MANUFACTURE OF PLASTERS. 



35 



nipper, weighing 8100 Ibs. and with a 36"X12" belt pulley, is quoted 

 as having a capacity of 10 to 14 tons per hour, and is listed at $550. 



The "nipper'' is usually followed by the "cracker" (Fig. 6), which 

 is a heavy machine of the familiar toothed spindle type. A cracker 





FlG. 6. Cracker for intermediate reduction. (Butterworth & Lowe.) 



weighing 8000 Ibs. has a capacity of 12 to 15 tons per hour, and is listed 

 at $850. 



For the final reduction the Stedman disintegrator, Sturtevant rock- 

 emery mill, or ordinary buhrstones are generally used. The last two 

 machines are described in a later section of this volume (pp. 239, 240), as 

 they are quite extensively used in grinding natural-cement clinker. 



