Multi-spindle unit

A multi-spindle unit for holding a plurality of rotary cutting tools, which is attachable to a first spindle of a machine tool, comprising:

• a unit body removably fixed to the first spindle for rotation thereof about an axis of the first spindle;
• a rotatable shaft axially and radially displaceable relative to said unit body, and coupled at one end portion thereof to said unit body for receiving torque from said unit body;
• a positioning member fixedly disposed radially outwardly of said first spindle;
• a casing disposed radially outwardly of said rotatable shaft such that said casing and said rotatable shaft are rotatable relative to each other, said casing being engageable with said positioning member for accurate alignment of a centerline of said casing with said first spindle and for accurate circumferential positioning thereof about said centerline when said unit body is fixed to said first spindle;
• biasing means for holding said casing in pressed engagement with said positioning member after said unit body has been fixed in place in said first spindle;
• a plurality of secondary spindles disposed in said casing at a plurality of locations radially spaced from an axis of said rotatable shaft, each secondary spindle being rotatable about an axis thereof parallel to said axis of the rotatable shaft and having a tool mounting portion at a free end portion thereof which protrudes from said casing to rotatably support a cutting tool;
• and
• a rotation transmission mechanism disposed within said casing for transmitting rotary movement of said rotatable shaft to said secondary spindles.

A multi-spindle unit for holding a plurality of rotary cutting tools, which is attachable to a first spindle of a machine tool, comprising:

• a unit body removably fixed to the first spindle for rotation thereof about an axis of the first spindle, said unit body having a bore formed centrally therein;
• a torque member removably fixed in said bore of said unit body for rotation therewith, said torque member having a through-hole formed centrally therein with a key slot formed in an inner circumferential surface of said through-hole;
• a rotatable shaft axially and radially displaceable relative to said unit body, having a diameter less than a diameter of said through-hole of said torque member at one end portion thereof, and further having a key extending radially from said one end portion engageable with said key slot of said torque member, thereby to couple said rotatable shaft to said unit body through said torque member for receiving torque from said unit body;
• a positioning member fixedly disposed radially outwardly of said first spindle;
• a casing disposed radially outwardly of said rotatable shaft such that said casing and said rotatable shaft are rotatable relative to each other, said casing being engageable with said positioning member for accurate alignment of a centerline of said casing with said first spindle and for accurate circumferential positioning thereof about said centerline when said unit body is fixed to said first spindle;
• a plurality of secondary spindles rotatably disposed in said casing at a plurality of locations radially spaced from an axis of said rotatable shaft, each secondary spindle being rotatable about an axis thereof parallel to said axis of the rotatable shaft and having a tool mounting portion at a free end portion thereof which protrudes from said casing to rotatably support a cutting tool;
• and
• a rotation transmission mechanism disposed within said casing for transmitting rotary movement of said rotatable shaft to said secondary spindles.