a modular material processing apparatus comprises a housing including a frame , the frame defining a pair of oppositely facing lateral ends and a pair of oppositely facing longitudinal sides ; a pair of co - acting , substantially parallel , counter - rotating roller assemblies , each of the roller assemblies including a substantially cylindrical , material processing roller member mounted to a rotating shaft extending substantially parallel with the longitudinal sides ; a first support assembly mounted to one of the lateral ends of the frame , the first support assembly including a fixed support and an adjustable support , each of the fixed and adjustable supports supporting a corresponding one of the roller assemblies ; and a second support assembly mounted to the other one of the lateral ends of the frame , the second support assembly including a fixed support and an adjustable support , each of the fixed and adjustable supports supporting a corresponding one of the roller assemblies . each of the first and second support assemblies include a fixed support block retaining the fixed support ; an adjustable support block retaining the adjustable support and being laterally slidable with respect to the fixed support block ; a shim positioned on a lateral side of the adjustable support block , between the adjustable support block and a fixed member of the support assembly ; and a lock for securing the adjustable support block and shim to the fixed member during normal operation of the material processing apparatus . accordingly , the lateral distance between the fixed support and the lateral support on each of the first and second support assemblies may be adjusted by changing the thickness of the shim .