Diamond Drill Bits
HERMEQ supplies diamond core drill bits for professional diamond core drills, engineered in Germany and manufactured in the UK. The range covers wet and dry diamond drill bits for coring concrete, brick, block and masonry. It also includes shorter wet bits, which civils and utility contractors use for duct entries, chamber connections and kerb work, and small diameter bits for fixings, anchors and service runs.
Wet and dry diamond core bits
Wet coring is the method for reinforced concrete, floor slabs and deep or large diameter holes, and dry coring suits brick, block and lightweight masonry, where water would damage finishes or cannot be controlled. Water cools the segments and flushes slurry out of the cut, so a wet bit keeps its cutting speed through dense aggregate and steel reinforcement and lasts longer in heavy coring.
Dry bits are the choice in occupied buildings, fitted-out interiors and decorated walls, where slurry on floors, finishes or electrics is not acceptable. The dust they produce contains respirable silica, so dry coring is done with an M or H class extractor connected at the drill.
Short and small diameter core drill bits
Short wet core bits for civils and utility work
Short wet core bits suit shallow structural cores where the barrel of a full-length bit is more than the job needs. Typical uses are duct entries into chambers, manhole and inspection chamber connections, and cores through kerbs, slabs and thin concrete walls. A shorter barrel is lighter to handle on a handheld drill or inside a confined chamber, and it reaches full depth with less travel on the rig.
Small diameter diamond drill bits
Small diameter diamond drill bits cut holes too small for a standard core, such as holes for fixings and resin anchors in reinforced concrete, cable runs and small bore pipe entries. They run on the same professional core drills as the larger bits. A fixing hole through rebar or a cable entry through a slab is therefore cut with the same kit, and there is no need to reach for a tile bit or a hammer drill.
Matching a diamond core drill bit to the drill and the hole
With the method settled, the bit still has to fit the drill, clear the service it carries and reach through the structure, and each of these is checked before ordering.
Drill connection and motor
The threaded connection on the bit has to match the spindle of the core drill, or an adaptor made for that spindle. Larger diameters need a motor with the power and low gear speed to drive them. The drill's maximum rated diameter for wet and dry use sets the largest bit it should run.
Diameter for pipes, ducts and services
Core one size above the outside diameter of the pipe, duct or cable bundle. This leaves room for a sleeve, puddle flange, collar or fire-stopping, and for any fall the pipe needs through the wall. For soil pipes and drainage ducts, size the core to the sealing system the specification calls for. Square or rectangular openings for ducting and trunking are cut with a saw and diamond blades, or by stitch drilling a line of cores.
Bit length and wall or slab thickness
Choose a bit long enough to cut the full thickness in one pass, because restarting in a part-cut bore is slow and can damage the bit. Where a wall or slab is thicker than the barrel, the hole is cut in stages, with the core broken out between them, or cut from both faces to meet in the middle on a line set out on each side. Allow for plaster, render, screed and insulation as well as the structural thickness.
HERMEQ holds permanent UK stock of these bits alongside the rest of its saws, drills and blades range, with next day delivery when a replacement bit or a different diameter is needed for the next job.
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Frequently Asked Questions
Can diamond core drill bits be used in an SDS drill?
The range is made for professional diamond core drills. These turn the bit at a controlled speed without hammer action and have the threaded spindle the bits fit. An SDS drill delivers hammer blows that chip diamond segments, and it lacks the gearing and torque to run a core bit at diameter, so a dedicated core drill is the tool for this work.
Can a diamond core bit drill through rebar?
A wet diamond core bit cuts through reinforcing steel along with the concrete around it, although progress slows while the segments are in steel. Cutting reinforcement in a beam, column or post-tensioned slab needs the structural engineer's approval, and the area is scanned for rebar before drilling.
How do you start a core hole without the bit wandering?
On a rig, anchor the stand to the wall or floor or hold it with a vacuum base, set it square and feed the bit gently until the segments have cut a full ring. With a handheld drill, start with the bit tilted so that one edge bites, then bring it upright as the groove forms.
Why has a diamond core bit stopped cutting?
A bit that spins without cutting has usually glazed, which means the bond has smeared over the diamonds and no fresh grit is exposed. This happens in hard aggregate, with too little feed pressure or at too high a speed. Dress the bit by making a few short cuts into an abrasive dressing block or a soft abrasive material such as breeze block, which wears back the bond and opens fresh diamond.
What affects how long a diamond core bit lasts?
The material sets the rate of wear first, since hard aggregate, dense reinforcement and abrasive masonry each wear segments differently. Steady water flow on wet bits, the correct speed for the diameter and firm, even feed pressure get the most cutting from each segment.