Fig. 2311.
In [Fig. 2311], suppose a to be a piece of wood and b and c drifts which have entered the keyways out of plumb, as shown by the dotted lines d and e. If, to right the drift c, it was struck by the hammer f in the position shown, and travelling in the direction denoted by g, the drift c would be almost sure to break; but if the drift b was struck by the hammer h, as shown, and travelling in the direction denoted by i, it would draw the drift b upright without breaking; or, in other words, the hammer face should always strike the head of the drift level and true with it, the drawing of the drift, if any is required, being done by the direction in which the hammer travels. When it is desired to cut a very smooth hole, two or more drifts should be used, each successive one being a trifle larger in diameter than its predecessor. Drifts slight in cross-section or slight in proportion to their lengths would be tempered evenly all over to a blue, while those of stout proportions would be tempered to a deep brown, bordering upon a bright purple.
For cutting out long narrow keyways, that are too narrow to admit of a machine cutting tool, and for very true holes, not to be cut out in quantities all of the same dimensions, it has no equal.
Fig. 2312.
Hand drifts are sometimes used to cut keyways in small bores, as in small hubs, the method being shown in [Fig. 2312], in which a represents a pulley with a keyway to be cut in the hub b; c is a plug, and d slips of iron placed between c and the drift e to press the latter to its cut. It is obvious that in this case the keyway in the pulley will be cut parallel, and the taper must be provided for in the key seat in the shaft. Keyways cut in this way are more true than those filed out. It is also obvious that the sides of the keyway, as well as its depth, may be finished by a drift, and this is very desirable (on account of insuring parallelism) when the key is to act as a feather that is to have contact on the sides and not bind top and bottom.
The most improved form and method of using this class of tool, however, is as follows:—If a keyway is to be cut out of solid metal, holes are drilled as closely together as the length of the keyway will admit, their diameter nearly equaling the required width of keyway, after these holes are drilled through the metal remaining between them.
Templates.—Templates for vice work are used for two purposes: first to serve as guides in filing work to shape and size, and secondly to test the finished work. When used as guides to file the work they are mainly used to work of irregular, curved, or angular form, to which the square and other ordinary vice tools cannot be applied.