Engineers Shearing Tools Generally Worked By Steam 200258

The above machine which measures in total height about five feet, makes 12 or 15 strokes per minute, shears 1/2 inch iron plates, and punches 3/4 holes in iron 1/2 inch thick. A larger machine makes 10 or 12 strokes per minute, shears 3/4 inch plate, and punches 1 1/4 inch holes in iron 3/4 inch thick; and a still heavier machine working at 8 or 10 strokes in the minute, shears 1 inch plates, and punches 2 inch holes in iron 1 inch thick. Some of these are provided with railways by which the work is carried to the shears or punches as will be described; and Mr. Roberts' bar-cutting machine, having only shearing cutters at the bottom, and the execntric at the top of the slide, is used for cutting bars not exceeding 6 3/8 inches wide by 1 5/8 thick, or bars 2 or 2 1/2 square, but he thinks these dimensions of the works performed might if required be greatly exceeded in heavier machines.

A patent has been recently granted to Mr. G. B. Thorney-croft, for a shearing machine for cutting wide plates of sheet iron. This machine which is used in the manufacture of wrought iron, has two wide cutters of steel fixed to the edges of thick plates of cast iron; the lower cutter is at rest and quite horizontal, the upper cutter bar is fitted in grooves at the end of the frame, so as to be carried up and down vertically, by a shaft or spindle immediately above the cutter and parallel with it, this shaft has an execntric at each end, and one in the center, and three connecting links, which attach the cutter frame to the excentrics, and give it a small reciprocating motion. The upper cutter is a little oblique so as to begin to act at the one end, and in removing the strips curls them but very little.*

Nasmyth, Gaskell and Co.'s vice for cutting wide pieces of boiler plate, is based on the mode of cutting thin slips of sheet metal over the chaps of the ordinary tail vice as described on page 918-9. The jaws of the machine are about six feet long, faced with steel, and powerfully closed by two perpendicular screws and nuts, one at each end, which also secure the machine to the ground.

The plate of iron is therefore fixed horizontally and with the line of division level with the jaws. A strong rod chisel struck with sledge hammers, is applied successively along the angle formed between the work and the vice, and after the iron has been indented the whole length, the blows of the sledges directed on the overhanging piece of iron complete the separation.†

Fig. 983, represents the plan, and fig. 934, the partial vertical section, of a "hydraulic machine for cutting off copper bolts,"

* Thorneycroft's Patent, sealed Slat January, 1843, La described in the Repertory of Patent Inventions, Vol. ii., Enlarged Series, page 129.

† Nasmyth, Gaskell and Co.'s cutting vice is figured in plate 49 of Buchanan's Mill Work, edited by Sir Q. Rennie, F.R.S., 1841.

devised by Mr. A. M. Renton, and constructed for the Government Dock Yards, by Messrs. Charles Robinson & Son. This machine is actuated by the hydro-mechanical principle discovered by the celebrated predecessor of the firm, Mr. Timothy Bramah.

The circle in fig. 933, represents the cylinder of a hydrostatic press, which is flattened to the width of the rectangular bar that is fixed alongside the cylinder, the two being enveloped in the external casting which is shaded in the section fig. 934, and resembles a stunted pillar three or four feet high. The whole of the parts are traversed by nine sets of holes suitable to bars from 3/8 to 2 1/2 inches diameter, the holes where they meet on the lines b b, are furnished with annular steel cutters, and are enlarged outwards each way to admit the work more easily.

The rod r r, to be sheared, is introduced whilst the holes are directly opposite or continuous, and the men then pump in the injection water through the pipe w, it acts upon the annulus or shoulder intermediate between the two diameters of the cylinder, causes the descent of the latter with a pressure of about 100 tons and forces the bar asunder very quietly, and from the annular form of the cutters without bruising it. When the bar has been cut off, the injection water is allowed to flow out from beneath the cylinder, and the latter is raised by a loaded lever beneath the floor ready for the next stroke. The machine is far more economical in its action, than the old mode of cutting off the copper bolts, with a frame saw used by hand, and the storekeeper in charge of the bolts, can if needful perform the entire operation unassistedly, although usually four men work the pair of one inch injection pumps, by a double-ended lever as in a fire engine.

Engineers Shearing Tools Generally Worked By Steam 200259

In concluding this chapter it is proposed to speak of the rotary shears for metal, which have continuous action like rollers and are pretty generally used. In the best form of the instrument, two spindles connected together by toothed wheels of equal size, have each two thin disks of different diameters, which are opposed to each other, that is, a large and a small in the same plane, as in the diagram fig. 935, the larger disks overlap each other and travel in lateral contact, and therefore act just like shears, and the two disks in each plane meet, or rather nearly meet, so as just to grasp between them, after the manner of flatting rollers, the two parts of the strip of metal which have hi severed, and by carrying these forward they continually lead the yet undivided part of the metal to the edges of the larger disks, which in this manner quickly separate the entire strip of metal into two parts.

The machine requires that the spindle carrying the disks should have an adjustment for lateral distance, as in flatting rollers, to adapt their degree of separation to the thickness of the metal to be sheared. One of the spindles should also have an endlong adjustment to bring the disks into exact lateral contact, and the machine requires in addition a fence or guide, fixed alongside the revolving shears to determine the width of the strips cut off. Sometimes the two smaller disks are omitted, and the larger alone used, as in fig. 936, the circular shears are then somewhat less exact in their action, but perform nevertheless sufficiently well for most purposes.

Circular or rotary shears, are very useful for shearing plates not exceeding one-eighth of an inch thick, and one of the advantages which the rotary possess over the common shears, is the facility with which curved lines may be followed, on account of the small portion of the disks that are in contact, whereas the length of rectilinear shear blades prevent their ready application to curves. Of course the speed at which the machines may be driven depends on the nature of the work, and if the cuts are straight and the plates light, the velocity of the shears may be considerable.

As remarked on page 188 of the first volume, the circular shears, or splitting rolls used in the works where wrought iron is manufactured, are composed of steel disks of equal thickness, but of two diameters, arranged alternately upon two spindles as in fig. 937, so as at one action to split thin plates of iron of about 6 inches in width, into very narrow pieces known as nail rods, and into strips from half to one inch wide designated as bundle or split iron. Of course different pairs of rolls are required for every different width of the strips thus manufactured.