This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
The faults inherent in all forms of awl, gimlet, and auger are that the rotation is necessarily interrupted to enable the position of the hand or hands to be changed, and that the pressure exercised on the tool is in most cases limited. These drawbacks are overcome by the brace and its accompanying bits. The ordinary form of brace is shown in Fig. 3S1. It consists simply of a crank, one end a being provided with a round head for receiving pressure from the breast of the workman, the other end b recessed for the introduction of the bit, and the centre c rendered smooth for the application of the hand that turns the whole. It will be obvious that much greater working efficiency can be got out of the boring tool by the continuous rapid rotation and heavy pressure secured by this implement than by the simpler forms previously described. The tools adapted for use with the brace (Figs. 382-394) are made fast in the end b by means of a thumb-screw catching in the notch seen near the end of their stems. This constitutes the weak point in the ordinary form of this compound tool.
In the first place, the use to which the implement is subjected has a direct tendency to wear the thumb-screw in such a degree as to soon render it loose and incapable of holding the boring tool firmly; and in the second place, the square hole in the end b is of fixed size, and will only admit tools which fit it accurately. These defects are remedied in Barber's patent brace, which is provided with an expanding chuck that adapts itself to all shapes and sizes of stems, and holds them tight and true. It is made in several sizes and styles, the most useful being the 9-in., costing 3s. 6d.; the common socket iron brace of the same size may be had for about 1s. 6d. Of the tools employed in the brace, Fig. 382 is a centre-bit, useful for boring large and deep holes; Figs. 383, 384, 385, countersinks for enlarging the entrances of holes when it is desirable to let the screw or other occupant of the hole lie completely beneath the surface of the wood - they are termed respectively " snail-horn," " rose-head," and " flat-head," from their shapes; Fig. 386, a screwdriver; Fig. 395, a bobbin bit; Fig. 387, a taper bit, for boring funnel-shaped holes; Fig. 388, a sash bit; Fig. 389, a shell bit; Fig. 390, a nose bit; Fig. 391, a spoon bit; Fig. 392, a square rinder; Fig. 393, a half-round rinder; Fig. 394, a gimlet bit; Fig. 396, a dowling bit.
Many other forms might be mentioned, including those employed in metal working, for which the implement is equally well adapted.