The ordinary tail-vices, or standing-vices for heavy engineering and large works, sometimes exceed 100 lbs. in weight; but the average weight of tail-vices, for artizans in genera], is from 40 to 60 lbs., and of those for amateurs, from 25 to 35 lbs.

The bench for the vice usually extends throughout the length of the engineer's shop, or vice-loft, and is secured against the windows. The tail-vice is strongly fixed to the bench at the required height, and the tail that extends downwards is fixed in a cleet nailed to the floor, or against one of the legs of the bench, which latter mode is desirable, as the vice is then in better condition to resist the blows of the chisel and hammer, which give rise to much more violence than the act of filing.

Amateurs sometimes employ portable vice-benches, having nests of drawers for containing the files and other tools; or the vice is attached to the right-hand side of the turning-lathe; less frequently the tail-vice is attached to the planing-bench, but it is then requisite it should admit of ready attachment and detachment, to leave the planing-bench at liberty for its ordinary application.

Fig. 842 represents a very convenient mode of mounting the tail-vice upon a tripod stand of cast-iron, which indeed is in many cases preferable to the wooden benches; as although small, it is sufficiently heavy to ensure firmness, especially as from having only three points of support, all are sure to touch the ground. The tripod readily admits of being shifted about to suit the light, and also of temporary change of height, by liftingpieces added to the feet, when the work is required to be nearer to the eye of the operator. The tripod pedestal serves additionally for the occasional support of a small anvil (when not required for forging), and also for a paring knife, fig. 8, page 26, Vol. I.), when an appropriate wooden cutting-block is added to the tripod.

The table-vice mostly used by watch-makers and similar artizans, resembles that shown in figs. 843 and 844. It is attached to the table by a clamp and screw, which are armed with teeth to give a secure hold; but it is usual to glue a small piece of wood on the table to receive the teeth, and also to prevent the lodgment of small pieces of the work at that part, and the work-table has also a ledge around it, to prevent the work or tools from rolling off. It will be also perceived, that the clamp is surmounted by a small square projection a, used as a stake or anvil; and that the jaws of the vice have center holes on one or both sides for the employment of small center drills, that are too delicate for the breast-plate, after the mode described in page 553 of the present volume.

It is in all cases desirable that the jaws of vices should be exactly parallel, both with the edge of the bench and with the ground, in order that the position of the work may be instinctively known; but the tail-vice and bench-vice are liable to various objections that arise from their opening on a center, or as a hinge; for although the jaws are almost parallel when closed, or then nip in preference at the upper edge, when opened widely, the radial position of the jaws causes the lower edges alone to grasp the work, and as in addition, the front jaw moves in a circular arc, a wide object, on being fixed, is necessarily thrown out of the horizontal into an inclined position; each of which imperfect conditions is shown in fig. 844.

Fig. 842.

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Table-Vice For Small Works

Figs. 843.

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844.

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The inclination of the two limbs of the vice, likewise depreciates the contact of the screw and nut; this is sometimes remedied by a modification of the ball and socket already described. A more simple mode is the employment of a washer of the form represented at to, fig. 842, which is placed beneath the screw; the fork embraces the lower extremity of the curved jaw of the vice, and the washer being thickest in the center, rolls, so that the flat side always touches the entire surface of the shoulder of the screw, and the central and bulged part of the washer touches the limb of the vice, and causes the pressure to be nearly central upon the screw, instead of, as in fig. 844, against the upper edge of the collar of the screw, which is then liable to be bent and strained. The box or internal screw, b, fig. 842 in which the screw-pin works, has also a power of adjustment or hinge-like rotation, which ensures, here likewise, centrality of pressure. This mode is extremely simple, and worthy of general adoption.

The inconveniences common to vices opening radially on a joint pin, are completely removed in those opening on straight slides; these arc called parallel vices, because the surfaces of their jaws or chaps, and also the bearings of their screws and nuts, always retain their parallelism; consequently whether the work be wide or narrow, it is always firmly grasped by the chaps, provided the work be itself parallel. One of these vices is represented in fig. 845. The front jaw is forged in continuation of the body of the vice, the whole being of a rectangular form, and receiving at its upper parts the extremities of the pinching screw, which has a semi-cylindrical cover to protect it from the file-dust. The back or sliding jaw of the parallel vice fits accurately upon the upper surface of the principal bar at a, and also upon a square bar b, placed above it.

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Parallel vices are sometimes attached to the table or bench, by clamps that only allow them one fixed position, namely, with the jaws parallel with the bench, as in the bench-vice, fig. 843; but more generally the clamp of a parallel vice, c c c, fig. 845, has a vertical socket or hole, and the principal piece of the vice terminates in a round stem that fits the socket, and has a nut n, by which means any horizontal inclination may be given to the jaws; they are represented inclined, or they may even be placed at right angles to the bench.

Some parallel vices are attached to the table by ball and socket joints, as shown detached in fig. 846; and various similar schemes have been proposed. The screw-clamp is attached to the table by a thumb-screw a, and the clamp terminates in a portion of a sphere; the lower part of the vice has two shallow spherical cups adapted to the ball, so that by turning the thumbscrew b, the ball is grasped between the two cups. It is true this kind of parallel vice may be inclined both horizontally and vertically, and therefore offers much choice of position; but it is too unstable in any to serve for more than very light works, which require but a small application of force.

The jaws of vices are faced with hardened steel and cut like files, so as to hold securely: but works that are nearly finished would be injured by the indentation of the teeth, and are therefore protected by various kinds of shields or vice-clamp*, as they are generally called; several of these are shown in figs. 847 to 6

Vice-clamps, such as fig. 847, are often made of two detached pieces of stout sheet-iron, brass, or copper, of the length of the chaps of the vice, and nearly as wide. The two pieces are pinched between the jaws, and then bent closely around the shoulders of the vice to mould them to the required form, and make them easily retain their positions when the work is removed from between them.

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Sometimes sheet lead an eighth of an inch thick is used; but such clamps answer better when cast in the rectangular form, as in a, fig. 848, and then bent as at b; the lead should be hardened with a little antimony, to resemble a very soft type metal (Vol. I., page 277), and, previously to bending the clamps, they should be heated to about 300° to 400° Fahr., to avoid fracture. This alloy, although harder than lead, is still sufficiently soft to adapt itself to irregularities in the objects held, and the clamps being thick, last longer, and more readily admit of being restored to form by the hammer or rasp, than those made of sheet lead.