There are several modes of forming key-grooves, and any one mode selected should be suited to the characters and dimensions of the objects to be grooved. Either lathes, shapers, slotters, or planers are employed, according to the particular class of macnines that may be available.

Small key-grooves for spindles and shafts which are not more than two or three inches in diameter, are quickly and easily formed in a lathe by means of a grooving tool which is tightly held in the slide-rest and moved to and fro in contact with the piece to be grooved, which piece is fixed on the lathe-pivots. When a groove is to be cut by this means the spindle is first properly turned, and next lined while situated on vee-blocks, or by other means, to correctly show the place and shape of the key-way required; after which it is again put into the same lathe, or into another one, in the same position as it previously occupied while being turned, a gripper being fixed at the end which is near the chuck, that the spindle may be secured and prevented from shifting when not required. If the groove is to be made into a collar-portion of the spindle, or into some portion which is considerably larger in diameter than the portions immediately adjoining, the piece is ready for grooving without any drilling. But if a groove is to be made into an end of the spindle, or into the mid-part of a spindle which is parallel, it is requisite to drill a preliminary hole previous to beginning the grooving, the hole being necessary to provide a space into which the end of the cutting tool may extend. If the key-way is to be at one end of the spindle, only one hole is drilled, and is situated at the inner extremity of the intended groove, which is that end furthest from the extremity of the spindle. The hole is so drilled that its diameter and depth are the same as the width and depth of the groove to be cut; consequently, an amount of space is provided which allows the tool to move freely to an extent which equals the groove's width. A space of this kind is sometimes provided at both ends of the groove, the two spaces being necessary when the key-way is to be made in the mid-part of a parallel piece before referred to. If the groove is in such a part, room must be provided for the tool to enter the metal at one end and to escape at the other end.

When the spindle is prepared by drilling, it is tightly fixed on the lathe-pivots by tightening the poppet-screw, and the grooving tool is fixed at a proper height in the slide-rest. In order to place the groove exactly to the tool, the lathe-band is moved a short distance to partly rotate the piece; after which the tool is advanced by rotating the slide-rest screw. The cutting now proceeds by moving the rest and tool to and fro, gradually advancing the tool into the metal a proper distance each cut. Small grooves that may be only about a quarter of an inch wide can be formed with only one tool, the length of whose cutting edge is equal to the width of the groove. For larger grooves it is proper to commence with a tool which is narrower than the groove, and afterwards use one or two wider tools to make the groove of a proper width. While finishing a groove by such a process it is necessary to use a tool the cutting edge of which is as long as the width intended, because if the spindle were rotated a short distance to make a narrow tool cut at one side, the groove would thereby be malformed, because the direction in which the tool would enter the spindle would not be parallel to that in which it entered at the beginning of the cutting. Concerning the shapes of key-grooves, refer also to pages 251 and 252.

The mode of properly adjusting the tool to make it advance into the spindle in the proper direction, consists in packing it up with pieces of sheet steel of suitable thickness until the centre of the tool's cutting edge is at the same height above the lathe-bed as the centres of the lathe pivots. To ascertain whether the tool-edge is at this height, it is necessary to place the height-gauge belonging to the lathe upon the bed, with the centre mark near the tool-edge, and then to observe its height, which will indicate the amount of packing necessary. Instead of the height-gauge a scriber-block of suitable height may be used. This adjustment should be done for all the tools that may be used for one groove, whether they are used to begin the groove or finish it.

A large key-way that may be of twelve or fourteen inches in length and two and a half in width may be made with a planing-machine, the shaft or axle to be grooved being fixed on the table. If a large shaft is to be thus grooved it is necessary to drill a preliminary hole at the inner end, as for grooving with a lathe, in order that the tool's edge may not break by coming into contact with the inner extremity. It is also necessary that the stops at the table's edge be accurately fixed in their proper places to cause the table and work to travel to the exact place desired, such adjusting of the stops being done after the shaft is finally fixed to the table. The planing of a wide groove of this sort should commence with narrow grooving tools, with which a narrow groove is made at each edge of the intended key-way, thus forming a ridge of metal in the middle. This ridge is next cut out with an ordinary vee-point facer having a comparative thin end, which end will allow the tool to reach the bottom of the key-way and travel across it with the machine's traverse, without causing the thicker part of the tool to touch the sides of the key-way. By this cutting out with such a thin end, after two grooves have been previously made, the key-way is roughly shaped to nearly the finished dimensions, and is ready for being finished smoothly to the exact size required with corner tools and with soapy water.

Through the necessity of first drilling a hole at the inner end of a large key-way which is to be planed, it sometimes happens that the entire groove can be quicker formed by drilling than by planing. In the case of a large shaft requiring to be moved from place to place without proper railways, it is better to make a number of holes along the place of the key-way, while the shaft is at the drilling-machine, instead of making only one at the inner end. Either one row of large holes may be made, or two or three rows of comparative smaller ones, the particular diameters of which depend on the width of the key-way. Such drilling should be done with two classes of drills, one of which is the ordinary point-drills, which are specially furnished with short points, to drill the bottom of the groove nearly flat; and the other class are pin-drills, which for this purpose are provided with very thin pivot-pins. These pin-drills are to be used after the holes are drilled with the ordinary drills as deep as their large conical points will permit, when the holes are ready for the pin-drills with small pins, which are made to cut out what metal remains at the bottoms of all the holes, and which could not be removed with ordinary drills without making the key-way deeper than necessary. After the drilling is done, the superfluous metal remaining between the holes is removed either with grooving-chisels or with planing-chisels, according to the thickness of metal to be chiselled. This chiselling can be done while the shaft yet remains at the drilling-machine, therefore all trouble which would result from moving it over rugged floors is avoided, and the adjusting and fixing on a planing-table also is avoided.