Machine for Drilling AC Holes in Concrete

If you are an AC technician or contractor running AC pipes through concrete walls or ceilings, breaking the wall with a hammer and chisel damages the area around the hole and wastes your time. A core drilling machine makes a clean, round hole at the exact size, with no breaking.

See machine and bit prices

The right machine for AC holes in concrete

• Occasional holes and light work: the Oubao 160 handheld core drill. It drills concrete up to 5 inches at 20 cm depth, weighs 7.4 kg and works without a stand. To be honest with you: the Oubao 160 is powerful and violent. If the bit jams it does not stop instantly and can kick back hard in the operator's hands, which can cause accidents or injuries, so it needs a trained operator.
• Many holes every day, or heavy reinforced concrete: the Oubao 8 inch core drill on its stand. The stand keeps the machine steady, so the hole is faster and more accurate, and it runs every bit size up to 8 inches.
• Not sure? Work it out yourself in under a minute using the hole diameter, depth and holes per day.

The machine comes on its own without bits. You buy only the bit size your job needs.

What bit size do you need for an AC hole?

AC unit	Suitable bit size
1 or 1.5 HP	2.5 inch (63 mm)
Most units from 2.25 to 5 HP	3 inch (76 mm)
Larger units or more pipe runs	3.5 inch (83 mm)
More than one pipe run through the same hole	4 inch (102 mm)

The safest way: measure the insulated pipes, power cable and drain hose together, then choose a size slightly bigger so they pass easily. If the AC manual states a size, follow it.

Note: an inch in core drilling is 25.4 mm, which is different from a plumbing inch.

How to drill an AC hole in concrete, step by step

1. Mark the spot: stay away from columns and beams, and make sure no water pipes or power cables run along the path.
2. Angle the hole slightly downward to the outside: about 3 to 5 degrees, so the condensate drains outside and does not run back into the room.
3. Fit the right bit: pick the size from the table above.
4. Connect water for cooling: water is what keeps the bit alive. If there is no water source nearby, use a water pump.
5. Start slowly: wait until the bit settles in its path, then increase the pressure gradually without forcing it.
6. If the bit suddenly stops: on a stand machine, the safety clutch disconnects the drive because the stand is anchored, so pull back a little and continue. A handheld machine does not stop instantly and can kick back hard in your hands, so light pressure from the start matters most.
7. When you finish: remove the core (the piece of concrete that was cut), clean the hole, pass the pipes, power cable and drain hose through, and seal around them well.

Important warning: do not drill through a main column or beam without asking a structural engineer first, because cutting the reinforcing steel in those places can weaken the building.

The machine pays for itself quickly

Every hole you pay someone else for is a hole your own machine can do every day. Work out how many holes pay for the machine.

• Learn quickly: you get the free core drilling video course, from opening the box to drilling on your own.
• Your work never stops: if the machine breaks down within a year of purchase, you get a free replacement machine until the repair is finished.
• The bit is not thrown away: when the segments wear out, re-tipping brings the bit back to work – and the fitting includes 3 tests on the bit (wall thickness, runout and ovality) plus trimming it, to make sure it is fit to work again.