Monday, May 08, 2006

Hydraulic workholding

The basic workholding accessory for a wood or metal turning lathe is faceplate. It is a circular metal plate which fixes to the end of the lathe spindle. The workpiece is then hold tightly to the faceplate using t-nuts in the faceplate slots. It may be attached to the lathe using thread and a precision cone arrangement. Camlock arrangement is commonly used where shaped studs and cams replace threaded studs for rapid exchganging of the faceplate with other accessories, such as three or four jaw chucks. The different types of workholdings are pneumatic workholding, vacuum workholding and hydraulic workholding.

The faceplate was the ancestor of lathe chuck, an arrangement of three or more adjustable 'dogs' bolted to the faceplate providing a primitive chuck arrangement. It may seem that the faceplate is a primitive accessory superseded by precision chucks, but its inherent flexibility and the possibility of achieving great accuracy by careful setting up mak it an essentail for the well equipped lathe.

For certain specialist jobs temporary or special faceplates can be made, perhaps in wood or light alloy that can be machined or adapted for difficult workholding jobs. One example might be attaching thin sheet metal to a wooden face plate using woodscrews, allowing the trepanning of holes, with the tool cutting into the sacrificial faceplate material.