo 

 motion, and has cogs on its under surface which gear into cogs on a shaft turned by 

 the engine. By this means the power is applied near the circumference of the wheel, 

 instead of at the centre as in the ordinary circular saw. The principal reason for 

 this arrangement is to get a deeper cut at the coal. The cutter can be put to a depth 

 of 3^ feet, or ths of its whole diameter, whereas the ordinary circular saw can hardly 

 cut to one-half of its diameter. The machine runs on a moveable track, and is fed by 

 means of a screw working in cogs. The track is put down along the side of the coal 

 at the proper distance from it, and when a ciit has been made the whole length, the 

 machine is put on tracks and wheeled to the next ' room,' where the track is laid as 

 before, and so on through the mine. The duty of the machine is calculated to be at 

 about a yard in five minutes. 



The estimate of its economy given by the proprietors is that it saves about 35 cents 

 per ton over the cost of putting out coal by hand labour, which in a mine turning out, 

 say 200 tons a day, amounts to a saving of 70 dollars per day. The first cost of. the 

 machine is very moderate, being only about 800 dollars,. 



Jones's Hand Coal-Cutter. This machine is practically a combination of inclined 

 circular-saws mounted upon a revolving rod, so that the groove cut by each saw runs 

 into the groove cut by the next, thus thoroughly under-cutting a seam. The saws are 

 set on the rod obliquely, and provision is made for retaining them at a proper distance 

 from each other, and in the most suitable position on the rod, the end of which has a 

 -.inn screw-thread cut upon it, by means 



of which it is fastened into the 

 spindle and bearings. Another 

 form of cutting apparatus may be 

 formed from a flat bar of steel, with 

 saw teeth along both of its outer 

 edges, and so twisted that the 

 toothed edges are formed into spirals 

 (Jig. 1420). By this arrangement, 

 which resembles that of Macdcr- 

 mott's rock-perforator, the cutter 

 readily clears itself from the slack 

 which it cuts away. See ROCK-PER- 

 FORATOR. A revolving cutter of this 

 t kind may be worked in two waj-s. 

 It may be caused to sweep in the arc 

 of a circle into and out of the coal, 

 so as to cut out a groove in it, the 

 spindle of the cutter being for that 

 purpose carried by a frame turning upon an axis, such axis being also traversed for- 

 ward from time to time in a line parallel with the face of the coal operated upon. 

 Alternatively the frame carrying the spindle of the cutter may simply be caused to 

 move forward continuously in a line parallel with the face of the coal, in which latter 

 case a groove will be produced of a depth equal to the length of the cutter. But if 

 the cutter is caused to sweep round in the arc of a circle, a groove of any desired 

 depth can be cut, irrespective of the length of the cutter itself. 



Revolving cntters, such as above described, can be driven either by hand-power or 

 by compressed air. In the former case, and when the machine is to be used only for 

 holing or undercutting, the following is proposed as the preferable arrangement. The 

 spindle of the cutter is mounted on bearings in a frame which can turn upon a stud 

 on the bed-plate of the machine. On the under side of this bed-plate are sledge 

 runners to run on rails laid upon the floor of the mine. On the frame which carries 

 the cutter spindle is a toothed arc, into which gears a pinion carried in bearings from 

 the bed-plate. The pinion can be turned by a hand wheel on its spindle, and thus the 

 cutter can be caused to sweep round to and fro in the arc of a circle. Upon the cutter 

 spindle is fixed a bevel pinion gearing into a horizontal bevel wheel, which is con- 

 centric with the stud upon which the frame carrying the cutter is mounted. The 

 horizontal bevel is mounted upon a vertical shaft, upon which is a fly-wheel, and at 

 its upper end a pinion which gears with a bevel wheel, which latter can be driven by 



