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MB156 User Manual ◄ 13
Always direct the down pressure force in a line toward
the point of tool contact with the work.
Moving rocks with the tool bit is another method of bind-
ing the tool bit. This practice should be avoided as it may
cause tool bit failure.
Rebar reinforced concrete introduces the problem of
concrete chunks being held together by the rebar after
the concrete has been broken. The best approach to this
problem is to use a chisel point tool which permits cut-
ting the rebar with the breaker. Another method is to pe-
riodically cut the rebar with an oxy-acetylene torch
BLANK FIRING
To understand “Blank Firing”, the operator needs to be
aware that the tool bit is able to drop down in the lower
body cavity, far enough so that the piston cannot strike it,
when the tool bit is not in contact with the work surface.
“Blank Firing” occurs whenever the breaker is operating
and the piston is not able to strike the tool bit solidly or
not strike the tool bit at all. “Blank Firing” accelerates
wear and tear on breaker and carrier components and
may result in failure of one or more components. Exces-
sive “Blank Firing” may be considered equipment abuse
and may result in voiding warranties.
Break-through or difcult surface contact results in
“Blank Firing” when the material being broken fractures
and the tool bit is no longer in “hard contact” with the
material but is still pushed high enough in the lower body
cavity so that the piston can strike it. In this position, the
piston strikes the tool bit and the tool bit, in turn, is driven
against the retaining pins because it is not in sufcient
contact with the material to be broken. The energy is ab-
sorbed by the retaining pins, other breaker components,
and the carrier boom components. “Blank Firing” of this
type can be experienced in trench work where obtain-
ing striking contact with the work surface is difcult or
the wrong tool bit is used, or in at rock work where the
operator fails to stop operation of the breaker when slip-
page, fracturing or material break-through occurs.
“Blank Firing” as a result of operator error occurs when
the tool bit is not in contact with the work surface to be
broken and is allowed to drop down in the lower body
cavity so that the piston is not able to strike it. Instead,
the downward movement of the piston will be stopped
by an internal oil cushion located at the bottom of the
piston’s stroke and the energy of the piston will be ab-
sorbed by breaker components and excavator boom
components. “Blank Firing” of this type can be experi-
enced when the operator fails to stop operation of the
breaker when the material fractures or material break-
through occurs, or during re-positioning of the breaker.
Scoring with the breaker
Figure 8. Scoring with the Breaker
Breaker tool binding can cause erratic breaker opera-
tion and premature wear on the tool shank. Breaker tool
binding is caused by failure to direct the down force in
the direction of the tool bit.
Breaker tool bit binding
Figure 9. Breaker Tool Bit Binding
CAUTION
Do not pry with bit and breaker. The tool bit may
break causing injury.
Excessive side force cocks the tool in its bore, prevents
proper movement and causes premature tool shank and
bushing wear. Since the breaker tool bit must be pushed
up into the breaker to operate, a binding tool prevents
the breaker from operating correctly. Binding also causes
the tool bit and tool bushings to seize and often results
in breakage of one or more breaker components.
OPERATION