Hand-vices are not, however, in all cases employed; but small wires and other pieces are also held in a species of pliers, fig. 861, called pin-tongs or sliding-tongs, which are closed by a ferule that is drawn down the stem. Fig. 862 shows another variety of this kind, that has no joint, but springs open by elasticity alone when the ring r is drawn back.
The small pin-vice, fig. 858, is used by watchmakers in filing up small pins and other cylindrical objects; the jaws are not united by a joint, but are formed in one piece with the stem of the vice, the end that constitutes the jaws being divided or forked; the screw and stem are each perforated throughout, that the ends of long wires may be filed; and the stem is octangular that the pin-vice may be readily twisted to and fro between the fingers and thumb of the left hand, whilst the file is reciprocated by the right hand, and in this manner a considerable approach to the cylindrical form is obtained.
Independently of the rapid movement of the hand-vice to and fro on its axis, simultaneously with the strokes of the file, the two hands being moved together, the hand-vice is thrown progressively forward with the fore-finger about a quarter of a turn at nearly every alternation, so as to bring all parts of the work alike under the operation of the file. But as it is in this case important that the work should be pinched exactly central in the vice, or so that the axis of the work may pass through the axis or central line of the vice, a central angular groove is frequently made in each jaw of the hand-vice, to give the work, without trial, a nearly axial position. This is more usual in the narrow vices, fig. 859, known as dog-nose or pig-nose hand-vices, than in those with wide or cross chaps, 858 and 860.
Many circular works that were formerly thus filed, are now, from motives of expedition and accuracy, more commonly exe-cuted in the turning-lathe, since the great extension in the use of this machine, which has become nearly as general as the vice or the file itself; but frequent occasions still remain in which the hand-vice and file are thus employed, and it is curious to see how those accustomed to the rotation of the different kinds of hand-vice with the wrist, will in this manner reduce a square or irregular piece to the circular section.
In the pin-tongs, fig. 862, besides the facility of turning the instrument round with the fingers, from the reverse end having a center and pulley, the same spring tongs serve conveniently as forceps for holding small drills to be worked with the drill-bow, and also for other purposes in watch-work.
Numerous flat works are too large, thin, and irregular in their superficies to admit of being fixed in the various kinds of bench and table-vices that have been described, and if so fixed, there would be risk of bending such thin pieces by the pressure of the vice applied against the edges of the work, consequently, different methods are employed in fixing them.
The largest flat works are simply laid on the naked surface of the work-bench, and temporarily held by half a dozen or more pins or nails driven into the bench. The pins should be as close to the margin as possible, and yet below the surface of the work, so as not to interfere with the free application of the file; it is frequently necessary to lift the work out of its temporary bed for its examination with measuring instruments, and advantage is taken of these opportunities for sweeping away with a small brush (like a nail-brush for the dressing-table,) any loose filings that may have got beneath the work, and prevent it from lying flat.
For thin flat works of smaller size, the filing-board, fig. 868, is a convenient appendage; it measures six or eight inches square, and has a stout rib on the under side, by which it is fixed in the vice. Such thin works are required to be frequently corrected with the hammer, and also to be turned over, in order that their opposite sides may be alternately filed, so as to follow and compensate for, the continual changes they undergo in the act of being filed. In some instances the work is held down with one or more screw clamps or hand-vices as represented; this is needful when pins would bruise the margins of nearly-finished works, and a card or a few thicknesses of paper are then interposed to protect the object from the teeth of the vice.
In filing thin flat works, such as the thin handles or scales of penknives and razors, and the thin steel plates used in pocket knives, the Sheffield cutlers generally resort to the contrivance represented in fig. 864, and known as a flatting-vice. A hand-vice is fixed, in the ordinary tail-vice or table-vice, by the one jaw with the screw uppermost, so that the jaws of the hand-vice are horizontal. The thin scale to be filed is then placed on a flat piece of metal not less than a quarter of an inch thick, and the two are pinched together by the one corner, so that all the remaining surface may be free to the action of the files, and the work is readily shifted about to allow all parts to be successively operated upon. The facility of changing the position is particularly useful in working on pieces of tortoiseshell, buckhorn, and other materials of irregular form and thickness, to which the filing boards with pins or clamps would less conveniently apply.
As before observed, the one face of the small filing-block f, fig. 858, is also used for very small thin works, and which arc prevented slipping from the file by the wooden ledge, or by pins driven in. In many omstamces, also, thin works are held upon a piece of cork, such as the bung for a large cask, beneath which is glued a square piece of wood, that the cork may be held in the vice without being compressed. The elasticity of the cork allows the work to become somewhat embedded by the pressure of the file, between which and the surface-friction, it is sufficiently secured far the purpose without pins.