338 Mr Whitelaw^s Desaiption of 



work, and it does it as well as any self-acting lathe ; besides, 

 when the iron is hard, which is frequently the case in thin 

 pulleys, a lathe is good for nothing, and this makes no diffe- 

 rence in a grinding machine : a grinding machine will finish 

 pulleys cast much thinner than any that can be turned ; this 

 is a saving of metal : from the manner in which the ends of a 

 pulley work past the sides of the stone, it always keeps in good 

 order : all these are advantages which a grinding machine has 

 over a lathe, in finishing pulleys or drums. 



As the crank is made forked, and as the part o o has a groove 

 in it open at both ends, for the bush of the crank-pin to work 

 into, the crank-pin can easily be taken away by unscrewing the 

 nut which holds it to the crank, and then the spindle dd will 

 not be wrought endways by the motion of the crank. When 

 the ends of a pulley are to be ground, the crank-pin is taken 

 away and a pincing screw is fixed upon the rod r r, which acts 

 upon the part o o, so as to press the spindle d d on end, the 

 one way or the other, as required ; then if the pulley is shifted 

 past the side of the stone, the pincing screw will press its end 

 against the stone, and, if the machine is kept in motion, the 

 end of the pulley will be ground. Having the crank forked 

 answers another purpose ; it allows the pin to be shifted further 

 from, or nearer to, the centre of its shaft, in order to give a 

 longer or shorter range to the motions which the crank gives 

 to the spindle and mandril. A machine for grinding drums 

 should be made wider than the one shewn in the sketch, at the 

 place where the stone and the pulley to be ground work, in 

 order to get the ends of a long (Jrum ground, when they are 

 not finished in the turning lathe, at the time the drum is chuck- 

 ed, to get its eye bored out. Perhaps the simplest way of fi- 

 nishing the ends of a pulley which is bored out in the eye, is 

 to do it in the lathe when it is on the chuck. When a pulley 

 is finished, and it is to be taken out of the machine, or when 

 a rough pulley is to be put into the machine, the cutter t is 

 driven out, and then the mandril cc is drawn on end by 

 means of the handle w, after the key which holds the pulley 

 upon the mandril is slackened. Any of the plummet-blocks 

 which guide the spindle d d and mandril c c can readily be taken 

 away, and a larger or smaller one put in its place; by this 



