The gaps here treated are those belonging to levers, joint-rods, eccentric-rods, connecting-rods, and other rods and bars in general. Some of these are forged with the gaps roughly formed, but great numbers are forged without any gap and are made with solid lumps at the ends, which are to have gaps formed therein while cold by means of machine processes of various classes.

The entire number of the processes for shaping gaps while cold may be distinguished into two sorts, which are drilling and slotting. Those rods, levers, and bars which are forged without gaps are principally shaped with drilling, through the comparative large amount of metal to be cut out. Articles in which the gaps are partly formed at the time of forging have them completed principally with slotting, little or no drilling being done, because but little metal is to be removed, and also because gaps cannot be drilled without additional pieces being fixed therein.

The lining of a solid fork-lump in which a gap is to be formed is denoted by Figs. 805 and 811. The same lining suits a great variety of rods, bars, and levers, small and large, whether they are to be shaped by hand-shaping or by machine-shaping. When the end is properly lined the article is taken to a drilling-machine to have a hole made at the bottom of the intended gap, and also, in some cases, two or three additional holes made along the gap. If a number of holes are drilled, the superfluous metal which remains between the holes is easily removed afterwards either with a shaping-machine or a slotting-machine. Slotting-tools may be used also to cut out the entire gap-piece, if only one hole has been drilled, if the article in progress is small. For large rods and bars a circular saw should be used, with which two slits are cut from the extremities of the rods to the drilled holes, only one hole being made into each gap-piece when sawing is to be done. This is a quick and easy process for the forming of gaps in large numbers, nearly all of the superfluous gap-piece being removed in one lump, instead of in the condition of shavings.

Solid gap-ends are drilled while bolted against an el-chuck, in the situation shown by the small lever in Fig. 863. In this Figure an el-chuck is seen bolted to the circular table of the drilling-machine, and to that face of the chuck which is at right-angles to the table, the article to be drilled is bolted. Either one or both the bosses may be in contact with the chuck's face, according to the comparative length of the lever for the table and chuck. By the boss-faces being thus parallel with the chuck, the operation of drilling will form a hole whose length is parallel with the boss-faces, as required, because the downward vertical movement of the drill while cutting, and the face of the chuck, are parallel with each other. Therefore if the boss-faces of the object are truly turned, and the joint-pin holes also truly bored, previous to drilling the gap, the boss-face must be put parallel with the chuck-face, in order to make the drilled hole for the gap parallel with the boss-faces, and, consequently, right-angular to the length of the joint-pin holes, which is necessary.

Levers, rods, and bars, of all sizes are drilled while bolted to el-chucks; but the modes of fixing differ a little from each other through the different shapes and sizes of the articles to be drilled. The solid gap-portions are often drilled previous to boring and turning the bosses, so that it is not always needful to put the boss-faces into parellelism with the el-chuck's face; in

2o2 many cases it is preferable to put the broad side of the flat mid-part or arm parallel with the chuck; and if the broad side is not close to the chuck-face the space is occupied by a parallel packing-piece or pieces. If the rod or bar is thus fixed, the arm is adjusted to parallelism with the chuck, and the boss is prevented from touching any part of the chuck by reason of the packing; the boss-face is therefore not parallel with the chuck-face, unless they happen to be parallel with the arm's broad side, which side is specially intended to be parallel.

Any lever or bar that has plenty of superfluous metal in the boss, and little or none in the broad sides of the arm, requires placing to the chuck with the arm in contact or against parallel pieces in order to cause the hole or holes to be drilled parallel with the broad side, and not necessarily parallel with the boss-faces. These faces having plenty of metal can be reduced after the drilling of the gap is finished, and can then be made parallel, both to the drilled gap and the mid-part or arm's broad side. But if the boss has the least amount of metal to be cut off, the object is fixed with regard to the boss instead of the arm.

A lever which has both its bosses truly faced, when to be drilled, is fixed with one or both of its bosses in contact with the chuck. When both bosses are of the same length the two faces are put close to the chuck; but when one boss is shorter than the other, a parallel ring, or parallel blocks are put between the face of the chuck and the face of the boss which is the shorter. During the fixing of such a lever it is therefore necessary to first tightly bolt the longest boss to the chuck in order to see exactly what thickness of packing is required to occupy the space between the face of the short boss and the chuck's face. By tightly screwing the fixing bolts which are holding the longer boss, the shorter one is forced into parellelism with the chuck, and also forced to the proper distance from it. Consequently the exact thickness of packing necessary is now shown by the space referred to.

The direction in which a gap extends into a rod or bar, must be parallel with the length of the rod or bar; for which, an adjustment is required previous to drilling, if the gap to be made is of comparative great length, and several holes are to be drilled in line with each other. This adjustment consists in placing the bottom edge of the chuck's face parallel with the traversing movement of the slide belonging to the machine-table. If the chuck is thus placed with the object properly bolted thereon, the object can be easily moved in the exact direction required during the drilling, in order to cause the holes to be made in line with the length of the piece as required. After the rod and chuck are at first correctly fastened and adjusted, and one hole bored, it is only necessary to advance the table and chuck a short distance by rotating the traverse screw in order to place the gap-end exactly into the required situation for another hole to be made. This hole being formed, the table is again advanced as before to make another hole, this gradual shifting being continued till all are made.

A drilling-machine which is not provided with slide-rest movements, which is the condition of the one shown by Fig. 863, requires the el-chuck to be shifted after each hole is made, instead of shifting the table and chuck at one time with a sliding apparatus. Every time a new hole is to be drilled with such a machine, the gap-end must be re-adjusted to place it into the required position; and to facilitate the adjustments after each shifting, the table should be provided with parallel straight lines. One of these lines is selected to which the bottom-edge of the chuck's face may be put parallel; and if it is thus situated, the line constitutes a sort of standard to which the bottom-edge will be again adjusted after being shifted. After one hole is drilled in the gap-end, the bolts which hold the chuck to the table are loosened, and the chuck is slid along the table in a direction which is parallel with the gauge-line ; and when moved a proper distance for the next hole, it is again fastened by tightening the bolts, and the hole is next made. A drilling-table which is devoid of lines, or which may have lines too far from each other, may be specially marked for the occasion with a scriber. This marking is done after the el-chuck is first properly fixed for drilling one hole, at which time a line is scribed upon the table parallel to, and very near to, the bottom-edge of the chuck's face.