Niles-Simmons Ni 350

The Niles-Simmons Ni 350 is a CNC internal cylindrical grinding machine built for precision bore grinding of large workpieces — a specialty that distinguishes it from the majority of internal grinding machines that target small to medium bore diameters. The Ni 350 addresses bore diameters up to 350 mm (and grinding depths scaled to the bore diameter), covering large bearing housings, gear blanks, heavy flanges, spindle housings, hydraulic cylinder bores, and industrial ring components found in aerospace, energy, and heavy equipment manufacturing.

Internal grinding of large bores presents specific engineering challenges: the grinding spindle must extend deep into the bore while maintaining stiffness to avoid spindle deflection under grinding forces, thermal growth of the spindle and workpiece must be managed to hold tight bore tolerances, and the grinding wheel must be large enough relative to bore diameter to achieve good surface contact and efficient material removal. Niles-Simmons' Ni 350 addresses these challenges through a robust internal grinding spindle with high-stiffness bearing design, an active thermal compensation system, and an automatic wheel dressing system that maintains wheel form and face geometry throughout the cycle.

The machine grinds cylindrical bores, tapered bores, and combined bore profiles in a single clamping. Face grinding of the workpiece end face is also possible with appropriate spindle orientation, enabling the bore and face relationship to be established in one setup. Workpieces mount on a precision rotary table with C-axis positioning for indexing multi-bore workpieces or for grinding angular bore features.

CNC control is Siemens SINUMERIK 840D sl. Niles-Simmons provides application-specific grinding cycles covering cylindrical bore grinding, tapered bore grinding, plunge grinding, oscillation grinding, and face grinding. In-process gauging with automatic size compensation is standard, allowing the machine to grind to a measured target rather than programmed infeed alone — essential for holding bore tolerances in the IT5-IT6 range that bearing housing applications demand.