BLOCK MACHINERY. 



611 



Block Ma- 

 chinery. 



Circular 

 cross cut- 

 ting saw. 



fresh cut. The lump of wood before mentioned can 

 be fixed at any place along the platform, so as to cut 

 any required length off the end of the tree. It should 

 be mentioned, that a lever is placed across the end 

 of the tree ; one end turning on a pin fixed in a firm 

 post, and the other so loaded, as to keep the piece 

 steady upon the bench when it is nearly or quite cut 

 through. The under side of the lever is fitted with 

 large teeth, which penetrate into the tree and hold it. 

 This is a very simple and effective machine ; but does 

 not cut so quickly as the circular saw which follows, 

 because it does not admit of such a rapid motion ; but 

 it can be constructed to cut trees of very large di- 

 mensions at a small expe'nee. 



The circular cross cutting saw. The reader must 

 figure to himself a frame formed of two long parallel 

 spars of wood, united by cross bars and braces ; this, 

 which we call the saw frame, is suspended vertically 

 by one end, where it is jointed to the end of a similar 

 frame, (say the upper frame,) poir.vd nearly horizon- 

 tally, on an horizontal axis which passes through it 

 near the middle of its length. The end opposite that 

 which supports the saw frame is loaded, so as to coun- 

 terpoise its weight. At the lower end of the saw frame, 

 the spindle of the saw is mounted, by its bearings be- 

 ing bolted on the spars of the frame. The saw is fixed 

 on the extreme end of the spindle, so as to be on the 

 outside of the spars. The spindle is parallel to the 

 axis of the upper frame. The tre is placed on a 

 bench, and drawn up to a stop by a windlass, just the 

 same as in the foregoing machine, and is kept steady by 

 a crooked bar in a similar manner. The tree lies in a 

 direction parallel to the axis of the saw. Now it will 

 be seen by this arrangement, that the saw possesses 

 universal motion ; but the axis is always parallel to 

 itself, and the saw in the same plane. It can be raised 

 up or lowered down, by inclining the upper frame on 

 its axis ; and to move it sidewise, the saw frame must 

 swing sidewise on its joints, which connect it with 

 the upper frame. These movements are effected by 

 two winches, each furnished with a pair of equal pi- 

 nions, working a pair of racks fixed on two long poles. 

 The spindles of these winches are fixed in two vertical 

 posts, which support the axis of the upper frame. One 

 of these pair of poles are jointed to the extreme end 

 of the upper frame ; therefore by turning the handle 

 belonging to them, the frame and saw is elevated 

 or depressed : in like manner, the other pair are at- 

 tached to the lower part of the saw frame, so that 

 the saw can be moved sidewise by means of their 

 handles, which then swing the saw from its vertical 

 position. 



These two handles give the attendant a complete 

 command of the saw, which we suppose to be in rapid 

 motion, the tree being brought forwards and properly 

 fixed. By one handle, he draws the saw against one 

 hide of the tree, which is thus cut into, (perhaps half 

 through ;) now, by the other handle, he raises the saw 

 up, and by the first-mentioned handle he draws it a- 

 cross the top of the tree, and cuts it half through 

 from the upper side ; he then depresses the saw and cuts 

 half through from the next side ; and lastly a frilling 

 cut of the saw, as the lower side completely divides 

 the tree, which is then advanced to take another cut. 

 The strap for the saw is conducted over pullies, 



two of which are fixed on the upper frame near its ho- Ulock Ma. 

 rizontal axis; and it then turns a pulley, fixed on an c '" uor y- 

 axis concentric with the joint, connecting the two 



large frames. On the same axis is another equal pul- 

 ley, around which the strap is passed, which turns the 

 pulley on the spindle of the saw. By this means, the 

 strap never becomes slack in any movement of the 

 saw, as its points of flexure are the same as the 

 frames. This machine is very ingenious, and acts with 

 great accuracy, and astonishing rapidity. 



The great reciprocating saw is on the same prin- The great 

 ciple as the saw mill in common use in America, at reciproca. 

 least the differences are so small, that they cannot be tms saw " 

 explained without drawings ; and as this machine is 

 by no means essential to the manufacture of blocks, 

 we shall refer our readers to the article Sawing Ma- 

 chinery. ' 



The circular ripping saw, is a thin circular plate The circu- 

 of steel, with teeth similar to those of a pit saw, form- lar ripping 

 ed in its periphery. It is fixed to a spindle placed saw. 

 horizontally, at a small distance beneath the surface 

 of a bench or table, so that the saw projects through 

 a crevice a few" inches above the bench. The spindle 

 being supported in proper collars, has a rapid rotatory 

 motion communicated to it by a pulley on the opposite 

 end, round which an endless strap is passed from a 

 drum placed overhead in the mill. The block cut 

 by the preceding machine, from the end of the tree, 

 is placed with one of the sides flat upon the bench, 

 and thus slides forward against the revolving saw, 

 which cuts the wood with a rapidity incredible to 

 any one who has not seen these or similar machines. 

 The wood is guided in its progress toward the saw 

 by a large parallel ruler, similar to that used for 

 drawing, which can be placed and fixed at any re- 

 quired distance from the plane of the saw, but is al- 

 ways parallel to it : by this means the circular 

 saw becomes a general machine, and can be adapted 

 to cut any required width. Its great advantages are, 

 the saving of labour, and the great accuracy of its 

 performance, as it invariably cuts a perfectly plane 

 surface ; and it is evident that any number of pieces cut 

 by it must be of precisely the same size, wheii the 

 parallel ruler remains fixed at the same point. This 

 is an important circumstance in these works, as the 

 accurate performance of many, or indeed all the ma- 

 chines, depends upon the blocks which are submitted 

 to them, at the same time, being of one size. We have 

 not given these sawing machines among our Plates 

 in this article, because this saw is in constant use for 

 sawing in general, and will therefore come more pro- 

 perly under Sawing Machinery, where we pro- 

 pose to explain this, or a similar one constructed by 

 Mr Maudslay, who has a peculiar mode of making 

 the collars for the axis of the saw, which succeeds 

 remarkably well. It is a great improvement upon 

 the usual mode of fitting up the circular saw, and 

 which, we believe, was first introduced (at least for 

 sawing large timber) by Mr George Smart of Lon- 

 don. In the old method, the ends of the spindle 

 were perforated with small conical holes, and the 

 conical points of two fixed screws were inserted into 

 them. All the points of contact were made of steel, 

 and hardened. Nothing could be more perfect or easy 

 than the movement of 6uch a spindle, until it waa 



