Counterboring seat ring bores

VD4HD-ADM Counterboring Machine


The VD4HD-ADM is designed to to counterbore the valve seat ring bore for oversize seat ring installation.

Working Principle:

The counterbore is machined to the preset depth by the simultaneous application of both a rotary and vertical or horizontal feed motion to the carbide cutting insert.
While the cutting insert rotates in a circle around the counterbore, a feed gear mechanism ensures a continuous feed motion.
The lathe-type refacing action provides smooth and closely fitting contact surfaces for oversize valve seat rings.


The motor drive unit of the VD4HD-ADM is identical with the motor drive unit of the VD4HD Valve Seat Refacing Machine and, therefore, is only required, if no VD4HD is at hand. Two types of exchangeable boring gear heads are available.
The standard AV boring head is provided with a vertical slide for counterboring. The optional AVH boring and facing head is provided with a vertical and a horizontal slide for counterboring and facing the bottom of the bore. The precision boring tools are equipped with a micrometer dial for adjusting the cutting diameter of the cutting insert to ensure high precision machining to IT6 tolerances. Form boring tools are available for machining shoulders within the counterbores under special angles to facilitate O-ring installation. The pilot used for valve seat refacing can be also used for centering the VD4HD-ADM. The boring head can be replaced by a seat refacing gear head to convert the VD4HD-ADM to an VD4HD valve seat refacing machine.

The economical solution for both on site and workshop use.


Boring diameter range min. Ø66 - max. 225 mm
Feed motions:  
Speed range 100 - 250 rpm
Feed range 0,05 mm/rev
Length 410 mm
Width 145 mm
Height 400 mm
Net weight approx. 20 kg


Setup is fast and easy.
Place reference disk on boring tool setting stand to set micrometer screw to a reference value near desired diameter. Place machine on boring tool setting stand and preset boring diameter. Lock the pilot with mounted supporting spider in the valve guide. Then, lower the machine over the pilot and position the cutting tool in front of the upper edge of the seat ring bore. Refacing is automatic. Pressing one button is enough to start the boring pass. Two to three passes will be required to counterbore to the desired diameter.

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