Chap. XIII.

TOOLS AND MACHINES.

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dicular to this, makes another, which is the commence-ment of the mortice to contain the sheave. The sixthmachine is for mortising, and the cavities for the re-ception of the sheaves are formed by chisels in twoblocks at the same time. In the seventh, a cornersaw cuts off the angles of the blocks. The eighth isthe shaping machine, which consists of a double wheel,and contains the ten blocks at one time; when theseare put in motion, the external faces of the blockspass under the gouges, which cut them into the formrequired.

The plan of the machine shows the two wheels fittedon a common axis, which together form a chuck ; theblocks are retained by the screws; the compound wheelsor chuck, as it has been termed, receive a rapid circularmotion from an endless rope, which passes over thepulley on the axis ; and the blocks can be operatedupon in any way required, by presenting the gougeor cutting-tool, which traverses a seginei tal bar bymeans of a slide rest. The workmen guide the cuttinginstrument to any part of the surface, as it revolvesby handles, and thus cut it into shape : after the edgesof the blocks have been taken off, the machine isstopped, and they are turned round one quarter ontheir respective axes, presenting another side as thewheels revolve, and, in a similar way, they are againand again turned until they receive their complete form.

The large bevelled wheel next the pulley wheel turnstwo other bevelled cog-wheels fixed on a rod, at theend of which is an endless screw, with the axis tendingto the centre of the chuck. On the large wheel is a ,.- igi 1602 . block-making machine.pin projecting from its circumference, which is detained

by means of a stop that occasionally presses the pin, and turns the chuck round on a fork,which stops the motion of the wheel; it is then that the attendant workman, by means ofthe endless screws, places the blocks in a proper position to be cut by the gouge.

Fig. 1603

BLOCK-SHAPING MACHINE.

The ninth is the scoring engine, for cutting the groove round the largest diameter for thereception of the strap of the block ; thus the shells of the blocks are prepared, after whichthey are trimmed, polished, and finished by hand.

The machines for mak ing the sheaves are the next, and the tenth is the straight saw,employed to cut the lignum vitae.

The eleventh is a circular saw, employed when smaller sheaves are required.

The twelfth is the crown saw, which works similarly to a trepan, having a centre bit onits axis : it is used for cutting out the circle, and at the same time the hole in thecentre.

The thirteenth is the cooking engine, which cuts the cavity in the centre of the sheavefor the reception of the cook or metal bush.

The fourteenth is the drilling machine, which is applied to perforate the three semicir-cular projections of the coaks, at the same time drilling through both the coaks and thewood of the sheave.

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