Chipping In Retaining Pin Slot; Deformation Of The Retaining Pin Slot Sides - NPK PH1 Operator's Manual

TOOL BREAKAGE
A. CHIPPING IN RETAINING PIN SLOT
The tool may become chipped at the upper end of the retaining pin slot where it
contacts the retaining pin. Free standing oversize rock may sometimes be broken with
only a few hammer blows. If the operator does not stop hammering immediately, the
tool will hit the retaining pin (blank hammering), and can chip the upper end of the
retaining pin slot.
PREVENTATIVE MEASURES
When the material is broken, stop operating the hammer immediately. Periodically
check the tool and grind smooth any chipped areas to prevent stress cracks.
B. DEFORMATION OF THE RETAINING PIN SLOT SIDES
The tool may become chipped or deformed in the area where it is in contact with the
retaining pin. As the tool breaks material, it will try to follow any fracture lines in the
material (Fig. 1). This causes a chisel point tool to twist in the tool holder. The retaining
pin limits how far the tool can twist. If this happens often enough, the pin contact area
of the tool can become chipped (Fig. 2) or deformed (Fig. 3).
Fig. 1
PREVENTATIVE MEASURES
The operator should place the chisel point in line with fractures or laminations in the
material, not at an angle. The tool should be checked periodically for chipped areas.
Grind smooth any chipped areas to prevent stress cracks in the tool.
- 41 -
Fig. 2
Fig. 3