Grinder tightens up barstock tolerances

Grinder tightens up barstock tolerances

While the market for precision-ground barstock grows, suppliers are often hampered in their abilities to consistently produce the material at required tolerances.

The automated infeed table on the Viking at Bohler-Uddeholm loads and feeds raw barstock and supports each bar as it passes through the high-precision grinder.


While the market for precision-ground barstock grows, suppliers are often hampered in their abilities to consistently produce the material at required tolerances. This is why Böhler-Uddeholm, a South Boston, Va., supplier of highspeed steels and powder-metallurgy-produced tool steels upgraded its centerless-grinding operations.

The company's four older Cincinnati grinders easily met the industry-standard tolerances of ±0.001 to 0.002 in. on diameter for high-speed tool steel in sizes from 0.125 to 0.750 in. in diameter, but they had trouble with precision-ground bars. So, Böhler-Uddeholm added a Landis Grinding Systems, Waynesboro, Pa., Landis Cincinnati Viking Super Series centerless grinder to its in-house grinding operations. The Viking holds barstock-diameter tolerances as tight as +0.0003/–0.0002 in. on 10 to 12-ft bars and handles the shop's bar-diameter range from 0.1 up to 1.125 in. With a through-feed grinding cycle, it automatically grinds barstock and includes an automatic bar loading and unloading system. This automation, which features infeed and outfeed tables, supports and feeds bars as they are ground.

According to Trevor Biggs, manufacturing manager at Böhler-Uddeholm, the Viking quickly compensates for maintaining precise tolerances on long parts through a virtually continuous process. Landis engineers attribute this to the machine's submicron control resolution, 2.5-in.-diameter ballscrew, dual-axis slide drives, linear-scale feedback and AC brushless servomotors combined with a rigid, nodular cast iron and epoxy-granite base that delivers 3,000 pounds per inch of static stiffness.

The grinder's two wheels incorporate Twin-Grip mounting that eliminates orbiting and resists wheelseparating pressures under heavy loads, an arrangement that provides maximum rigidity between the spindles for consistent part geometry.

An easy-to-use, PC-based machine control speeds and simplifies setups and operation, while dual processors let Böhler-Uddeholm create and edit programs and use third-party software for SPC or other managementreporting programs while the machine cycles.

With the Viking's 18-in.-diameter, 10-in-wide grinding wheels, the shop gets 30% more square inches of abrasive to reduce stock removal per revolution of the part and increase grinding-wheel life. landisgardner.com

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