DESCRIPTION OF THE DIVIDING ENGINES 695 



filled with, oil is to dampen any vibrations of the frame which carries 

 the diamond, and to check its descent on the plate. 



IV. Corrector mechanism. See Figs. 1, 4 and 5. 



The wear of the threads contained in the lignum vitas plugs of the 

 split nut-casing is taken up by the screws in the adjusting rings (17), 

 bringing the two parts of the nut closer to the feed-screw. Each side 

 of the nut is provided with a wing-shaped lever, the lower ends of which 

 are confined in guides forming part of the lower corrector frame (39); 

 but they are free to travel in the direction that the nut moves. When 

 the screw is turning and the nut advancing, these wings are pressed 

 tight against the guide-plate (39 A) of the corrector frame; and thus 

 the nut will receive additional motions from any displacement of the 

 corrector. In this manner periodic errors of the screw may be neutral- 

 ized by the action of the corrector. The precise amount of correction 

 is controlled by the adjustments of the eccentric (25). This gives the 

 requisite amount of movement at the proper instants to the corrector 

 lever (28), which in turn moves the rocking shaft, corrector frame, 

 crank, lower frame and, finally, the wings of the nut. The disc (24) 

 may be adjusted and clamped, as shown in Fig. 4, in different positions 

 in the plane of the graduated ratchet-head; and the position of the 

 corrector eccentric (25) with respect to a fixed radius of the graduated 

 ratchet-head must be such as to make the phase of the correction oppo- 

 site that of the periodic error. The amount of eccentricity of the eccen- 

 tric can be varied by means of set-screws, as is evident from the cut; 

 and this must be regulated so that the amplitude of the correction 

 equals that of the periodic error. 



DESCRIPTIVE DRAWINGS OF DIVIDING ENGINE No. 3 



At the end of this article are five cuts of dividing engine No. 3, drawn 

 to scale, one quarter of the actual size, showing different views and 

 operations. They may be described as follows: 



Fig. 1. Side elevation, showing the engine in a ruling position. 



Fig. 2. Plan view of the foregoing. 



Fig. 3. Plan view, showing the plate-carriage. The plate, plate- 

 holder and ruling-head are omitted. 



Fig. 4. Side elevation opposite to Fig. 1, showing the engine in 

 the return stroke position. 



Fig. 5. Transverse sectional elevation, showing the feed-screw, nut, 

 etc. The mechanism actuating the corrector-frame is shown as an 

 end-view. 



