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Horizontal Boring Machines.-The horizontal position is the most convenient one which can be adopted for long bars which have to pass through work and be supported at the other end. The number of machines using this arrangement is therefore large, and numerous variations are introduced for special purposes. Two main differences are noticeable: in one design the position of the bar is fixed and the work has to be moved vertically and laterally to suit it; in the other the bar is adjustable, and is shifted about to accommodate the work, which is bolted in one position, the two types being used for smaller and larger work respectively. In most cases the

driven from the stepped cones B, back geared (the gears being protected with guards) through keys in splines running the length of A. Sixteen speeds are obtainable in connection with a two-speed counter. Leaving the feed arrangements of the bar for the moment, and considering the table c; this slides on a vertical face of the headstock framing by gibs, and is also clamped by a couple of bolts to a steady D, with vertical slots, and a bearing at the top to receive a bush in which the bar A is steadied. A pair of bolts E, E clamp c at the slide end. Raising or lowering is done by the screws F, F, operated by worm gear from the shaft G, slowly by a ratchet

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Fig. 184.-Horizontal Boring Machine. Front Elevation. (H. W. Ward & Co.)

work is not moved during boring, but either the bar is fed along, or a head upon it slides. Machines are constructed with a single bar, or two or more, to bore separate pieces of work, or several holes in the same casting. Double cylinders may be bored simultaneously, or the four valve chambers of a Corliss cylinder, or the guides and crankshaft bearings of an engine, the bars lying at right angles to each other in the last-named case.

An example of a machine of the first type mentioned above-having an adjustable tableis shown in Figs. 184, 185. The design is one which suggests the lathe in outline, and in fact it has been gradually evolved from that tool, the rising table, and sliding bar introducing points of difference that are necessary for the class of work. The bar A, 2 in. diameter, is

on the squared end at the right, or quickly by power from a belt pulley at the left-hand end. The screws F pass through the worm wheel nuts in bearings H, H. The first slide J moving along the table c, is operated with a screw, rotated at either end as convenient, by the square K, acting direct, or L, working bevel gears. On J there is a cross slide м, provided with tee slots, and above this may be bolted a circular table N, shown in Fig. 184 only.

Returning again to the boring bar; the feeds, of which there are eight, are derived from gears driven from the tail end of the spindle inside the headstock. A set of change-speed gears in the box o, operated by the levers P and Q, and reversed by R, give the eight speeds to the shaft s. The latter has a keyway cut along its length, and drives a sliding worm in the box T.

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Fig. 187.-DUPLEX-SPINDLE BORING MACHINE. (Wm. Muir & Co., Ltd.)

To face page 198.

The worm rotates a worm wheel which is clutched to a pinion gearing in a rack in the tail bracket, so that the feed bracket behind T travels along the ways of the tail bracket. The boring bar is moved at will by tightening a couple of set-screws, which press keys into two splines on its sides, and so force the bar to move with the bracket. A quick return may be given to the bracket by the hand-wheel U, and a slow one by v.

What is termed the "snout" boring machine, Fig. 186, Plate XIII., is a favourite type for cylinder boring, especially where one end of the

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Fig. 185.-Horizontal Boring Machine.
End Elevation.

cylinder is closed, as in many. steam and gas engines. The boring bar is carried in the head, and passes through the long boss or snout, running in a conical bearing at the end. This snout is stiff enough to support the bar rigidly, so that it may pass into deep bores. A fourstepped cone pulley at the back drives by worm gear to the spindle, and there are four power feeds of the saddle along the bed, and a rapid means of adjustment by the star handle seen in front. For certain classes of work the boring rings shown on the saddle are of service. The cutters are held in the head by a circular plate, and a couple of set-screws to each. Double-spindle machines of the type in Fig. 187, Plate XIII., are used for boring duplex cylinders, pumps, &c.

For objects of awkward shapes, and of large

dimensions, the style of machine shown in Fig. 188, Plate XIV., is employed, the illustration representing a comparatively small size. In the larger machines, Fig. 189, Plate XIV., the table and sliding ways give place to a large plain plate, provided with tee slots, enabling the work to be bolted anywhere, and the steady rest (if used) for the bar to be brought up as close as desired. In the machine illustrated in Fig. 188, the bar, provided with a range of speeds, and of feeds, is adjustable on the vertical face of the housing, the tail bearing in the steady frame being adjustable also. The table is moved by hand, or power, and its top swivels, so that holes may be bored at various angles in a piece of work without re-adjusting and bolting it down. Milling can also be done with the spindle, this class of machine often thereby finishing a piece of work outright where it would otherwise have to be sent to a separate miller or planer.

Horizontal Drilling Machines.—These are rather limited in design, the most common pattern being that of a table or base, at one end of which the drilling head is located, being adjustable vertically and laterally. The principal use of the machine is for drilling the holes in pipes and columns, which are too long to be stood on end to have their flanges drilled on a vertical spindle machine. Some rail drilling machines are also made of horizontal type, for convenience of drilling more than one hole at once. Multiple-spindle machines having two heads adjustable along a horizontal bed form a special design for pipe work, both ends being drilled simultaneously, with consequent economy of time. Apart from the above-mentioned machines there is a large class in which boring is accomplished as well as drilling; see Horizontal Boring Machines.

Hornbeam (Carpinus).-A wood used for the cogs of mortise wheels. It is of a light colour, tough and fibrous, and moderately hard. It wears well. Sp. gr. 0.76. A cubic foot weighs about 47 lb.

Horn Block.-The casting in a locomotive framing which receives the axle box.

Horn Plates.-The separate guides which are bolted to truck frames of rolling stock, and between which the axle boxes are placed. Horse Gear, Bullock Gear, Cattle Gear,

or Pony Gear.-A valuable agent where animal power only is available for operating well pumps and other machines. It comprises a long pole to which the animal is yoked, turning the shaft of a crown bevel wheel. This in turn operates a pinion on the end of a two, or three-throw crank, to which the pump rods are attached.

Fig. 190 illustrates a horse gear made by Messrs Hayward, Tyler, & Co., Ltd., for threethrow pumps. The animal is yoked to the swingle tree at the end of the pole. The amount of water that can be raised depends on

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doubled the power of a horse, working at a whimgin. The mean pressure in the cylinders of his engines was 7 lb. per sq. in. He fixed the proper piston speed at 128 x stroke÷ 33,000, and called the result the nominal horse power (N.H.P.). As pressures grew, the term fell into partial disuse, though retained for a long time as a standard for selling by, and in marine engines. But engines are now rated by the actual power which they are able to develop, as tested by the indicator, hence termed indicated horse power (I.H.P.). There is no advantage, therefore, in

giving the various antiquated rules by which the N.H.P. of various engines might be estimated.

Indicated horse power is obtained from the indicator diagram, from the total area of which the mean pressure in the cylinder is found. This, multiplied by the area of the piston in square inches, and by the speed of the piston in feet per minute, and the result divided by 33,000, gives the I.H.P. of the engine, working only under those conditions of pressure and speed. The I.H.P of a pair of compounded engines is obtained by adding together the mean pressures shown on top and bottom cards, with piston speeds, and areas, and dividing by 33,000. The French horse power, force-de-cheval, or cheval, equals 75 kilogrammetres of work done per second. The kilogrammetre = 7.233 foot pounds. It is therefore the equivalent of 542.5 foot pounds per second; of 0.99 HP., and of 736 watts. The electrical horse power is 746 watts. See p. 201. Since the unit of heat 33,000 is equal to 772 ft. lb., a HP.: = 42.75 772 heat units per minute.

Fig. 190.-Horse Gear.

the size of pump, and on the height of lift, for which tables are supplied by the firm. If two horses are used, the same quantity of water can be raised to double the height.

A pony, mule, or bullock cannot do so much work as a horse, and therefore the gear for these are made less powerful than for horses. A bullock also only walks about half as fast as a horse.

Horse Manure. Used in foundries for mixing with core sand, and loam.

Horse Power.-Proposed by Watt as the measure of power in his steam engines. He

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The horse power of a boiler is an expression for the pressure and volume of steam required to supply an engine of the same horse power. It is a question of grate area, and heating surface;

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