DIVIDING MACHINES. 



ratchet, the effect of which is, that every tenth division made 

 upon the limb by the cutter is distinguished by a longer line than 

 the intermediate divisions. 



In some cases both the motions above described are imparted to- 

 the cutter, the limb upon which the divisions are engraved being- 

 kept at rest. The cutter is, in that case, alternately impressed 

 with two motions, one which transfers it from division to division 

 while it is raised from the limb, and the other in a direction at 

 right angles to this, while it is pressed upon the limb, and makes 

 the incision which marks the division. 



These dividing instruments vary in form and magnitude accord- 

 ing to the purposes to which they are applied. 



Those which are used for engraving the divisions on the circular 

 limbs of theodolites and other instruments of the larger class,, 

 consist of a circular metallic table of solid construction and suit- 

 able magnitude, to which a motion round its centre in its own. 

 plane is imparted by means of a finely-constructed worm, which 

 works in teeth formed on the edge of the circular table itself^ 

 Means are provided by which the circular limb to be divided can 

 be fixed upon this table, so as to be exactly concentric with it, 

 and to be moved with it. The cutter is fixed so as to slide upon 

 a rod which is extended over this table and parallel to it. The 

 cutter can, by this arrangement, be adjusted at any required dis- 

 tance from the centre of the table, so as to correspond to a circular 

 limb of any magnitude not exceeding that of the table. 



In the process of engraving the divisions, the worm and the 

 cutter are moved alternately by self-acting mechanism, deriving 

 its motion from the electro-motive machine by which all the 

 apparatus of the workshop is driven. The worm is so adjusted, 

 that by each action on the table, the limb to be engraved is- 

 moved under the cutter (which is then elevated so as not to act 

 upon it), through a space equal to the interval between the 

 divisions. The worm then stops, and the limb being at rest, the 

 cutter descends upon it, and is drawn through a space equal to- 

 the length of the line to be engraved, and the division is accord- 

 ingly marked upon the limb. The cutter is then again elevated, 

 and the limb again moved under it by the worm, and so on. 



In this case the divisions which mark degrees are distinguished 

 from the intermediate minutes by larger lines, mechanical arrange- 

 ments being provided in the wheelwork by which the motion of 

 the cutter is ,thus affected. 



12. All these machines are self-acting. The limb or scale to be 

 divided being once placed on the table of the dividing engine, no- 

 further interference of the human hand is needed. The machine 

 of itself begins its work at an appointed hour, minute, and 



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