Handheld Core Drills

A core bit that jams stops in a fraction of a second, and the whole motor torque then passes into the housing — and into the operator's arms. The larger the diameter, the longer the lever on that force, so the hand-held limit comes from geometry rather than from machine weight.

Hence two different figures in the data. The DD 18 and DDB 26 drill to 80 mm by hand and to 200 mm on a stand — the same machine, the same motor, two and a half times the range. Going past that limit "just for a moment" is the commonest cause of wrist injury with this class of tool.

The second safeguard is an overload clutch: when the bit binds it disconnects the drive before the torque can wrench the machine away. It does not replace a sound working position, though — both hands on the grips, a stable stance, never at arm's length off a ladder.

The "max diameter" row refers to work on a stand; by hand the limit is 80 mm whatever the rating. The DB 16 data sheet gives a single figure without that distinction, which is why the hand-held row shows "—" rather than a number no source confirms.

All four machines carry an external 1¼" UNC thread (7 threads per inch) and a G 1/4" water connection, so bits and fittings interchange between them. The DD 18, DDB 26 and DDB 26P also run on 110 V, which matters on sites where reduced-voltage supply is the rule.

The peripheral speed of a core bit has to stay in the band where diamond abrades instead of glazing. Because peripheral speed rises with diameter, the bigger the bit, the lower the rpm — which is what the gearbox is for.

On the DD 18 and DDB 26, three gears (580–2800 and 620–2680 rpm) cover everything from small service bits to ⌀ 200 mm on a stand. Top gear serves diameters of a few tens of millimetres, bottom gear those above a hundred.

The DDB 26P has one gear at 840 rpm, and that is not a simplification but a consequence of the micro-impact: a percussion mechanism works within a narrow speed band, and the machine is intended for the diameters where that band is right.

A brushless motor on the DDB 26 and DDB 26P has no carbon brushes — the part that wears first in this class and sets the first service interval. Efficiency shows too: these machines weigh 7.1 kg at 2600 W, while the brushed DD 18 weighs 8 kg at 1800 W.

Mechanical micro-impact adds small axial blows to the rotation. It is unnecessary in clean concrete, but in masonry, hollow block and non-uniform material it breaks what abrasion alone will not take — the bit stops stalling on a hard inclusion. The DB 16 and DDB 26P have it.

The 36 and 48 mm extraction ports on the DDB 26P allow dry drilling with dust captured at source. That is the only way to work where water is unacceptable — above electrical installations, in a finished room, on a slab over an occupied floor. Extractors for it are in industrial vacuum cleaners.

Start from diameter, but read both figures

The quoted maximum applies on a stand; by hand the limit is 80 mm. If ⌀ 100–160 mm penetrations come up regularly, the answer is not "a more powerful machine" but "machine plus stand" — and then it is worth looking straight at complete core drill rigs.

Establish what you are drilling

In clean concrete and reinforced concrete, power and bit selection decide. In masonry, clay block and material with hard inclusions, micro-impact wins, because the bit does not stall on an obstruction. That is why the DB 16 and DDB 26P are machines for service penetrations in buildings rather than for industrial floors.

Work out current and voltage

9 A on the DD 18 and 12 A on the 2600 W machines fit a 16 A circuit, but sharing an extension lead with a vacuum removes the margin. If the site runs on 110 V, three of the four machines will work on it — the DB 16 is listed for 230 V only.

Decide between water and extraction

Wet drilling cools the bit and flushes the swarf, but leaves slurry that must not go into the drains. Dry drilling with extraction is cleaner and the only option above electrical installations or inside finished rooms — but it needs a machine with an extraction port, which here means the DDB 26P.

Above 80 mm the work moves to complete core drill rigs, and the supporting structures themselves are in core drill stands. Bits for concrete, reinforced concrete and percussion work are in diamond core drill bits. When and how to drill is covered by the parent category, core drills.