Chap. XIII.

TOOLS AND MACHINES.

1037

wheel was 5 teet 8 inches in diameter, and the small one 2 feet 8 inches : the transversepart of the machine is shown below, as is the end of the spindle and cutter: the wholewas put in motion by means of two winches or handles and an endless chain.

Shears for cutting Iron or Copper either into square plates or lengths are formed in asimilar manner to those for punching the metals, except that the motion given to the cuttingpart of the shears acts very gradually, by means of a circular eccentric. The lever hasa wheel at its extremity, which moves on its axle ; on the edge is a groove in which the

Fig. 1589. SHEARS FOR CUTTINO IRON,

edge of a larger wheel works, which has the axle out of the centre; so that when therotary motion is communicated, the movable branch of the shears opens and shuts, theweight of the lever keeping the small wheel at all times in contact with the eccentric; bythis means very stout iron bars are easily cut asunder.

Slotting or key-grooving Machine somewhat resembles one made use of by Messrs. Boultonand "Watt at Soho forcutting the teeth ofwheels.

Slotting, paring, andkey-grooving, requirethat the machine shouldhave an alternate orreciprocating motion,which is usually pro-duced by a crank ordog wheel. The ma-chine a is made usuallyof iron, and the powerapplied to the drivingriggers b , which are re-gulated by a fly-wheel £c .• and the speed isgoverned or changedby the action of a spur-wheel and pinion. Thetool fixed at * is keptsteady by screws at h, inthe sliding frame, andthe work to be operatedupon is placed in theslide k.

There is a self-actingapparatus, by which thework is advanced at m, Fig ,and a revolving table for circular work at 7.

Screw-cutting Machine is formed upon the principle of the lathe, its bed and puppetsbeing made of cast-iron ; at one end tw*o bevelled wheels fit on a part of an axle, which mayhe thrown in or out of gear by means of another bevelled wheel at the side, which is put inmotion either by the power of a steam-engine or water-wheel.

The screw to be cut is shown in the middle of the machine ; the slide-rests, which containthe cutters of the threads, are moved forwards by the motion of the conical wheels at theend ; as these slide-rests pass from one end of the frame to the other, they enable the cutterin its progress to form the thread in the revolving cylinder: when the frame has arrivedat the end of the bed, it presses against a stud, to which is attached a small lever thatthrows the wheel out of gear ; the cutting tool is again placed at the commencing end bythe workman, its motion is reversed, the tool is re-adjusted, a deeper cut is made, and thisis continued until the whole operation is performed.

SLOTTING MACHINE.