724 



BORING MACHINE. 



u. 



cltine 



Plate 

 I.XIV. 



rig. 5. 



figs. 2, 3, 

 4. 



is oul)' used to smooth, and make true, the internal 

 surface of the cylinder, which is cast hollow. 



The accuracy of cylinders for pumps, steam en- 

 gines, blowing engines, &c. is an object of so much 

 importance in the construction of machinery, that 

 many very expensive engines have been made for the 

 purpose. The old and common method is to have 

 an horizontal axis turned slowly round by the mill, 

 at the end of which a borer is fixed, and the cylinder 

 is fastened down upon a carriage, sliding in a direc- 

 tion parallel to its axis, and drawn forwards to the 

 borer by the descent of a weight. The objection to 

 tiiis method is, that any deviation from a rectilineal 

 motion in the carriage will be transferred to the cy- 

 linder, and cause it to be crooked ; and that the 

 weight of the borer and its axis acting on the lower 

 side only of the cylinder, causes it to cut away more 

 at that part, and render the metal of the cylinder of 

 unequal thickness. This evil, however, was in some 

 measure obviated by a contrivance of Mr John 

 Smeaton, which was a steel-yard mounted upon a 

 moveable wheel carriage, running within the cylin- 

 der. By suspending the weight of the cutter and 

 boring bar from it, the machine was much improved, 

 though still very imperfect. 



A boring machine, for metal cylinders, which is 

 not liable to any of these sources of error, is construc- 

 ted in the manner shewn in Plate LXIV. Figure 5. 

 is a perspective view of the machine in the action of 

 boring out a cylinder for a steam engine ; the other 

 Figures explain the construction of its parts, and are 

 drawn to a scale. In Fig. 5. AA denote two oak 

 ground sills, which are firmly bolted down parallel 

 to each other upon sleepers let into the ground. At 

 each end of these a vertical iron frame, BB, is erect- 

 ed, to support the gudgeons at the end of a long cy- 

 lindrical axis DD, which is turned round by the mill. 

 The cylinder LL, which is to be bored, is fixed un- 

 moveably over this bar, and exactly concentric with 

 it. A piece of cast iron, KK, LL, (Figs. 2, 3, and 

 4.) called a cutter head, slides upon the axis, and has 

 fixed into it the knives or steehngs, _f, J", J", which 

 perform the boring. This cutter head is moved along 

 the bar by machinery, to be hereafter described ; by 

 means of which it is drawn or forced through the 

 cylinder, at the same time that it turns 1'ound with the 

 i'.xis D. The steel cutters will necessarily cut away 

 and remove any protuberant metal which projects 

 within the cylinder, or the circle which they describe 

 by their motion, but cannot possibly take any more. 



The cylinder is held down upon an adjustable fra- 

 tning, which is readily adapted to receive a cylinder 

 of any size within certain limits. Pieces of iron EE 

 are bolted down to t'le ground sills^ having grooves 

 through them to receive bolts, which fasten down two 

 horizontal pieces of cast iron FF, at right angles to 

 them. These horizontal pieces support four move- 

 able upright standards GG, which include the dia- 

 meter of the cylinder LL, which is supported upon 

 blocks bb below, and held fast by iron bands art, 

 drawn down by screws in the top of the standards 

 GG. The cylinder is adjusted to be concentric with 

 the axis DD, and held firmly in its place by means of 

 wedges driven under the blocks and the standards. 



To explain the mechanism by which the cutters 



are advanced, we must refer to Figs. 2, 3, and 4; by Boring 

 the inspection of which, it will be seen that the axis DD Mac h>nr 

 is, in fact, a tube of cast iron hollow throughouti It is 1 v ""' 

 divided by a longitudinal aperture cc, Fig. 4, on each l.xiv* 

 side. At the ends it is left a complete tube, to keep rig. 4. 

 the two halves together. The cutter head KK, LL, 

 consists of two parts, of a tube KK fitted upon the 

 axis D with the greatest accuracy, and of a cast iron 

 ring LL fixed upon KKbyfour wedges. On its cir- 

 cumference are eight notches, to receive the cutters 

 or steelings f,f, which are held in, and adjusted by, 

 wedges. The slider K is kept from slipping round 

 with the axis, by means of two short iron bars ce, 

 which are put through the axis, and received into 

 notches cut in the ends of the sliders KK. These 

 bars have holes in the middle of them, to permit a 

 bolt at the end of the toothed rack L to pass through. 

 A key is put through the end of the bolt, which, 

 at the same time, prevents the rack being drawn 

 back, and holds the cross bars ee in their places. The 

 rack is moved by the teeth of a pinion N, and is kept 

 to its place by the roller O : the axis of the pinion 

 and roller being supported in a framing attached, to 

 the standard BB, as shewn in the perspective view of 

 the machine in Fig. 5. The pinion is turned round 

 by a lever put upon the square end of the axis, and 

 loaded with the weight P, that it may have a constant 

 tendency to draw the cutter through the cylinder. 

 This lever is capable of being put on the square end 

 of the axis either way, so as to force the rack back 

 into the cylinder if necessary. 



In some boring machines, another contrivance, su- 

 perior perhaps to what we have now described, is 

 employed to draw the cutter through the cylinder. 

 It consists of four small wheels, one of which is fix- 

 ed at the right hand extremity D, of the bar DD, 

 Fig. 4. Another pinion is fastened on the extremity 

 of an axis, analagous to the rack M, having at its 

 other extremity a small screw, which works in a fe- 

 male 6crew, fixed to the cutter KK at e, (Fig. 2.) 

 Below the second pinion is another containing the 

 same number of teeth, and fixed on a horizontal axis 

 parallel to DD. At the other end of this axis is a 

 fourth pinion, which is driven by the first pinion at 

 the end of the hollow axis DD. The first pinion 

 has 26 teeth, the fourth 30, and the second and third 

 may have any number, provided they are equal. As 

 the axis DD revolves, the first pinion fixed on its ex- 

 tremity drives the fourth, which, by means of the 

 third fixed on the 6ame axis with it, gives motion to 

 the second. The second pinion being fixed to an 

 axis within DD, unscrews the screw at its other ex- 

 tremity, and of course makes the cutter advance along 

 the cylinder. This screw has eight threads in an 

 inch, and sixty turns of the axis arc required to cut 

 one inch. 



To introduce a cylinder into its place in the ma- 

 chine, it is necessary to remove the upper braces 11 

 of the bearings, upon the standards BB ; and by sup- 

 porting the axis upon blocks placed under the mid- 

 dle of it, the standard, with the pinion N and roller 

 frame, is removed, by taking up the nuts which fas- 

 ten it down upon the ground sills AA, the rack M 

 being supposed previously withdrawn. A cutter 

 block L, of the proper size to bore out the intended 



