These sectors for oscillating engines need not be forged in one piece, as indicated in the sketch No. 119; for the convenience of the turning and shaping processes, the guide-rod may be keyed or screwed into the stud-boss of the sector, instead of being solid with it.

When the rod is a distinct piece, it is often circular throughout its whole length, so that but little forging is needed if the metal of which it is to be made is not too large in diameter. Either steel or iron is suitable, by reason of the very small strain imparted to such rods.

The sector with its boss for containing the lower end of the guide-rod is shown in Fig. 155. Such a piece is easily drawn down from a bar whose width equals the total width of the intended sector, boss included. The ends shown by B (Fig. 119) are then thinned to their dimensions for receiving the bearing brasses, and the boss is shaped to a circular form

When a sector is thus made of one piece, the slot is drilled and shaped by a suitable machine, instead of making any slot while on the anvil. Such a sector without a rod may be made also of two straight pieces, as shown in Fig. 156. These pieces are scarfed, or a tongue-joint made at the place indicated in the Figure.

To forge a sector entirely of one piece solid with the guide-rod, it is necessary to weld the rod to the boss part of the sector, which is made either of one piece or two.

The boss, or that projecting part which is to be welded to the rod, should be midway between the two ends of the intended sector-slot; and any alteration of situation that may be needed should be done previous to welding it to the rod. To discover the proper place for the boss, the length and place of the slot is marked upon the work; a pair of compasses is then used to ascertain the middle or centre of the slot. This centre is also the centre of the intended boss or lower part of the rod ; so that if the boss-portion is not in its proper place, it can be put right. When the boss is large enough, a piece or pieces may be cut from one side to make the boss central; but if not large enough to admit cutting, it is heated to nearly welding, and driven to its proper situation by a few blows with a set-hammer

To avoid trouble with the boss, it is preferable to shape it before trimming the ends of the sector to the finished length. For this purpose one foot of the compasses is placed at the centre of the boss, or centre of intended slot, and the other foot is used to mark the half-length of the work ; the two ends are then shaped, and finally cut to an equal length.

After all the joints are welded, the work needs adjustment, to produce the required curve in the sector proper, and to place the rod at a right angle with the remainder of the work.

This adjustment is readily effected by making a few lines on a surface-table to indicate a full-dimensioned outline of one side of the sector with its rod. The sector is then placed between the lines, and any irregularity in the curve, or in the situation and position of the rod, is detected and corrected accordingly.

Templates also, are much used in the adjustment of heavy work. These templates, being made of thin sheet iron, are very portable ; also easily constructed, and applicable to either links, band excentric-rods, or sectors.

A sheet-iron template is used also in those cases in which the sector is forged, slotted, and shaped while distinct from its rod; the rod also being turned previous to welding it to the sector-boss.

To make a sector template, a sheet of thin iron is provided and flattened. A straight line is marked with a steel scriber along the length of the sheet. This line represents the centre of the guide-rod of the intended sector,- and if one sheet of iron is not of sufficient length, part of another sheet or a whole sheet is riveted to the first one. While the sheet is lying on a table or block, the two arcs that denote the extreme forged width of the sector are marked upon the iron with compasses, and to an equal distance from both sides of the centre line; one foot or leg being in some part of the centre line, while the other leg is sufficiently extended to mark the arcs desired. When the template is large, it may be necessary to put one point of the compasses in some part of the table, instead of the sheet; in these cases, the iron is fixed to the table or block with a few weights around the edges, while the centre line is continued to any desired distance along the table. Any point in this fine may then be selected as a centre from which to mark the arcs. The width or diameter of the guide-rod is also denoted by two other straight lines, one at each side of the centre fine.

When the shape of the sector ends also are marked, cutting out the template is next effected with a chisel and hand-hammer ; or if the work is too large for a hand chisel, with a rod-chisel and small sledge-hammer. Any additional corner pieces that may be required are then riveted to the template, and the shape completed by careful fifing to the lines, and flattening on the table or block.

The use of such a template or gauge to the smith, results from the extreme lightness and portability allowing it to be put upon the top of the work at any moment during the forging; also the convenience of referring to the gauge at any future time when a new sector is to be made, or an old one mended.