Portable boring machine

A boring head for a boring bar assembly, the assembly including a rotatably drivable boring bar extending along an axis, the head comprising:

• a body supportable on and for rotation with the bar;
• a tool holder operable to support a tool to work on a workpiece, the holder being supported for radial movement on the body to adjust a radial position of the tool relative to the axis;
• a carrier selectively connected to the holder in a first radial position, in which the tool is a first radial distance from the axis, and in a second radial position, in which the tool is a second radial distance from the axis;
• and
• a radial adjustment screw connected between the body and the carrier, the screw being rotatable to adjust the radial position of the tool relative to the body.

A boring bar assembly comprising:

• a rotatably drivable boring bar extending along an axis;
• and
• a boring head including
• a body supportable on and for rotation with the bar, the body defining an opening for receiving the bar,
• a first tool holder operable to support a first tool on a first radial side of the bar to work on a workpiece, the first tool holder being supported for radial movement on the body to adjust a radial position of the first tool relative to the axis, and
• a second tool holder operable to support a second tool on a second radial side of the bar to work on the workpiece, the second tool holder being supported for radial movement on the body to adjust a radial position of the second tool relative to the axis;
• wherein the first tool holder and the second tool holder are radially movable along a radial adjustment axis between a radially-inward nested position, in which at least a portion the first tool holder nests in the second tool holder, and a radially-outward position in which the first tool holder and the second tool holder do not nest;
• wherein the axis and the radial adjustment axis lie in a plane;
• and
• wherein the first tool holder includes a first portion on one side of the plane and a second portion on an opposite side of the plane and the second tool holder includes a third portion on the one side of the plane and a fourth portion on the opposite side of the plane, the second portion nesting in a recess in the second tool holder between the third portion and the fourth portion, the third portion nesting in a recess in the first tool holder between the first portion and the second portion.