New Engine for Ruling. 67 



.a centrally situated steel ring carrying reversible suspension hooks 

 .and two projecting arms which bear against polished steel rods 

 •extending from platform to floor, and serving as guides to direct 

 and steady the nut in its ascent or descent, and also prevent its 

 rotation. As will be seen, the grinding nut is counterpoised by 

 weights; the pulleys and cords travelling with a minimum of fric- 

 tion. The rotary motion of the screw was made variable, ranging 

 from 120 down to 40 revolutions per minute, the latter being the 

 •slowest rate of speed used. It is hardly necessary to state the 

 fitting up of these simple appliances was carried out with care, the 

 rotation of the spindle, particularly, being made as true as pos- 

 sible, and if-ee from vibration or shock, especially at the moment 

 of reversal, which was always made with a reduction in speed. 



(v.). — Mode of operafi/iff fhe Mechanical Grinder.- — In operation, 

 'the mechanical device just descril^ed presented no great difficulty. 

 Once the screw had been adjusted to run smoothly, the nut was 

 screwed into position, the clamjis meanwhile being released, and 

 oil, without any abrasive, applied as a lubricant, and the machine 

 was ready for a trial run. In order to avoid the possibility of 

 seizure between screw and nut, the latter was controlled by hand 

 for a time, the projecting sleeves being withdrawn from the central 

 ring, leaving the screw free to revolve while the machine was being 

 stopped. These precautions were no longer necessary once the 

 machine was found to run smoothly, and some experience of its 

 working had been gained. It will be understood that grinding with 

 a power-driven machine differs materially from the same work con- 

 trolled by hand, and is to a greater extent dependent upon the sense 

 of touch and hearing; these l>eing the chief means of estimating 

 and controlling the nature and extent of the woi-k being done. 



The mode of applying abrasive is now of considerable import- 

 ance, and can be controlled and varied so as to materially modify 

 its effect upon the screw. Ordinarily, when applying a fresh grade 

 of abrasive or re-commencing operations after cleaning nut and 

 screw, it was usual to release all clamping pressure and run off the 

 nut below the screw; the latter was then coated with a thin even 

 film or layer of abrasive mixed with oil — and in this connection 

 it may be remarked that a light mineral oil and olive oil in equal 

 parts, was later used. This combination was found to possess cei - 

 tain advantages over either of its components used alone. Thin 

 mineral oil was found to dry up rather rapidly and was more liable 

 lo produce an increase of temperature in consequence, while olive 



