Chap. XIII.

TOOLS AND MACHINES.

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cutters ; and after the screw has been cut, by placing the strap on the other outside pulley,the great internal wheel is made to revolve on the lower shaft, and draw the screw back toits original position : when the strap is put over the loose pulley in the centre, themachine does not produce any working effect, but is in the condition of perfect rest. Inthe section, the cutting of the screw is seen passing through the upper part of the chuck,and these are removable when required. The bolts which are to be screwed are held bya sliding frame, shown on the guide bolt, opposite the chuck in the elevation.

The two end views of the machine exhibit the iron frame as well as the gearing, andwhen a screw is to be formed, all that is requisite is to place the bolt in the sliding frame,and present it to the action of the die or cutter in the chuck, which, as it is turned round,forms the thread.

Fig. 1575.

Fig. 1574.

SECTION

The end view of the machine shows one of the two frames that support the works, aswell as the plummcr blocks in which the two spindles marked A, A turn : the wheel marked1J reverses the motion when it is required by the application of the loose pulley shown atE : C is the pulley which communicates motion to the spur-wheel at II: F is the frameinto which the bolts are placed which are to have their ends made into screws.

The Lathe has of late years received so many improvements, that it bears no resemblanceto the long lath or pole which was fixed at one end to the ceiling or wall of the workshop,and had the other moved by a cord passing over a pulley, and carrying the mandrell, whichwas moved by a board or treddle : on raising the foot, the spring of the lath caused anopposite rotation, which was again reversed by the pressure of the foot, causing the latheto work as a drill, the cutting taking place only during each direct rotation.

Fig. 1576. FOOT LATHE.

The lathe now consists of a horizontal bed, formed of two parallel bars of wood or metalfirmly united together : to this are attached two puppets, one of which carries the mandrelland pulley, which is fixed in its place, and the other the back centre, which slides betweenthe double bed, or along a single bar introduced for the purpose. The rest also slides onthe bed, which supports the cutting tool, and underneath is an axle with a crank; to theformer is attached a fly-wheel with a groove to carry the band, which passes over the pulleyto the mandrell; to the crank is attached the footboard by an iron bar, which produces themotion to the fly-wheel and the other parts of the lathe.

Lathes are now generally made with cast-iron sides of a triangular form, bolted orscrewed together at the iron flanches at top : the puppet on the side next the end view ofthe lathe is firmly secured by a bolt with a square head which passes through an iron

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