Makita DBM230 Notice Originale page 27

Overhead drilling
You must install a water extracting device.
Connect a wet vacuum to the extracting device and switch it on.
Open the water supply and ensure that the water reaches the
segments before you start drilling.
When drilling overhead take special care that no water enters into the
tool.
In case you notice during drilling that the advance speed becomes very slow,
that you have to employ increased pressure and that the water emerging from
the borehole is clear and mixed with metal splinters you probably have hit
reinforcement iron.
Reduce the pressure on the drill bit and switch to the next lower gear if
possible in order to separate it without problems. You may increase the
pressure, and the drill speed after separating the reinforcement.
Extension of the drill bit
If you have to drill deeper than the working length of the drill bit permits:
At the outset, drill only as deep as the working length of the bit permits.
Remove the drill bit and take the drill core out of the drilled hole
without moving the core drilling installation.
Replace the drill bit into the drilled hole.
Install an appropriate extension between drill bit and motor. If the drill bit
holding fixture is 1¼ " do not forget to install the copper rings in order to
facilitate the loosening of the drill bit.