The company has engineered “force control” into 16C and 20C step chucks to prevent crushing or distorting thin-wall parts during turning and grinding operations. The concept incorporates a customized spring-loaded design as the primary closing mechanism. The lathe closer will bottom out before the spring system reaches its solid height. The Force-Limiting step chuck can be used to replace a standard power chuck when turning large- or small-diameter, delicate or thin-wall parts.
The chuck assembly adjusts the grip, while reducing the need to manually modify the drawbar force. The actuation of the system is force independent from the machine drawbar. Users can operate at normal pressure, virtually eliminating loss of closing cycle time associated with a low pressure setting, the company says.
Another concern is maintaining OD and ID concentricity. Concentricity is maintained because the proper grip force is predetermined and applied to the process automatically. Weighing less than a power chuck, the Force-Limiting step chuck doesn’t require a hoist to mount it. According to the company, it mounts directly in the spindle with minimal overhang from the spindle bearings, therefore transferring spindle accuracy directly to the workpiece.
These chucks are currently used in the company’s CNC lathes with a drawbar stroke of 1/2" or less and are available in 16C and 20C sizes. Applications include gripping thin-wall tubing, pipe, castings, housings and soft or delicate materials that cannot withstand standard chucking methods.