Final answer:
Scallop refers to the height of the material left on a machined surface, indicating the roughness, while stepover is the side-to-side distance between tool paths, influencing the number of passes and surface finish quality.
Step-by-step explanation:
The difference between scallop and stepover is essentially one of path and dimension in relation to machining, specifically in milling or CNC operations. Scallop, also known as cusp height, refers to the height of the leftover material (the 'scallops') after a machining pass and is a measure of surface finish quality. Higher scallop heights usually indicate a rougher finish. Stepover, on the other hand, relates to the side-to-side spacing between passes of a milling tool. A smaller stepover results in more machining passes but can achieve a finer surface finish as the overlaps are closer together, thus potentially reducing the scallop height.