Figs. 1, 2, 3, and 4, Plate XXXVI., are different views of the machine for boring cylinders, invented by Mr Murray of Leeds. Fig. 1. is an elevation, and fig. 2. a plan of the machine. W fig. 1. and 2. is the spur wheel, deriving its motion from water steam, and communicating a revolving motion to the boring bar. The toothed wheel A fig. 1. moves round with the boring-bar 11 on which it is fixed ; it gives motion throngh the wheels D and E, and to the screw S, whose threads act on the two racks, which racks are fixed to the cutter-head H, and revolve with it. The velocity with which the cutter-head is impelled along the cylinder, depends upon the number of threads of the screw in a given length, and on the- proportions of the wheels A, C, I), and E to each other. By va rying the velocity of the screw, the cutter-head may be made to move in either direction, up or down the cylinder. F is a pinion, whose aids ends in a square, which may be wrought by a key, so as to bring the cutter-head out of the cylinder, or push it home by the hand when that is required.
The cylinder is fixed in its bed by screws passing through two iron rings, as represented at fig. 4.; in this way the cylinder is equally pressed in the differ ent parts of its circumference.
Fig. 8. is a transverse elevation of the collar in which the end of the bar at A, fig. I. turns; X is the gudgeon in which the spindle X, fig. 1. turns. In fig. 3. are also seen the two apertures through which the two racks pass.
By this machine also, the flanges are turned truly plane, so that the lid of the cylinder may fit on ex actly.
The patent granted in 1799 to Mr Murdoch, En gineer, Redruth, for new methods of constructing steam-engines (See Repertory of Arts, Vol. XIII.), contains some articles relative to boring. He em ploys an endless screw, turned by the moving power ; this screw works into a toothed wheel, whose axis c,arriesthe cutter-head; and this method, he says, pro duces a more smooth and steady motion than the usual mode of fixing the boring-bar immediately on the axis turned by the moving power.
Another article in Mr Murdoch's patent that re lates to boring, is his method of forming the cy linder and steam case. He casts them of one solid piece, and then bores a cylindrical interstice, by means of a boring tool, made of a hollow cylinder of iron, with steel-cutters fixed to its edge, and act ing like a trepan.
The chambers of brass pumps, whose diameter does not exceed a few inches, are fixed within iron rings, by means of screws, in the manner described above when speaking of Mr Murray's apparatus. The rings are made accurately cylindrical by turning, as is also the boring-bar. The boring-bar has four cross arms on its outer extremity, to one of which a handle is fixed, whereby a workman makes the boring-bar revolve. The cutter-head is made to advahce along the bor ing-bar by a screw.