Portable model mounts directly onto framework of calender equipment to let users grind rolls in their own bearings without hand or block grinding. Eliminating need to remove rolls, self-reversing, traversing grinder can redress calender rolls in-place up to 240 in. long. It can achieve tolerances to 0.0005 in. on dia, concentricity, and straightness, with finishes as fine as 12 rms, depending on grit of grinding medium.