Using Your Core Drill

It would be almost impossible to outline all operating and safety procedures to suit all drills on all work sites in all conditions. However, here are a range of factors you need to be aware of when using core drills. These guidelines are not exhaustive. Always use common sense and exercise caution.
If in doubt on any issues, contact your site supervisor, the drill manufacturer, the barrel manufacturer or your local Occupational Health and Safety Commission.

The Essential basics:

• Read safety instructions and operation manual before use
• Wear appropriate personal protection equipment (PPE)
• Core drills and RCD are not waterproof - keep them out of the water
• Do not use the overload protection as on/off switch - the overload will fail
• Do not run off generators, as they may not be 240 volt, 50Hz
• Use only heavy duty (2.5 mm² or thicker) extension cords and keep them as short as possible  (under 15m).
• Use the right speed for the diameter of the barrel (see your manual or here)
• Above 60-70mm diameter, most manufacturers recommend using a stand with your drill.

Selecting Your Core Drill

When selecting a core drill, you will need to know what the largest diameter hole you require to drill,  and will you be drilling by hand or using a stand (drill rig).
Hand held is acceptable for drilling smaller holes or in brick or other soft material, but if drilling larger diameters in concrete or reconstituted limestone, you will require a core drill stand. Generally, drill manufacturers recommend a stand for diameters above 60mm. 

Preparation:

• Read your core drill manual that came with the machine!
• Identify onsite hazards and plan to control the risks they present
• Have a plan of what you are going to drill. Is there any rebar, sewer lines,  electrical lines or gas lines where you will be drilling? Check again you are drilling in the right spot.
• If stressed components or components affecting the integrity of a building are damaged during drilling, operators can be at serious risk
• When coring through floors above ground level, the core will release and fall to the lower level and can cause extremely serious injuries.  Ensure the area below the drill hole is restricted with a barrier and guarded by a worker.
• Ensure you have selected the right sized core barrel that suits the material you are drilling, the type of machine you are using and it's horsepower, and selected the right speed. For operator safety, most manufacturers recommend drilling over 67mm be done with the drill mounted in a stand. If in doubt, contact the barrel or drill manufacturers.
• Check the core barrel for any damage from transport, or from the last time it was used
• Make sure the drill is in correct working order (with all safety guards, RCD etc in place), and will be safely operated by trained users
• Use only heavy duty extension cords, with the biggest copper core diameter. This makes them expensive, but allows electricity to flow better to the drill motor. Use the shortest possible extension lead possible, and never longer than 20 meters due to the ever increasing resistance in current flow.
• Check with the site electrician there is adequate power as the drill may draw up to 25 amps.
• Check all electrical cords and plugs and elevate them to protect them from water. Test the RCD.
• Waterproof grease on the drill spindle thread will make bit changing easier
• Make sure the drill has adequate clean water running before turning on the motor. Otherwise the water jacket seals on the drill can overheat, which will cause them to leak.
• Ensure adequate ventilation is allowed for petrol powered drills like the Golz KB350
• Ensure adequate collection of slurry as per local legislation
• Ensure the user is wearing appropriate personal protective equipment eg hearing protection, safety eye wear, dust mask, gloves, dust/slurry control measures etc. Consider using a PAPR (powered air purifying respirator). For more info on silica, see Safe Work Australia's info here.
• Ensure you have adequate lighting
• Have a fire extinguisher and first aid kit nearby
• Plan for the removal of debris and rubble
• Beware of sun damage to the operator
• You will create silicia dust, even though it maybe in a slurry. See the WA government's info on silica dust here.

Positioning:

• Properly support and clamp the material being cored if necessary e.g. concrete pipe, to prevent movement while working
• Proper rig anchoring is essential to ensure a straight core. The best  method of anchoring the drill rig is using physical anchors rated for core drilling. Providing the surface is smooth and the vacuum gasket is in good working order, a vacuum can also be good option
  
• Many drill rigs also have a ceiling jack that allows the operator to shore the top of the drill stand up to an overhead area with a sturdy piece of wood.
• Ensure the drill collar is fully and squarely seated into the female rig collar, generally tightening both left and right hex head bolts consecutively a little at a time
• When hand drilling, use a guide or template to keep the core barrel in the correct position. A simple template made from wood can be pinned to the concrete wall or stood on when floor drilling. Using your boots as a guide is not recommended.
• An alternative guide to start coring is Core Drill Blocks - see here.
• Make sure there is an exclusion area around the cutting area adequate to keep other workers, general public and animals safe.
• Never work off ladders, crates, drums or chairs. Always use proper access equipment if the work cannot be reached from the ground.
• Be aware concrete and masonry cutting and drilling equipment can be heavy, and the operator may be required to carry it around on site, then hold it in an awkward position for a long time. 
• Use correct manual handling techniques.
• Adopt the correct grip and stance to control the drill. You need to be well balanced as the barrel will turn clockwise to your right and you need to counter the rotational forces.
• Be aware of vibration fatigue and how to manage it.
• Be aware of slippery floors, and unstable or uneven surfaces.
• The risk of harm increases when working alone, even if that is just out of sight of other workers.

Drilling:

• Only start drilling after water starts to flow from the drill bit
• Select the drill speed (R.P.M.) based on the diameter of the core bit. The smaller the diameter then the greater the speed allowable. Refer to the speed chart on "Core Drilling Tips and Troubleshooting" page
• Only change gear when drill is stopped
• Open up the diamonds on a new drill bit with shallow cuts in soft, abrasive material (eg. limestone)
• If drilling by hand, start drilling at a slight angle, then when a crescent shaped notch has formed, raise the drill to the vertical position. Otherwise use a template as guide, a stand or a core drill block.
• Do not force the bit - allow the drill to do the work.  Forcing or twisting the barrel can cause binding, overheating, distortion and segment damage.
• If hand drilling, keep the same drilling angle at all times to avoid uneven wear to the core bit or jamming.
• When removing the bit, turn the water down and back the bit out while the drill motor is still running.
• Check the bit periodically for heat marks, cracks in the steel core or segments, or excessive wear underneath the segment.
• If excessive vibration or 'snatching' at the core barrel is detected – remove the core drill, remove the core and investigate. Remove any loose  material, pieces of steel rod etc. When drilling brick walls,  wall ties maybe encountered -  remove them with pliers. Failure to fix these problems may result in segment damage or loss.
• When the slurry changes colour (usually to gray) or the drill motor speed drops, you are most probably cutting steel. Drop the motor speed down (slowest speed works well) and relax pressure by about 1/3. Raise and lower the drill motor multiple times until you have cored through the steel so the barrel will not bind on the steel. Some operators reduce water after exiting the steel to redress the bit again, but don't forget to turn the water up again afterwards.
• Maintain a straight drilling direction. If you allow the barrel to skew , usually the wall of the barrel will bind in the hole or break off segments.
• If the rate of drilling has slowed, the barrel may have glazed up. Redress the bit by reducing the water by half for a few minutes, or by drilling into an abrasive material like limestone, a cinder block or similar. A bit of Ajax bathroom cleaner or builders sand down the hole can also have the same effect - run the drill at a slower speed, with reduced downwards pressure,  so that an abrasive paste forms that will re-sharpen the segments.
  
• To remove the barrel from the hole, turn the water to very low and remove barrel while drill is still running.
• Never leave a running machine unattended.
• Compared to SDS percussive drilling, drilling with diamonds (an abrasive technology) is the slowest of all cutting methods. You are not drilling a hole, you are grinding it.
  Concrete drilling  with embedded steel can take a long time. Have realistic expectations as to the time it requires.

For a more detailed look at Core Drilling from selecting your core drill to actually drilling  plus all the UDT core drilling supplies; download the guide below.

Download the UDT Core Drilling Guide

These guidelines are not exhaustive. If in doubt, contact the saw manufacturer, the blade manufacturer, site supervisor or local Occupational Health and Safety Commission.

Disclaimer: the information on this website is provided in good faith and believed to be reliable and accurate at this time. However, the information is provided on the basis that the reader will be solely responsible for assessing the information and its veracity and usefulness. UDT shall in no way be liable, in negligence or howsoever, for any loss sustained or incurred by anyone relying on the information, even if such information is or turns out to be wrong, incomplete, out-of-date or misleading.