The GH-Z/E tool system allows automatic front and back or only back spotfacing and countersinking in large dimensions with high process reliability. The blades are radially retracted into or extended from the blade housing by the right-hand and left-hand rotation of the spindle. This requires a torque bracket which prevents rotation of the GH-Z/E tool by means of a stop lock on the machine. The torques produced are very low and do not stress either the GH-Z/E tool system or the machine.

The extremely rugged and stable design of the GH-Z/E tool allows the manufacturing of screw head countersinks or spotfacings at the back of large work pieces with large bores. Aluminium, grey cast iron, steel or Inconel can easily be machined even with interrupted cuts.

The GH-Z/E tool system allows bore diameters (d) from about 20 mm to about 80 mm to be processed. The maximum countersink diameter (D) is typically 2xd-2. Larger dimensions are also possible, depending on the specific application. Typical applications include screw head countersinks on housings and components of turbines, wind power stations, gearings, pumps, aircraft and large flange elements. Other applications include spotfacings on planetary gear trains and bearing elements, e.g. for earthmoving equipment, railway and aircraft components. Each GH-Z/E tool is optimally specified to suit the particular application and the material to be processed.

Countersinking is carried out from the same side as previous boring. On the basis of a change in the direction of rotation of the spindle, the blades are automatically radially retracted into or extended from the blade housing. The blades are retracted with left-hand rotation of the spindle. They are extended with right-hand rotation of the spindle.

Two bolts which are eccentrically positioned in the blade control engage in a groove in the two blades. As soon as the blade control starts rotating, the blades – which are held in the blade housing so that they can move – are radially retracted or extended. The blade control is connected to the shank and is thus directly driven by the spindle. A driver system inside the control housing allows relative rotation of approx. 180° between the blade control and the blade housing. A torque bracket prevents rotation of the control housing.

When the spindle is started for right-hand rotation, the blade control will first rotate and cause the blades to be extended. As soon as the blades have been completely extended, the spindle RPM are transmitted to the blade housing. The blade housing and the blades now start a right-hand rotation with the spindle RPM and are ready for machining. When the spindle is switched to left-hand rotation, the reverse process is initiated. The blades and blade housing stop. The blade control performs a left-hand rotation and controls the two blades. As soon as the blades have been completely retracted into the blade housing, the spindle RPM are again transmitted to the blade housing. The blade housing and the blades now perform a left-hand rotation.

1. Anti rotation device
2. Shank
3. Tool head
4. Blade housing
5. Blade control
6. Blade/cartridge with insert

The GH-Z/E tool head is available in three design versions. The selection of the tool head is essentially determined by the bore diameter. Each tool is individually specified and produced for each particular application. The chart shows the standard application ranges. They may be extended to cover additional applications.