62 



Improved screw-wrench. 



I have, for several years, been intrusted with the care ant! 

 repairs oi many valuable engines of various descriptions, 

 composing the block machinery in this dock-yard, and I 

 have always considered it as an object of great importance, 

 for the preservation and neat appearance of engines, to 

 attend to all the means which would obtain these advan- 

 tages, and such, I think would arise from the use of my uni- 

 versal wrench. 

 May be made It is, perhaps, unnecessary to point out, that a wrench oft 

 of various sizes. t |,j s principle may be varied in its form and size so as to be 

 rendered probably more convenient for some particular pur- 

 poses for which such instruments are required. 

 1 am, Sir, 



Your obedient servant, 

 Portsmouth Dock Yard, WM. BARLOW. 



March 1, 1808* 



The instru- 

 ment de- 

 scribed.. 



This instrument is represented in PI. IT. Fie. 5 is a 

 perspective view of it ; fig. 6 a section of its head ; and fig. 

 7 an external representation of the head. The screw head 

 or nut to be turned is held between two jaws, one of which 

 a b d e is forged in the same piece with the handle A A, the 

 ©ther,/g-, i s moveable between two chukes, and fastened to 

 the fixed jaw by the strong screw i, which is fixed to the 

 same jaw, passes through the, moveable one, as shown in 

 the section fig. 6, and has a nut screwed upon it ; the 

 other screw h, is tapped through the movable jaw, and its 

 point presses upon the bottom of a cavity made in the fixed 

 jaw shown at m in the section fig. 6. To make the wrench 

 fit any particular screw head or nut, the nut upon the strong 

 screw i must first be loosened, and the screw A screwed in 

 or out of the movable jaw, until the opening b g is just 

 the proper width to receive the screw head or nut to be 

 turned by the wrench ; the nut of the screw i is then to be 

 screwed down, until it presses upon the jaw, and holds it 

 perfectly tight. 



XIII. 



