The gaps of solid fork-ends, connecting-bars, cranks, and similar articles which are to be shaped by hand, should be formed with the aid of drilling. Such drilling consists in making holes at the bottoms of the intended gaps, the drilling being done next after lining, and previous to any other shaping. The intended fork-end of a connecting-bar is shown by Fig. 805, which denotes a solid lump marked with a dotted line showing the place and dimensions of the gap to be formed. At the bottom of the gap a circular hole is to be drilled, and so situated that its edge shall exactly coincide with the intended bottom, thus leaving no metal to be afterwards removed by chiselling, the bottom being properly shaped to the curve required by the rotation of the drill. When drilled, the cutting out of the superfluous lump proceeds by making two deep grooves with grooving-chisels, the grooves being situated close to the dotted line, and extending downwards along the entire length of the gap to the drilled hole. By such grooves, in conjunction with a previous drilling, the entire gap-piece is removed, and the bottom of the gap nicely shaped.

Fig. 806 represents a crank-axle having a crank-lump, the gap of which is to be made by the same means as that mentioned for a fork-end, with the difference of drilling three or four holes along the bottom of the intended gap, instead of only one. These holes are of small diameter, because they are required only to partly separate the gap-piece, and not to shape the crank-gap to its finished form, as while drilling the gap of a fork-end rod.

Instead of cutting out gap-pieces with grooving-chisels, sawing may be adopted for making the cuts. The saws used for this and similar purposes are of various classes, some being worked by hand and others by steam. The simplest class of saws for hand use are those termed hack-saws. A hack-saw for engineering purposes is one of fourteen or sixteen inches in length, and about a twentieth of an inch in thickness, which is attached to a holder or frame, and properly stretched with a screw-nut, to prevent the saw bending while in use. One end of the frame has a wood handle resembling a file handle, which is gripped in the right hand while the tool is in use. The mode of using it consists in moving it to and fro in contact with a piece of metal, in a manner similar to that of using a file, until the saw-cut is deep enough, or until the piece is cut off, according to circumstances. A hack-saw is very suitable for iron, brass, and gun-metal, and will cut easily and quickly while the article being sawn is firmly held in a vice which will not shift during the sawing.

Circular saws are also employed for making gaps, and are actuated by proper sawing apparatus. Band-saws are also very useful, especially for large objects.