Makita DBM131 Manuel D'instruction page 43

2.6 Core can be removed from the core-bit by tapping or pressing it out from behind.
Never hit the core-bit itself with a hammer, as this can damage it.
2.7 Remove blind core (no through bore) by the aid of cold chisel or similar, levering it loose
against groove wall.
2.8 At overhead drilling always use water collecting equipment so to prevent water entering
the machine. Do not attempt to protect the machine by covering as this inhibits motor
cooling and would cause burn-out by overheating.
2.9 Water collecting rings are available for all drill bit sizes. The ring is secured to the
central screw or the centering tip of the stand base. Cut the rubber gasket about 3mm
bigger than the core-bit diameter.
2.10 Always remove broken off core-bit segment(s) from the cut groove before re-
commencing any further drilling.
3. Core-Bit
3.1 Use only core-bits recommended by your local specialist supplier or manufacturer's
agent. Follow their advice for particular application. There is no such thing as one/or
universal core-bit that can satisfactorily drill concrete, reinforced concrete, granite,
marble and (asphalt/tarmac).
3.2 A high content of rebar or very hard ballast in concrete will cause quicker blunting of
core-bit. Re-dress more often by cutting into piece of corundum grinding wheel to re-
expose diamond particles.
3.3 There is proportionate relationship between hardness of diamonds impregnated
segment material, cutting speed and abrasiveness of material being cut. Follow speed
instructions of the drilling machine. The optimum cutting speed is between 2 and 5
m/s.
3.4 Should core-bit jam or there is no progress made when drilling, check to ensure that
there is sufficient amount of diamonds present in the surface of segments. If this is not
the case, replace the core-bit.
4. Safety Switch
4.1 Check RCD (Residual Current Device) daily, following enclosed instructions. Make
sure to use it as for any submerged pump or similar where RCD or FI-Box are a must.