an Improved Grinding Machine, 337 



the whole of its length, so as to slide through the shaft I easily. 

 There is a feather fixed into the shaft /, which fits the groove 

 planed into the shaft m w, so that this shaft can slide through 

 the shaft / ; but it cannot revolve unless the shaft / carry it 

 round. Upon the end of the shaft mmo. small crank n is fixed ; 

 as this crank has a perpendicular position in the Figs, it is not 

 so distinctly seen. The crank pin has a brass on it, which slides 

 into a groove running in a perpendicular direction in the part oc- 

 As two sets of the bushes in the part oo work upon journals 

 cut into the spindle d d, if the grindstone revolve, the spindle 

 dd and the mandril cc will work endways, at one time in one 

 direction, then in another, so as to bring an end of the pulley 

 b b past a side of the stone, once for every half revolution of the 

 crank shaft ; and, in this way, the pulley and the stone, as they 

 wear, keep perfectly cylindrical. It will be evident that the 

 mandril and the spindle have no ruffs, and they are turned pii- 

 rallel at the parts which slide and revolve into the plummet- 

 blocks. The bracket pp^ which supports the crank-shaft, is fixed 

 upon the two plummet-blocks for the spindle dd, and, on this ac- 

 count, if they are moved from or towards the grindstone, it is 

 carried along with them. The pulley q, which drives the 

 spindle dd, is connected to it (the spindle) in a similar way as the 

 shaft m m is connected to the shaft /, and the part of the 

 bracket /?/>, seen in the ground-plan passing nearly round this 

 pulley, keeps it always at its proper place. The small rod re- 

 serves to guide the part o o, and keep its groove always in a 

 perpendicular direction. S is the pulley which drives the grind- 

 stone. 



The machine now described grinds fifteen pulleys of 18 inches 

 diameter by 5 inches broad, in a day, working ten hours ; now 

 this is a great quantity of work, considering the very moderate 

 speed at which the parts are driven. When a pulley is finished, 

 if a planed malleable iron straightedge is applied on the rim 

 parallel to its axis, it touches the pulley in every part. After 

 a pulley is ground, it is shifted back from the stone and still 

 kept revolving, then a stick with a little emery and oil on it is 

 pressed against the pulley, and this gives it a fine polish. A 

 grindstone for finishing pulleys is not anything like so ex- 

 pensive to make as a turning lathe : it does incomparably more 



