Diamond core drill bits, also known as diamond hole saws, are used to create holes in stone, concrete, glass and brick.  They are usually used with these harder materials and not for softer materials such as wood or softer metals.  The bit itself is made from a metal cylinder, generally fairly soft steel, and is placed upon an arbor.   An arbor is the spindle or axle upon which a revolving cutting tool is mounted.

The diamonds themselves (industrial) are placed at the open end of the cylinder and there are different ways of achieving this, for example vacuum brazing, nickel electroplating or metal sintering. The industrial diamonds are then welded onto metal sections secured at the end. The metal sections are thicker than the wall of the cylinder meaning most of the diamond bit does not rub into the hole being created.  Inevitably dust is created in the hole boring process but the cylinder wall has sloping openings which helped to carry dust away.

Depending on the thickness and hardness of the material, using a coolant like water or other lubrication is optional.  However coolants greatly increase the life of diamond equipment so their use is advised.

It takes less than 60 seconds for a 116mm diamond core drill bit, running at roughly 300 RPM to cut a 116mm diameter hole through a one brick thickness.  The hole created is smooth and has no ragged edges.  Drills with smaller diameters need faster speeds.

Diamond core drills tend to be less focused when drilling a flat surface so a drill press is needed to steady them.  A centering mechanism is needed if drilling by hand.  Templates made from stone or wood are another way to steady and focus the bit when starting to drill.  The centering mechanism is likely to be obsolete when the drill has reached 2 to 3 mm, although it still helps to reduce the wandering when boring a deep hole.

When using portable drills, diamond core drill bits  are available in a range of sizes from 6mm to 130mm.  The only restriction on the cylinder’s length and therefore the  depth of the hole, is the necessity to clear the dust away and thus remove the bit from the hole.  It is not uncommon to find 300mm cylinder length, but shorter bits are more common.  If a shank extension is used and by breaking off the core occasionally, the diamond core drill has the capacity to bore a hole several time its own length.

Some disadvantages of using diamond core bits are that they can bind if clogged with debris from drilling or if they are not held sufficiently in place so they wander away from the site of the planned hole.  If using a portable drill, it must be able to produce a fair amount of torque at a low speed.  Also it is sometimes best to have two operators when using larger drills as the recoil from a powerful drill is considerable under various conditions.  Long sided handles should also be used for additional safety.  It is obvious here that when working in confined spaces or at height, extra caution should be used with powerful drills.

Companies who sell or manufacture these specialized drilling tools and accessories include Hilti, Irwin and Makita.  Along with diamond core drill bits, there are many other types on the market including flexible, step and tile drill bits, brad point, glass, metal and long.

Using diamond drill bits is the most efficient way to make slots and holes from around 10 mm to 1 mm in diameter right down to almost unlimited depths.  Holes can be drilled into every type of brickwork and concrete to install electrics or plumbing.  It is also an efficient method of making holes of installing cables, pipes, load carrying devices and anchoring bolts.

Drill bits are placed on the moving end of different types of drilling machines which have diamond segments attached to the drilling end.  This method allows for minimal dust (if any) and is very quiet due to being powered by hydraulic or electric power systems.  For use in confined spaces, the tools can be used in inverted, vertical or horizontal or positions.  For irregular or larger openings, diamond stitch drilling can be used.  This is a technique where a range of holes are drilled next to each other to create an opening.

If you are new to diamond drilling, you can quickly improve your skills by learning some hints and tips.  It is both a science and an art and can be proficiently carried out by knowing the correct pressure and speed to drill, the proper coolants to use,  the appropriate accessories and choosing the right diamond drill for your material.

You should always wear the proper safety equipment including, safety goggles, footwear, head and hearing protection, respiratory equipment and well fitted clothing.   Before drilling, make sure there are no cracks in the drill by carefully visually checking it.  Check for run out too as this will significantly effect the hole’s shape affecting its circumference.  You can use a run out indicator specially designed for the job.

After you have carried our your initial safety checks, the next things to be aware of are firstly make sure you have your material held firmly in place before you start drilling.  Movement may cause the diamond part of the drill to break meaning damage to the material and possible injury to you!  Be careful not to use excessive pressure when drilling.

Drilling speed and pressure are also very important.  Using drills at their optimum will increase their life and reduce risk of material damage.  Drilling speeds vary with diameter of drill used, the coolant, diamond mesh size, drill wall thickness and material hardness.  As a guide, micro diamond drills from .001 inches need drilling speeds of 150,000+ RPM – quite high.  And much larger 48 inch diameter drills need lower 3 RPM.

Use coolant to wash out any excess debris.  Water is the best organic coolant and is clean, not leaving any greasy marks or contamination.  Other possible coolants are oils and air.  Always use coolant and remember, more coolant must be used the harder the material being drilled.

SDS drill bits are a type of shank. The drill bit is held by the drill’s chuck and its cutting edges are positioned on one end with the shank on the opposite end. There are many types of chuck and shank varieties which do different jobs for example, giving a larger centering accuracy or providing a higher torque.

In 1975 the German company Bosch developed the SDS drill bit. The name is derived from “Steck Dreh Sitz” in German, meaning Insert Twist Stay. The term “Spannen durch System” or clamping system may also be used in German speaking countries but Bosch uses “Special Direct System” internationally for consistency and ease of understanding.

SDS shanks are helpful for hammer drilling. Sliding keyways are used in the rotational drive. The keyways open to the shank’s end which then fits with keys in the chuck. The chuck holds the smaller areas which don’t open to the end and this helps to stop the drill bit loosening and dropping out. The flat end of the shank is hit by the hammer of the drill and the shank is covered with grease to enable the bit shank to move with ease in the chuck.

The SDS shank has a spring loaded chuck meaning it is easier to chuck the bits using a simple and fast one-hand action. Moreover, the chuck and shank are excellent for drilling into concrete and stone. The chuck does not hold the drill bit solidly but allows it to move to and fro, a bit like a piston. The hammer part of the drill works to increase the speed of the drill bit only and not the larger area of the chuck. This enables hammer drilling using an SDS drill bit hugely more productive than using the other available range of shanks.

SDS bits come in four sizes namely, SDS, SDS-plus (sometimes SDS+), SDSTop and SDSMax. The type most commonly found on the market is SDS-plus offering a range of drills for stone and brick work from 5mm in diameter to 30mm in diameter. Regarding length, the shortest are usually around 110mm with 1000mm being the longest.

Handy and portable power drills usually use the 1000 mm long drill bit and it is made solely for this purpose. However a shorter drill bit needs to be used first to create the bore, usually about a 400mm long bit will suffice for this purpose. The longer drill bits are very handy for wiring installations and plumbing in already existing stone or brick housing.

The SDS drill bits have excellent hammer drilling performance and have a fast one-handed chucking operation. They are rather complex to manufacture. The “rotation stop” feature can use chiselling bits. It has a high torque transmission but suffers with inaccurate centering.

Companies that manufacture or sell these specialised tools include Makita, Irwin and Hilti. As well as SDS drill bits, there are many other types on the market for different purposes including brad point, flexible, glass, long, metal, step and tile drill bits.