The cutting of a key-way into a wheel-boss or into a lever-boss may be done with a driller, with a shaper, with a planer, or with a lathe. If to be done with a driller, the boss is placed upon the drilling-table with the faces parallel to the table, and therefore with the length of the intended groove at right angles, or, which is the same thing, with the length of the groove in the same straight line with the length of the drill-spindle, which will allow a hole to be drilled along the groove's entire length. As soon as the boss is tightly bolted in this position it is ready for drilling with a drill which has clearance enough to allow it to travel at least half way along the length of the key-way. If the boss is only one or two inches long, the drill should be capable of travelling the entire length; if not, it will be necessary to advance the drill half way, and then put the boss upside-down to drill the other half. This unfixing and re-fixing should be avoided for all small objects ; therefore the drills for such work require the proper amount of clearance referred to. The diameter of the hole which is drilled, is rather less than the width of the groove, and the place of the hole is at the bottom or extreme depth of the groove. By the hole being drilled at this place, a small portion of superfluous metal is left remaining at the intended outer edges of the groove, which portion is easily removed afterwards in a vice by means of either a hack-saw, a chisel, or files. In order that the groove may be made in its proper place, the boss, after being bored to the requisite diameter, is lined according to the mode given in page 251, which lining is suitable also for grooving bosses on shapers or planers.

To form a key-way into a boss by means of a shaper, the lever or wheel is so fixed on the table that the length of the hole is parallel with the direction of the cutting tool's motion ; consequently, one of the boss-faces is situated in front of the machine and in front of the operator. One of the boss-faces is also bolted in contact with a face of an el-chuck on the machine-table, and if a lever is being fixed, the length of it extends downwards, either near the table's surface or below it, according to the length of the lever. When attached to the chuck, the length of the key-way is put parallel to the tool's motion as required, by gently shifting the chuck previous to finally fixing it; and when this adjustment is effected it is only necessary to gradually advance the table up or down, to place the boss at the exact height for beginning the cutting. The cutting out is done with grooving tools of suitable width in their cutting edges, and all are cranked, this cranked form being requisite to obtain a long end which will reach forwards a sufficient distance to advance the tool's edge along the entire length of the hole.

If a planing-machine is to be employed for grooving a boss, the wheel or lever is bolted to an el-chuck, as for grooving with a shaping-machine; but on a planing-table the height of the chuck above the table must be sufficient to allow the entire length of the lever to stand above, unless the lever is small enough to be placed at the front edge of the table, at which place the lever may reach to the floor if necessary. If the boss is at this place, only a short el-chuck can be used; therefore the object and the chuck will not be liable to bend away from the tool while it is cutting. But when a tall el-chuck must be used, a stay should be placed to resist the strain imposed by the tool, and thereby avoid the bending referred to. The stay consists of either a piece of wood or iron which is long enough to reach from the table to the top of the chuck while the bottom of the prop is at a convenient distance from the chuck. For such a stay an iron bar is very suitable, because it can be provided with a couple of bent ends having holes

2m 2 punched therein for containing holding bolts, to fasten the stay to the table and to the chuck or object being planed.

To facilitate the adjustment of a boss to a parallel position with the tool's motion when a shaper is employed, or with the planing-table's motion when a planer is employed, the bottom edge of the el-chuck should be made to coincide with one of the gauge-lines marked on the table, a short line being selected if the object is on a planing-machine. Concerning these lines refer also to page 225.

Another sort of adjustment is necessary after placing the length of the boss into the proper position, and consists in placing the length of the lever at right-angles to the table-face, whether the object is on a shaper or planer. This adjustment will cause the key-way to extend into the metal in the required direction, which is in line with the diameter of the hole in the boss ; or in other words, in line with one of the hole's minor axes. The right-angular position of the lever is obtained by means of a primary centre line along its side which faces the operator, the line extending through the centres of the boss-faces; while adjusting the object, an el-square's blade is put to this line, and the lever is gradually shifted until the line is seen to be parallel to the blade's edge, when the lever is at right-angles to the table as required. If an el-square of sufficient length cannot be obtained or used for this purpose, the primary line along the lever is put right-angular to the table by means of a scriber-block. This is used by placing the bottom edge of the block to one of the gauge-lines on the face of the el-chuck while the scriber-point is put to the line on the lever, the point being applied to both the upper end of the line and to its lower end. The gauge-lines on el-chucks are described in page 217.

The cutting tools required for grooving a boss on a planing-machine, are similar in shape to those that are used for grooving with a shaping-machine ; the stalks of the tools being cranked forwards sufficient to advance their cutting edges along the entire lengths of the holes, in order that the upper portions of the tools may not come into contact with the faces of the bosses.

The cranked tools here referred to are represented by Fig. 704. Through the necessity of using such tools for making key-ways along the holes of bosses, when it is effected on shapers and planers, it is preferable to perform such work with slotting-machines, except when circumstances prevent a slotter being employed. A tool having a long cranked portion is troublesome to use on account of its tendency to bend while cutting, the cutting edge being at a great distance from the place or fulcrum of resistance in the tool-holder. Consequently, bosses which are comparatively short are much easier grooved with these tools than bosses of great length, because grooving tools having comparative short cranked parts are sufficient for the purpose.