.'<tE UtiKARl^ otP 1»/1- A Weekly Jourral of the Minini; and Mineral Industri^n largest Circulation of Any Mining and Metal Journal in the World Dredge of Gold Canyon Dredging Co., Near Silver City, Nevada Concentrating by Roughing—II By E.S. Wiard * The Transportation of Dredge Material By George J. Young The Black Lake Asbestos Area By Wynant D. Hubbard A description of the details The subject of licensing min¬ covering the sinking of the ing engineers has been under Water Lily Shaft at Eureka, discussion by the Mining and Utah, is given on page 376. Metallurgical Society. A Information required by rules report of the Committee ap¬ governing the Gold Medal pointed to analyze the replies award for breaking the World’s received to a questionnaire Shaft Sinking Record has been appears this week under submitted to the Committee. “Echoes from the Fraternity.” ( In all Parts of the World S-A Belt Conveyors are carrying heavy loads with a method¬ ical regularity which is possible only with equipment which is correctly designed and well built. Unit Ball-Bearing Carriers permit that smooth, easy motion which saves power and belt-wear. “S"A Belt Conveyors^^ Catalog No. 26. This interesting catalog pertaining to conveyor design and equip¬ ment should be on your desk. Stephens-Adamson Mfg. Co. Aurora, Illinois j J. E. SPURR F. E. WORMSER Editor Engineering and W. N. P. REED G. J. YOUNG Western Editor Assistant Editors D. E. A. CHARLTON BENJAMIN L. MILLER Managing Editor Mining Journal ROBERT M. HAIG A. H. HUBBELL News Editor J. VOLNEY LEWIS E. H. ROBIE A Weekly Journal of the Mining and Mineral Industries Special Metallurgical Editor METALS NON-METALS PETROLEUM Consulting Editors Volume 112 New York, September 3,1921 Number 10 The Progress of Rock Drill Bits but the mining industries have been slow to take full During the last several years a number of advantage of the splendid work done for their benefit. important articles have been contributed to the There has been prompt acceptance of drilling ma¬ teqhnical and Institute publications on the subject of chines of different types, but apparently only a small rock drill bits and drill steel. Probably the most im¬ proportion of the total number of mining companies portant principle described is exemplified by the double- have taken advantage of the double-taper cross-bit and tapered rock drill bits. The Carr bit was, according double-arc bit. to an expert with whom we had the pleasure of dis¬ We can understand how efficient salesmanship can cussing the subject, the first bit in which the double¬ keep the mechanical drilling equipment up to the min¬ taper principle was utilized. Although incorporated in ute. The same force has contributed to the mechanical- the design of the bit and made use of, its importance izing of the drill-sharpening shop. Drill sharpeners was probably not recognized for some time. and oil furnaces are now conspicuously employed. By Briefiy, the double-taper bit is a cross-bit with all of their help a conscientious blacksmith can turn out bits the cutting edges lying in one plane and the wings conforming to accurate sizes and shapes. The technique brought back from the cutting edges within a conical has been well worked out, but how thoroughly does surface, making an angle with the axis of the drill mining practice take advantage of the facilities thus varying from a minimum of 5 deg. to a maximum of afforded ? 7 deg. This conical surface is brought back from the From our limited inquiry it would appear that the cutting edges for a distance of f in., and from this more progressive companies are keenly alive to the point the wings fall within a 14-deg. cone to the drill economies resulting from utilizing to the fullest meas¬ steel. The result is that a bit is produced which has ure proper mechanical upkeep of drilling machines, excellent reaming qualities and which permits, in many thorough lubrication by means of carefully selected instances, a change from. the customary it-in. to a lubricants, and the use of the best grades of drill steel *-in. reduction in diameter for follower bits. It is accurately sharpened and hardened. We do not believe thus possible to diminish the size of starting bits, with that the rank and file have, on the other hand, realized the result that there is a perceptible gain in drilling fully the economic advantage of doing this. Standards speed and a smaller total of energy required in over¬ can be worked out for small as well as for larger coming the cohesion of the rock particles, as a smaller organizations. volume of rock is removed in drilling a hole of given The economy resulting from consistent study of depth. Manufacturers of drill-sharpening appliances details of mining is in the aggregate large. Isolation have been chiefly responsible for the double-taper cross¬ and excessive conservatism are probably in a measure bit, and the necessary appliances for its convenient responsible for the slowness to take advantage of the manufacture at mines have been pretty thoroughly progress that is being made. These can, however, be developed. overcome by consistent study of technical publications One company has pioneered a step further and de¬ and by visiting mining districts where variations in veloped what is termed a “double-arc” bit. This is mining practice can be observed. similar in principle to the double-taper cross-bit, with the difference that the cutting edges are curved in the Offending Latin Americans form of two arcs connected by a short bridge at the There is a provincialism which exhibits it¬ center. This bit has been tried out and has been found self in a racial or sectional bitterness and deprecia¬ to give excellent results. According to our information, tion of one people by another. We find it rampant in it has not been patented and has been given freely to Europe, whether in Germany, France or England—a the mining industry. There are thus available, in addi¬ narrow snobbery that reminds one of the horizons of tion to the Carr bit, two well-developed rock drill bits, our childhood. Some Americans who are familiar with the cross-bit and the double-arc bit, both of the double¬ Latin-American countries complain that a certain type taper design. The Carr bit is, both in speed of drilling of superficial Americans, writers and otherwise, make and stamina, as satisfactory for hard rock drilling as patronizing statements concerning South America the cross-bit and double-arc bit. It is, however, harder which have not even the merit of being true, to say to make and to maintain. Of the three bits, probably nothing of being courteous. We have before us a letter no one has special advantage in drilling as compared from such a man who speaks concerning an article in with the others. The double-taper cross-bit is the most the Century Magazine, criticising the City of Santiago, used, principally because it is easy to form and main¬ Chile. Concerning this he says: tain. It is important, however, to bear in mind in any “It is time that our Government took steps to discourage discussion on rock drill bits that there is no best type this line of advertising for the U. S A. There are a lot of of bit for dll kinds of rock. people in the United States with nothing above their shoul¬ The significant features in modern rock drill bits ders who are continually making derogatory statements have been described in the Journal and elsewhere, about the Latin-American countries, while a few of us who 361 362 Engineering and Mining Journal Vol. 112, No. 10 are living here are trying to show these people we are right, cessful, but were discontinued after a fire. The work¬ and endeavoring to promote better relations between the ing of waste dump and old stope fills continued, but two countries. was probably unprofitable. Stories about large ton¬ “A great many of the statements in the article mentioned are greatly exaggerated, and the entire article is productive nages of low-grade ores in the area north of and of no good whatever. It says the streets of Santiago re¬ adjoining the three mines mentioned were current, but semble White Chapel, London; this is plain libel, the streets no mining was done to check them up. Alex Wise saw of Santiago compare in cleanliness very favorably with the an opportunity here and proceeded to get financial streets of many of our large cities in the United States. assistance. The result of his and Herbert Humphries’ It says the streets are badly paved; this is true in a few preliminary work was the development of a low-grade cases, but generally speaking the streets of Santiago com¬ pare very favorably with cities of like size in the United orebody close to surface in the midst of the old work¬ States. It says the Cerro Santa Lucia is the only place ings. This proved sufficiently attractive to secure worthy of notice; this is indeed far from the truth, the the capital necessary for large-scale operation. Thus interior of many of the churches are beautiful and some of vision, nerve, capital overcame inertia and vitalized this the homes, with their enclosed patios, are well worth visit¬ almost dormant area. ing. The Alameda, with its Sunday parade of well-dressed and comely senoritas, should be seen by every foreigner, It is of great interest that the portion of the Com¬ and so one might go on describing features without num¬ stock lode near the surface still contains such a large ber that are of much interest in the city of Santiago; and tonnage of ore that will probably yield a profit when last but not least is the climate, excelling without fear of worked under modern conditions.