Komatsu PC138US-11 Operation & Maintenance Manual page 434

RECOMMENDED ATTACHMENT OPERATIONS ATTACHMENTS AND OPTIONS
Push the chisel against the impact surface and operate so that
the chassis rises approximately 5 cm off the ground. Do not
raise it off the ground unnecessarily.
When the chisel does not penetrate or break the surface by
continuous impact to the same impact surface for 1 minute,
change the point of impact and perform breaking operations by
scraping from the edge.
Penetrating direction of the chisel gradually deviates from the
direction of the breaker body. Adjust the direction with the
bucket cylinder so that it keeps the proper direction.
Always keep the chisel pressed against the impact surface
properly not to strike at the air.
Prohibited operations
To ensure that the machine has a long life, and to ensure that operations are performed in safety, do not operate
the machine in any of the following ways.
Do not operate all cylinders to the end of their strokes. Always leave approximately 5 cm to spare.
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