How should finished-size tolerance be defined when buying a commercial dicing machine?

When buying a commercial dicing machine, start by fixing the target cube dimensions and their tolerance, then calculate average size, range and out-of-tolerance percentage from continuous samples. Have the supplier run representative material and log the process data, capturing both average performance and abnormal samples, since a good average can hide unstable operation. Link each requirement to a measured result rather than marking it passed. Where several models look alike, compare measured application data instead of motor power or nominal speed.