In addition to the modes of forming slots by planing, given in the preceding section, it is requisite to mention a few other methods of slot-making, which are resorted to in cases of emergency.

A small guide that requires a slot of only a few inches in length, can be slotted on a shaping-

2q2 machine. The article can be lined by the same methods as those given for a guide situate on a lining-table, or for one on a planing-table, the only difference consisting in adopting the shaping-table or tables as standard planes to which the work is adjusted, instead of adjusting it to a planing-table.

A guide-standard on a shaping-machine can be entirely shaped with three fixings, which are analogous to the three fixings of a larger guide on a planing-machine ; the two broad sides and the foot being shaped with the first and second fixings, and the entire slot being formed at th<.-third. The placing of the broad sides upon parallel blocks, the attachment of the plates, and the tools used for removing the metal, are also the same as if the guide were to be planed.

The formation of a guide-slot on a slotting-machine, is executed after the standard has beep previously planed with a planing-machine, to reduce the broad sides to proper dimensions and make them parallel with each other. Although a slotting-machine is not suitable for planing these sides, the outer extremity of the foot can be easily planed with a slotting-tool; for which purpose, it is necessary to adjust the centre length of the slot to parallelism with that traverse of the slide-rest which is square to the machine-front. Such adjustment causes the outer surface of the standard's foot to be parallel with the front; and therefore allows the standard to be advanced in this same direction during the removal of the metal. To allow the releasing motion of the tool during its upward travel, the surface to be planed is situated between the tool and the front; so that, if the operator now stands at this place, the length of the slot-portion extends from the foot or bottom towards him.

After the foot or bottom is surfaced, the formation of the slot may be effected while the standard yet remains in the same position on the table. But the slide-rest traverse which is to be now used, is the one at right-angles to the machine-front. During the slotting, the guide is moved from the front of the machine towards the main-standard; for which reason the tool will commence to cut at that end of the slot which is nearest to the main or F-standard. The other traverse of the rest, parallel with the front of the machine, by which the foot was surfaced, is now only used to adjust the object exactly to the tool for removing a slice of a certain thickness; therefore, after this adjustment, whenever a slice is to be commenced, the traverse screw is fixed to prevent an unintended movement and consequent mischief.

A guide-slot which is to be shaped on a slotting-table, is provided with a clearance space at each end, the same as if it were to be planed; therefore ample room exists for the slotting-tool to retreat back from the metal while the end of the slot nearest the tool is being shaped. The tools employed are the slotted ones, which admit cutters of any length and shape to suit the width of the slot to be formed. (See Figs. 786, 787, and 788.) The solid tools having bent ends, denoted by Figs. 793 and 794, are also available. A quick mode of shaping a slot consists in causing a tool to cut both faces of the slot at once. This plan is suited to any guide which requires its slot to be rapidly although roughly formed. If the article is strong, and properly supported with packing-blocks, to sustain the comparative severe strain while the tool is cutting, a considerable amount of time may be economised. It must be remembered that the action of any slotting-tool has a much greater tendency to break the guide, than the action of a shaping-tool or planing-tool, by reason of the slotting-tool's motion being square to the guide's broad sides. Consequently, when a slot is to be formed by a tool cutting both sides at once, only a thin strip of metal should be cut off at each travel of the tool. While a guide is being slotted, it should be supported on packing-blocks of great length, their length being, if convenient, as long as the slot; and they require to be close to the intended mouth of the slot when finished, allowing only a sixteenth of an inch between each block and the slot's edge. Blocks thus placed afford great resistance to the tool in addition to preventing the breakage of the standard.