Lead face machining apparatus

A lead face machining apparatus, comprising:

• a spindle unit adapted to rotatably mount a workpiece thereon, said spindle unit including a spindle, a housing circumferentially disposed around said spindle and a static pressure fluid bearing framed between said spindle and said housing, said static fluid bearing including a bush, a first circumferential passage for introducing fluid under pressure into a space between said housing and said bush, a fluid pocket formed between said spindle and said bush and a radial passage extending between said circumferential first passage and said fluid pocket;
• means for imparting rotary motion to one end of said spindle;
• a plurality of keys formed of an elastic material operably connecting said collar and said spindle;
• an end cam located on an end of said spindle;
• a first horizontal slide table which includes a first pair of guide blocks extending in the same direction as the axial direction of said spindle, said guide blocks having opposing vertical surfaces and coplanar horizontal surfaces and a first table provided slidably along said horizontal and opposing surfaces of said guide blocks, said first table having a first static pressure fluid bearing consisting of a first passage for introducing fluid in a pocket to each of said opposing vertical surfaces and each of said coplanar horizontal surfaces, a plurality of return passages for returning fluid from each of said surfaces to a fluid pressure generating unit so as to constitute a first static pressure fluid bearing between said first table and said guide blocks and additional return passages for returning the fluid to said pressure generating unit spaced further from said first passage than said plurality of return passages;
• a second horizontal slide table which includes a second pair of guide blocks extending substantially at right angles to the axial direction of said spindle unit, said guide blocks having opposing vertical surfaces and coplanar horizontal surfaces and a second table provided slidably along said horizontal and opposing surfaces of said guide blocks, said second table having a second static pressure fluid bearing consisting of a second passage for introducing fluid in a pocket to each of said opposing vertical surfaces and to each of said coplanar horizontal surfaces, a plurality of return passages formed around each of said pockets for returning fluid from each of said surfaces to a fluid pressure generating unit and land portions formed between adjacent pockets and return passages so as to constitute a second static pressure fluid bearing between said second table and said guide blocks and additional return means for returning the fluid to said pressure generating unit spaced further from said second passage than said plurality of return passages, one of said tables being placed on the other of said tables;
• means for moving said first slide table and means for moving said second slide table in a direction substantially perpendicular to the direction of movement of said first slide table;
• a lead machine unit including a cutting tool placed on one of said tables so that it can be brought into contact with said end cam, said cutting tool being caused to slide in the axial direction of said spindle unit upon rotation of said end cam so as to machine a workpiece mounted on said spindle unit;
• fluid supplying means for supplying fluid to said static pressure fluid bearing, said first static pressure fluid bearing and said second static pressure fluid bearing in common;
• and
• means for withdrawing fluid from said additional return passages.