The two general classes of vices are taper ones and those named parallel. A taper vice opens by one jaw or leg being swung on a pivot-bolt at the lower part of the instrument; consequently, the space between the two jaws is taper, and therefore not so efficient for gripping a parallel piece of work as if the space were parallel. The space is always parallel between the jaws of a parallel vice, because one jaw is connected with a slide which slides along a parallel groove in the bed of the instrument, this bed being that which is bolted to the vice-bench. Fig. 471 denotes a parallel vice having a leg or pedestal somewhat like the leg of a taper vice; this leg is attached to the front jaw of the vice and also to its bed, and while the vice is in use, the leg, front jaw, and bed remain stationary, while the back jaw is moved backwards or forwards to grip pieces of work of various thicknesses ; this movement is therefore contrary to that of a taper vice, of which the back jaw remains stationary. To the back jaw is attached the slide which slides in the bed, and to the slide is attached the cylindrical box which contains the screw-nut belonging to the vice-screw. The box is large enough to contain a strong nut, about three inches in length, which is tightly fixed in the box. In the back jaw is a hole to admit the vice-screw, and this hole is of sufficient diameter to also admit a thin tube that covers the front end of the screw, by which it is protected from injury through filings, chips, and other substances falling upon it; the screw is therefore not seen, being hidden by the tube, and this tube is kept in its place by a small ledge which acts as a key. When it is necessary to oil the screw, the tube is pulled forwards a short distance to release the key, and then half rotated to place upwards that side which was underneath; when this is done, an oil-channel is seen ; the oil is next put in, and the screw rotated, after which the oil-channel is again put underneath to prevent anything falling into it. If it is desirable to keep the oil-hole upwards, a plug or lid may be attached. A parallel vice of this sort is efficient for chipping, through having a leg which reaches the floor, and through being heavy enough to resist the hammering.

The taper vice, denoted by Fig. 470, is also of a strong character, to render it suitable for chipping small work. The two arms are as long as convenient, to cause the space between to be nearly parallel; and the back arm or leg is tightly fitted in a gap which is formed in the edge of the bench, whether the bench is of iron or of wood.

Both parallel vices and taper ones are often used with vice-clamps; these are protectors which are placed between the gripping surfaces of the jaws and the work which is gripped. Vice-clamps are made in pairs, and a pair consists of two plates of metal that are made to fit the upper surfaces of the vice-jaws. For gripping rough iron and steel, the clamps should be made of soft sheet or plate iron, or of copper; for gripping brass, gun-metal, and polished iron and steel, the clamps are made of lead, tin, and also of plate iron to which are riveted a couple of thick strips of leather, to be in immediate contact with the work to be gripped.