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Indiana University Studies 



wedges are driven between steel plates called ' 'feathers". If 

 each wedge is driven in turn the rock will be split very evenly. 

 This method is also used to split up large blocks in the quarry, 

 preparatory to removal with the derricks. Drilling and blasting 

 can be carried on only where there is a covering of Mitchell 

 limestone to be stripped off and a soft layer above the building 

 stone to protect it from the jar which would tend to shatter it. 

 In one of the larger quarries where the stripping is very thick, 

 churn drills are used to make the holes for the blasts and steam 

 shovels are used to remove the waste stone. 



The most common type of drill is the simple steam drill in 

 which the drill bit is fastened to the piston of the drill, and the 

 whole machine is held in position by means of a tripod. Many 

 modifications of this form of drill are in use, and all form.s have 

 their advocates. It has been the general idea for a great many 

 years that electric drilling could not be made a success, but in 

 the last few years many successful electric drills have been put 

 on the market. The Engiiieering Magazine (December, 1911) 

 sa3^s : 



Where holes are to be drilled for blasting or plugging, reciprocating drills 

 are used exclusively. Generally these drills consist of a piston to which the 

 drill is fastened directly and rigidly, a valve for distributing the steam to 

 the ends of the piston, the valve mechanism, and a means of rotating the 

 drill to insure a round hole. Most of these types will operate on either 

 compressed air or steam. 



The uses to which rock drills are put, the class of operators who handle 

 them, and the location of the work, all demand a machine with as few moving 

 parts as possible, one rugged in design and construction, simple in operation, 

 and foolproof in adjustment, and it is such a type that represents the best 

 rock drill of today. The Sullivan tappet valve drill is a good drill for low 

 pressures and soft rock with mud seams present, such as most open excava- 

 tion work. The Ingersoll Rand butterfly valve drill is another effective 

 drill for this kind of work. 



The Little Giant drill built by the Ingersoll-Rand Company uses a 

 plain slide valve to distribute the air to the piston. In this drill the valve 

 is thrown by a rocker one end or the other ot* which is always in contact with 

 the piston and is moved on its pin by the curved surfaces of the piston. 

 This rocker in turn moves the slide valve which distributes the air. This 

 drill is also furnished with a balanced valve which is of advantage with high 

 pressure. Another type put out by the Sullivan Company is their differ- 

 ential valve drill. In this drill the valve is thrown by air. The three spools 

 on the valve differ in area, the central one being of larger diameter than those 

 on the ends. The air and exhaust parts are so situated and proportioned 

 that the valve is held to its seat under the total line pressure from one side 

 only, until the proper stroke of the piston is secured. This enables the opera- 

 tor to adapt the length of the stroke and the force of the blow at will. In 



