Pratt Burnerd International (www.pratt-burnerd.co.uk) has launched a new range of high accuracy big centers, available for both manual and CNC machines, suitable for the oil and energy industries. The centers can also be used for any application where large components need to be accurately turned, ground or bored.
The new centers have been engineered for accuracy and durability, offering a workpiece capability of up to 180,000 kg (482,263 lb).
Perpendicularity, absolutely critical in a live center, is 0.0025 mm perpendicular to the centerline of the taper shank. This conforms to the strictest of DIN standards and ensures maximum rigidity in operation.
The spindle is supported by multiple bearings to spread the load over the full length of the taper. Bearing bores are ground concentric and coaxial to the taper in one operation to ± 0.0025 mm (0.0000984 in) for maximum accuracy and bearing life.
The full length of the spindle maintains maximum rigidity and dampens vibration through precisely calculated fulcrum positioning. This also ensures that it will flex rather than break when subject to severe loads. The design of the gaugeline cross section, combined with the robust spindle construction, provides good resistance to deflection. The threaded seal adapter/ retainer is lapped to be parallel to the bearing face to ensure consistent accuracy and rigidity. Points are hard-turned to 61 to 63 HRc and bodies are heat treated for extra strength.
Both live and dead centers are available with accuracies of to 0.005 mm. The range includes centers rated up to 12,000 rpm, ideal for hard turning applications. Heavy-duty centers, for exceptionally heavy workpieces, are of a fourbearing design to ensure radial pressure, thrust and rigidity requirements. Knockout ends on carbide tipped dead centers are hardened to reduce wear and friction.