BLOCK MACHINERY. 



609 



smooth, but because this process cannot derive any 

 assistance from machinery, while the expense of la- 

 bour in the machine work is so exceedingly small. 



We now come to enumerate those machines em- 

 ployed for making the sheaves. The wood for these 

 is cut from a tree of lignum vitoe, across the grain, so 

 as to form pieces approaching to a circular figure, 

 and nearly the thickness of the intended sheave. 

 These pieces are cut by two machines. The first of 

 these, 



No. 10. The straight saw, for converting the lig- 

 num vitse. This is constantly moving backwards and 

 forwards by the machinery, in a horizontal plane. 

 The tree of lignum vitx is fixed vertically, and raised 

 so much above the plane of the saw as the thickness 

 of the intended sheave ; and the saw being applied 

 to the wood, quickly cuts it through, separating a 

 piece from the end of the tree, just the true thick- 

 ness to form the sheave. This saw is appropriated 

 to cutting out the largest sheaves, because the circu- 

 lar saw, to be next mentioned, would not act freely 

 through a large and hard substance. 



No. 1 1 . Thecircularsau: is for the same purpose, but 

 is applied to the smaller sheaves. The tree is, as in the 

 former instance, fixed in a vertical position, but upon 

 the end of a spindle, in such a manner that it can re- 

 volve upon its own axis, and the circular saw ha3 its 

 axis placed vertically, and mounted in a frame which 

 moves upon a centre, so that the saw moves in an arc 

 of a circle, but still continues in the same plane. The 

 saw, as it revolves, is applied against the tree, by mo- 

 ving it in its arc, and cuts off a thin plate. These 

 plates are now sorted out as to the sized sheave which 

 each will make with the least waste : They are then 

 carried to, 



No. 12. The crown saw. This is a saw similar to 

 a trepan, and having a centre bit in the axis of it. 

 The piece of wood being fixed by a neat contrivance 

 before this saw, it is applied against the wood, and 

 quickly cuts out a circle, and at the same time forms 

 the centre hole, exactly in the centre of it. 



No. 13. The cooking engine is perhaps the most 

 ingenious of all these machines. It forms, by means 

 which we cannot describe without the drawing, the 

 cavity in the centre of the sheave for the reception of 

 the coak or metal bush. This cavity is in the form of 

 three small semicircles, arranged at equal intervals 

 round the circular holes formed in the last machine. 

 Two of these engines are used. The sheaves are 

 cut by this engine, first on one side for one of the 

 coaks, and they are then turned to have the other cut. 

 The coaks are now inserted into the cavities cut by the 

 coaking engines. They are cast of a mixture of copper, 

 zinc, and tin, called gun metal, to the true shape at 

 once, by means of an accurate pattern moulded in sand. 

 No. 14'. The drilling machine is applied to perfo- 

 rate the three semicircular projections of the coaks ; at 

 the same time it drills through both the coaks and 

 the wood of the sheave. The copper pins, which are 

 put into these holes, are cut from the proper sized 

 wire, by a simple tool fixed in the vice, all the same 

 .length. The pins being inserted into the holes, are 

 carried to, 



No. 15. The rivelting hammers, two small tilt 

 hammers put in rapid motion by the machinery, for 

 VOL. III. PART IV, 



the purpose of rivetting the pins which hold the gun Block Ma- 

 metal coaks into the cavity in the sheaves, made by c! " 

 the coaking engines. These hammers, also, by pres- 

 sing on a treddle, can strike a heavier blow towards 

 the end of the operation. The sheaves in this state 

 are carried to, 



No. 16. The broaching engines, of which three 

 are used. The sheave is fixed to a vertical revolving 

 axis, and the borer is brought down into the hole in 

 the centre of the coaked sheave, and broaches it out 

 to a perfect cylinder. The sheaves thus formed, re- 

 quire only to be turned in, 



No. 17. The face turning lathe. This i3 an ex- 

 cellent lathe, provided with a sliding rest, which sup- 

 ports the turning tool, and moves it slowly across the 

 face of the sheave, which is fixed upon the end of the 

 spindle or mandrel of the lathe, and turned round 

 thereby. 



The blocks, shells, and sheaves, being now finish- 

 ed, we have to consider the iron pins for them. The 

 small blocks, indeed, are fitted with pins of hard 

 wood. The iron pins are first forged to the true size 

 and shape, having a cylindrical part of sufficient 

 length to pass through the shell of the block ; and a 

 square part, which is to be drifted into one of the 

 cheeks of the shell, to prevent the pin from turning 

 round. They are then taken to, 



No. 18. The turning lathe, where the iron pin? 

 are turned by a slide rest, in a manner something si- 

 milar to the facing lathe : they are then covered with 

 spiral scratches from the scoring of the tool. These 

 are rounded by, 



No. 19. The polishing engine. The pin is fixed 

 into the lower end of a vertical revolving axis, and 

 forced down into a sort of die, immersed in oil, hold- 

 ing three pieces of hard steel, between which the pin 

 is pressed as it turns, and by that means is perfect- 

 ly polished. 



The wood pins are cut by the circular saw into oc- 

 tagon pieces of the proper length. These are put 

 into a common lathe, having adapted to it a simple 

 tool, called a wilchit, which quickly cuts the pin to a 

 true cylinder, except a short piece at the end, which 

 is left of an octagon form to be inserted into the 

 cheek of the block, in order to prevent the pin from 

 turning. We have not numbered this as a separate 

 machine, because it is used in the common way of 

 making blocks, being applied to the same lathe in 

 which they turn the sheaves. 



Besides all these machines, the block mills contain 

 three others ; one for large blocks, and two for dead 

 eyes. 



No. 20. The former is a complete apparatus for bo- 

 ringvery large lioles'm any position. It is used for blocks 

 of a size beyond what the regular machines are calcu- 

 lated for ; some of these blocks being as large as S4> 

 inches in length, with 4 sheaves. The shells for these 

 are made up of pieces. They are used for the mast 

 hulks ; and by them the masts of the largest ships are 

 suspended while they are fixed in their situation. The 

 number of these blocks which is required, is not so 

 great as to make it worth the expence of a set of ma- 

 chines for them ; but the workmen avail themselves 

 of all the assistance which they can derive from the 

 largest of the three sets of machines, and perform the 

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