. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . r eachof the divisions to be traced. This table hasusually 720 teeth, each one of which, conse-quently, answers to half a degree. Its axis isa steel frustum of a cone resting upon a springin a bronze socket fixed to the support T. The chief difiQculty of the operation consistsin properly centring the circle to be do this, it is first fixed upon the table withwax, and the distance from every point in thecircumference of the circle to the centre of
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . r eachof the divisions to be traced. This table hasusually 720 teeth, each one of which, conse-quently, answers to half a degree. Its axis isa steel frustum of a cone resting upon a springin a bronze socket fixed to the support T. The chief difiQculty of the operation consistsin properly centring the circle to be do this, it is first fixed upon the table withwax, and the distance from every point in thecircumference of the circle to the centre of the table carefully measured. When this distance isthe same in all points, the circle is fixed with a mixture of wax and resin, and the operation ofdividing the limb proceeded with. The operation of centring is a delicate one, but it is indis-pensable, especially when it is required to divide the limb of an instrument used for astronomicalpurposes. Improved Wood Screw and Driver.—The slotted head of the common wood screw is frequentlysplit when much force is required to seat it or to remove it, and every mechanic has been annoyed. HAND-TOOLS. 1805 by the slipping off of the screw-driver blade from the head of the screw. To provide a remedy forthese objections is the object of P. N. Jacobus, the inventor of the screw and driver shown in , 3464. The screw-head has three V-shaped notches cut equidistant in the edge, instead ofthe sirlgle-cross slot. The screw-driver, seen in perspective in Fig. 3463, has three correspond-ing jaws which by a simple arrangement automatically open and close upon the screw-head,Fig. 3464. 3463. 3464.
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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering
