454 



passing over this port causes a pressure on the larger area of the valve-piston, which 

 overcomes the constant pressure on the smaller area, and reverses the valve so as to 

 admit compressed air to the opposite end of the main piston. Rotation of the borer 

 is effected by means of a twist bar and ratchet-wheel, the feed or advance is automatic. 

 This machine was employed at Tincroft, and bored 277 holes from the 9th to the 30th 

 of January 1868, or at the rate of 13 holes per 20 hours. In coal sandstone, at 270 

 strokes per minute, the rate of boring was Ifths inch per minute. See Specifications 

 of Patents, November 9, 1866, No. 2,922; January 7, 1867, No. 43; June 10, 1867, 

 No. 1,704. 



Osterkamp's Borer. About four years ago, the machine engineer, Osterkamp of 

 Eschweiler, near Aix-la-Chapelle, Prussia, contrived a light-boring machine, with a 

 steam or air-moved valve. He also added a portable stand, with the object of dis- 

 pensing with the columnar apparatus used in connection with Sach's Borer. The 

 workmen held and directed the machine and also advanced the tool for deepening 

 the hole. 



The weight of a cylinder, having a piston-rod 2^ths and piston 3 inches diameter, 

 was 50 Ibs. "Weight of supporting stand, from 40 to 56 Ibs. 



This machine bored a hole in coal sandstone 1 inch diameter, ^ S 5 ths of an inch deep, 

 in a minute ; and in the same time a second hole J inch diameter, \\ to 1 \ inch. The 

 speed of the machine at 30 Ibs. pressure is about 210 strokes per minute. Length 

 of stroke, 5 inches. Cubic inches of steam or air required per stroke, 40 or 43 strokes 

 per cubic foot. Pressure for blow 135 Ibs., for returning piston 75 Ibs. For par- 

 ticulars and illustration of Borer, see Specification, No. 1,466, A.D. 1870. 



The McKcan Rock-drill, This rock-drill is worked either by steam or compressed 

 air, and can bo adjusted to any required position, so that holes may be drilled at any 



197 



angle, the machine working with eqtml facility in every direction. The valve is 

 adapted to deliver from 400 to 1,000 blows per minute, while the stroke of the piston 

 and fall of the cutter bar is only 1\ inches or 3 inches ; the shock to the cutter bar and 

 piston when striking the rock is cushioned by the steam or air in the cylinder. 



The cylinder, valve-chest, and frame for carrying the guides and bearings for the 

 piston, valve-rods and other parts of the machine are cast in one piece. The per- 

 cussion cylinder is marked a and the valve-chest b ; the valve seating is formed of a 

 small cylinder c placed within the valve-chest situate on one side of the cylinder a. 

 The valve d is cylindrical, its axis is parallel to that of the piston-rod, and on one 

 side there is formed a projecting curved face d', forming the working part of the valve 

 which alternately covers and uncovers the admission ports e e, that extend the whole 

 length of the valve-chest c. The exhaust port is formed between the admission ports, 

 and opens into the centre of the cylindrical valve. 



The oscillating movement required for actuating the valve is given by the spindle 

 through the key d 3 , and the groove. At the bottom of the valve a shoulder d 1 is also 

 formed, fitting tightly in the cylinder. By this means the escape of steam or air is 

 prevented, and sufficient friction is produced to avoid any excessive motion of the 

 valve from the action of the tappets which actuate the spindle. These tappets aro 

 shown at 1 1', where it will bo seen that they are attached to a sleeve fastened upon 

 the valve spindle, and at such an angle on each side of the centre line passing through 

 the valve spindle, and piston-rod, that they may bo struck by the enlarged portions of 

 the latter k l k' 1 . The piston /is formed of steel, in one piece with the piston-rod 

 ff', and the tool holder g l . Grooves aro formed in tho piston, as shown at /', to 

 receive metallic piston-rings. The rod in advance of tho piston is of a diameter 

 larger than that at the rear, in order that sufficient strength may be obtained for 



