MECHANICS AND USEFUL ARTS. 61 



tion of those now in use being of the worst conceivable form to 

 effect the object they are designed for. 



The speaker referred to the common form of drill, and, at the 

 same time, exhibited a sheet of drawings on which a number of 

 different forms of drills were marked. Some of them depend for 

 cutting action on, to use a homely phrase, "strength and stu- 

 pidness," no attempt whatever being made to form a proper 

 cutting angle. Others are more advanced in form, and have a 

 proper cutting angle provided ; sometimes a small portion of the 

 bottom end, he said, is turned, and forms, in this condition, a 

 very excellent working tool indeed. A twist drill was next 

 spoken of, which was the real object of bringing this paper under 

 the notice of the society. 



These. drills have been known for a considerable length of 

 time, but have not been much used in this country until recent 

 years, Americans having been ahead in their use, and in manu- 

 facturing them as well. Strange as it may appear, it is still true, 

 that all the drills of this class were, until within a recent period, 

 imported from the United States. 



Due consideration being given to the principles already ex- 

 plained, the advantages arising from the use of twist drills will 

 be apparent at a glance : first, they serve as a common drill, to 

 bore a hole ; second, they serve as a guide, while boring, to keep the 

 hole true ; and, third, they are so formed as to provide the proper 

 cutting angle throughout their whole working length ; fourth, they 

 are tempered throughout their entire working length ; fifth, they 

 are ground up true to standard sizes, thus obviating any neces- 

 sity for dressing. This last advantage will doubtless be highly 

 appreciated by all who have had practical experience of the con- 

 tinual trouble and loss incidental to the wearing out of size of 

 common drills. 



The speaker then said, until the recent improvements which I 

 am about to lay before you were perfected, twist drills were 

 formed entirely by the clumsy method of cutting them out of a 

 solid round bar, by means of milling tools, then turning, temper- 

 ing, and straightening; it is but justice, however, to the parties 

 who have been hitherto engaged in the manufacture, to say that 

 their arrangements and machines for that purpose were admira- 

 ble of their kind. 



The method now pursued successfully in this country differs 

 entirely from that just mentioned. First, the bar of steel which 

 is destined to form the drill is rolled into a special shape ; it is 

 then cut into lengths and again rolled in cam rolls, which form a 

 straight groove, after which the shank is formed by cresses. 

 Next the blank, as it is now called, is passed to the twisting- 

 machine, which consists essentially of a hollow spindle having a 

 perforated nut in the end to receive the blank. This spindle, 

 when the machine is started, has a motion of rotation on its own 

 axis, and also a motion of translation in the direction of its axis, 

 being thus adapted to twist the blank, then held firmly at the 

 outer end by vise clamps. Other clamps, worked by suitable 

 gearing, close on the blank as the central- spindles clear them ; 

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