Fig. 11 is taken from an old wood-cut of the mortising machine.[28] A model of it is shown in the background of the portrait of Brunel in the National Gallery, reproduced opposite page 26. A pulley and flywheel are connected by a cone clutch _M_ to a shaft _D_. At the front end of this a crank and connecting-rod drive the reciprocating cutter head from a point _a_. The chuck carrying the block, movable forward and backward on guides, was operated by the feed screw _R_, a cam, and the ratchet motion shown. A system of stops and weighted levers on the side threw out the ratchet feed at the end of the cut, and the carriage was returned by hand, using the crank _r_. The crosshead had two guiding points, a double one below the driving point and a single one above it at _F_, and made 150 strokes per minute. The chuck could take either one or two blocks at a time. [28] Tomlinson: “Cyclopedia,” Vol. I, p. 141. Fig. 12 shows the shaping machine.[29] _Ten_ blocks were chucked between two large, circular frames, the same working points being used as in the last machine. The principle of establishing and adhering to working points seems to have been clearly recognized. A cutter _g_ was moved across the face of the blocks as they revolved, its motion being governed by the handles _l_ and _G_ and a former _i_. One side of each of the ten blocks was thus finished at a time. The blocks were then indexed 90° by revolving the bevel _K_, which turned the wormshafts _d_ and rotated all the chucks simultaneously. The blocks were then faced again in their new positions and the operation continued until the four sides were finished. The strong curved bars at the top were provided to protect the workman in case one of the blocks should let go. As the momentum of the frame and blocks was considerable, a spring brake was provided between the bearing and bevel-gear to bring them to rest quickly. [29] _Ibid._, Vol. I, p. 144. [Illustration: FIGURE 11. BRUNEL’S MORTISING MACHINE] [Illustration: FIGURE 12. BRUNEL’S SHAPING MACHINE] Another well-designed machine “scored” the outside of the blocks for the ropes or straps. Two disks with inserted steel cutters grooved the blocks which were chucked on a swinging frame. The depth and path of cut were governed by a steel former against which a roller on the cutter shaft bore. In the metal working machines, under the fourth group, cutters were used in which a short, round bar of tempered steel was held by a binding screw in a holder of the lathe-tool type. From the sketch of it shown by Holtzapffel, the whole device might almost be used as an advertisement for a modern tool-holder for high-speed steel cutters.