MECHANICS AND USEFUL ARTS. Ill 



chinery for threading wood-screws, has been patented one whose cut- 

 ter is somewhat like the fusee of a watch, with the difference that the 

 grooves are in three sections, parallel to its axis, counterparts of the 

 threads of the screw to be cut, and that these grooves are deeply 

 notched or serrated, so as to form a series of cutters. This cutter has a 

 swift revolution on its axis, and its periphery revolves in contact with 

 a blank, properly supported and presented to it ; the blank also, re- 

 volvino- in the same direction as the cutter, and having a slight motion 



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in the direction of the axes of the cutter, is gradually pressed against 

 its periphery, so as first to mark, then to deepen, and finally to finish, 

 its thread. These are the main characteristics of the machine, which 

 is provided with many other ingenious contrivances, subordinate, in- 

 deed, to the general principle, but essential to its prompt and correct 

 action. The rapidity with which this machine performs its work, and 

 the accuracy and beauty of the screws made by it, are equally won- 

 derful. 



Thimble Machine. A machine which forms perfectly the thimbles, 

 so termed, used in large quantities in the rigging of vessels, has been 

 patented. These thimbles are metallic rings, or short cylinders, whose 

 outsides are grooved, and whose insides are convex to the same extent 

 that the exterior is concave. In the machinery for making them, two 



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shafts are so arranged as to revolve at the same time and in the same 

 direction, and have a common axis. Thev are also so fitted that, while 







revolving, they can be made to approach or recede from each other. 

 The contiguous ends of these shafts are each provided with a forming 

 disk, whose diameter is least upon that side of it which is at the end 

 of the shaft, and gradually increases in a concave curve to the other 

 side, which is of a diameter equal to the greatest inside diameter of 

 the thimble to be formed. Each disk exactly fills one half of a finished 

 thimble, and when their adjacent sides are, by the motion above as- 

 cribed to the shafts, brought in contact, thev entirelv fill a finished 



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thimble. A hammer, whose face is an exact counterpart of about one 

 quarter of the outside of the thimble, is arranged in such manner as 

 to strike repeated blows upon a piece of iron sufficiently heated, and 

 thrust in between it and the disks above cited. 



In the working of the machine a lever is moved which brings the 

 disks in contact. A piece of iron, in length equal to the circumfer- 

 ence of the thimble to be made, is then introduced between the disks 

 and the hammer. The disks then revolve, and the hammer forces the 

 iron into the groove, and at the same time bends it into a circular 

 form. 



As the disks revolve, new surfaces are brought under the action of 

 the hammer, and a thimble is finally formed, closely enclosing the two 

 disks. These are then separated by the action of the lever, and, as 

 they revolve on horizontal shafts, the finished thimble drops down be- 

 tween them. 



The thimbles formed by this machine are not only cheaper, but 

 better finished, smoother, and more regularly shaped, than those made 

 by hand, 



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