Metric sizes measure the diameter of the drill bit using standard metric lengths.  Standards organizations such as the British Standards Organization, or BSO, define the sizes and it is those sets of sizes that we commonly see in retail outlets today.  In 1959 the BSO published the new metric drill bit sizes when the industry moved from gage measurements to metric.

The smaller sized drill bits are made in smaller increments of diameter.  The availability and price of drill bits does not move in uniform with the range of sizes.  A set of drill bits at size increments of 1 mm are most commonly found in shops or DIY stalls and they are usually the most cost effective.  Builders merchants usually stock 0.1 mm increments.  Hardware shops usually stock 0.5 mm increments.

Other than bits under 1 mm diameter, it is unusual to find drill bit sets in sizes smaller than this.  Unusual sizes like 2.50 mm for example are required for specialized tasks and need to be specially ordered through a supplier.  With number gage drill bits, it is common to easily access every size range on the market.

In the USA, fractional inch drill bits are commonly used just as they were in other parts of the world.  But metric dimensioning is increasingly favored.  There are however some disadvantages to the fractional inch incremental measurements such as, for the smaller drill bit sizes, the increment between the measurements is quite large at 100%.  This means that number gage bits are needed to compensate for the gap.

Regarding letter gage and US number sizes of drill bit, both of which are commonly used in the US today, the operator is required to used a chart of drill bit sizes to work out the size of bit needed for the task in hand.  With metric, this is not necessary.

Number gage is similar but different from the American wire gage system used for the diameters of nonferrous, round and solid wire that conducts electricity.  Number gage is used from size 1, the largest measurement, to size 80, the smallest.

Letter and number gage drill bits are normally always twist drill bits.  The gage can be used to measure other types of bit however, the twist drill bit is commonly used in a size range covered buy  the gage.  There is no actual set formula that is used by the gage to diameter size conversion, however it is seen as a useful measure.

So, there are many different ways to measure drill bits, but the metric system is widespread.  Companies that supply metric drill bits and drill accessories include Hilti, Makita and Irwin.   There are many types on the market including tile drill bits and brad point bits, long and short bits, glass and metal, ceramic, flexible, step drill bits.

Cobalt drill bits can be used on extremely hard, high tensile strength materials like hardened stainless steel (precipitation-hardened), Inconel alloys, cast iron, and titanium but they are also used on softer materials like plastic. They are often used in the aviation industry.

There are two grades of cobalt bit. M35 has 5% cobalt added to raise resistance to heat and M42 has 8% of cobalt added to utilize its wear resistance properties as it is less prone to breaking and chipping compared to other bits. The most popular types of cobalt drill bit are jobber length, numbered measured, fractional measured, 6 inch and 12 inch extended length.

Bosch cobalt drill bits include an alloy that enables bits to heat to 1,100 degrees Fahrenheit and drill for an extended length of time at these higher temperatures. These temperatures that would normally destroy other bits made from less heat resistant material. They last longer in highly abrasive materials. The overall bit hardness can be increased to 68 HRC which is ideal for drilling in abrasive or tough materials. A thick web design increases the rigidity and prevents the drill bit from snapping when drilling in very hard and abrasive materials. The higher red hardness of cobalt allows speeds of up to 30% higher than other drills.

Twist drill bits are made from a range of materials including cobalt, carbon, black oxide and titanium. The functionality of the drill dictates which of these materials is included – each is designed for a particular purpose. Some materials are hard and require a drill that is resistant to wear and tear and high temperatures. Some materials are softer, so softer metals can be used in making the bit. Each bit has its specific purpose. Bits with black oxide in their formula are for general purpose use for heavy duty drilling in carbon, plastic, soft cast iron and aluminum.

Cobalt alloys hold their hardness at extremely high temperatures, more so than standard bits but their main disadvantage is that they are more brittle and can therefore snap more easily than regular drill bits. Cobalt bits are not coated, they are made solely of cobalt. When manufacture is almost complete, the bit is baked at high temperatures in a special industrial oven which changes the surface color to a subdued golden color. This is mainly done to enable color identification from other bits. Even if the gold color wears away through use or sharpening, it is still solid cobalt steel through and through.

Irwin is a popular drill manufacturer who use M42 grade (contains 8% cobalt) in their bits. A correctly sharpened a cobalt bit is still as good as a brand new bit – its performance is not affected. However, sharpening other coated or tipped drill bits such as titanium for example, the performance is decreased in effectiveness as the coating is worn away.

Companies that supply drill bits and accessories include Makita, Hilti and Irwin as mentioned. Along with cobalt drill bits, there are many other types on the market including tile drill bits and brad point bits, long and short bits, glass and metal, ceramic, flexible, step drill bits.

HSS grade bits usually give high abrasion resistance due to the presence of the element tungsten, widely used in HSS.  It also has high hardness (greater than HRS 60) when compared to the more common tool and carbon steels.

High speed steel is mostly used in the manufacture of a range of cutting tools such as taps, tool bits, drills, saw blades, gear cutters, milling cutters.  Most often however, it is seen in drill bits and power saw blades and also dies and punches.

Fine hand tools such as pocket knives, files, hand plane blades, chisels and fine quality kitchen knives are also made with high speed steels.  Because of their greater resistance at high hardness and abrasion – more than carbon steel – this enables them to be operated at the speeds needed for making these finer tools which need a sharp but durable edge.

When undertaking high speed drilling operations, ordinary high-carbon steel does not have the heat tolerance or durability to manage such tasks.  Special tool steel has enhanced properties when blended with any one of these various elements: chromium, molybdenum, cobalt, vanadium or tungsten.  This is called a multi component alloy system Fe-C-X of which HSS is a part.  X can be any one of these listed metals depending on the property desired.

When the alloy of the steel is varied this makes HSS bits suitable for a wide range of tasks in different areas of industry.   Some alloys increase flexibility and impact strength and others improve durability of the cutting edge and raise the working temperature.  The addition of molybdenum for example increases the flexibility of the HSS bit.  It also raises the maximum working temperature and increases wear resistance and toughness.

Adding other elements customizes HSS steel to specific industrial needs. Some elements increase impact strength and flexibility while others raise the maximum working temperature and durability of the cutting edge.

High Carbon:  adding this to iron makes steel which is stronger and harder than iron.  It can be tempered to a range of hardness levels.

HSS alloys: the HSS label refers to a few different alloy steels which are used in HSS bits.  For example,  chrome-vanadium steel is doesn’t give out as quickly at high drilling speeds and tempers harder than pure high carbon steel.

Companies that supply drill bits and accessories include Hilti, Irwin and Makita.  Along with HSS drill bits, there are many other types on the market including step drill bits, flexible, tile drill bits, brad point, long and short bits, glass and metal.

Masonry drills are mainly used in power drills, however they can also be used in a hand brace although it will require a lot of effort to do this!  It is possible to use  a hammer action power drill with the majority of masonary bits.  However, the action puts a lot of stress on the bit and lesser quality bits tend to break when pounded but generally, masonry bits are usually used with a hammer drill.

The bit is turned in a circular motion whilst hammering into the material.  The hammering action breaks apart the masonary at the tip of the drill bit and the indents in the body of the bit carry the dust away.  With every hammering action, the rotation of the bit enables the cutting edges onto a new area of the hole’s base.  Special shanks are often used with hammer drill bits.
Remember to constantly withdraw the bit to flush out the drilling debris and when drilling harder materials, make sure to always use a slow rotational speed otherwise the tip will overheat.

Masonry drill bits are usually available from 5mm to 40mm.  Core bits are used for larger diameters.  Hand portable power tools are used with drill bits up to 1000mm and they good for installing plumbing and wiring in established buildings.

Drill bits come in a range of shapes and sizes and it’s vital to use the appropriate drill bit for the task in hand.  Not all bits do all jobs.  Drills don’t normally come with bits, so you will need to purchase them separately.

If you are drilling masonry, you will require a masonry drill bit which are specially designed for boring into brittle and hard materials like concrete, stone and brick and are the only bits that a hammering action can be used with as they won’t shatter.  It pulverizes the material being drilled and with a rotary motion, it brushes debris from the hole.  When drilling into tiles however, the hammer action should not be used.  The drill bit can become extremely hot when drilling masonry, so take care to avoid burns.

Take care to remove all the dust from the hole as it can get clogged in the drill bit, choking it which wastes the drill’s power and can lead to the drill bit breaking and getting stuck in the hole.  To avoid this, especially when drilling downward holes, use a pumping action.

When debris from drilling clogs the hole, this can prevent the insertion of a wall plug.  A trick is to use a bendy straw and blow the dust out taking care to close your eyes while blowing.  Ask a helper to vacuum up the dust you blow out as you blow to make cleaning up easier.  Another handy trick to ease cleaning up when drilling inside the home is to stick an envelope below your designated hole area before you drill to catch the dust.

There are several main companies that make and supply drill bits and accessories including Hilti, Irwin and Makita.  Along with masonry drill bits, there are many other types on the market including step drill bits, flexible, tile drill bits, brad point, long and short bits, glass and metal.

Sometimes however, solid carbide drills are available for use in certain industries for example PCB drills (printed circuit boards) where many holes are needed.  The boards are made of fiberglass which is extremely abrasive and would ruin most other bits, so solid carbide tungsten twist bits are used, providing a longer life.

Drill bits undergo high stress and the constant rotation creates friction and therefore heat.  This makes the bit a little duller after every use and the continual cycle of heating and cooling eventually compromises the internal structure of the bit.

Regular non-carbide bits wear out and break very quickly.  Coated bits such as titanium carbide or titanium nitride coatings raise the lifespan of a bit.  They will stay sharper and last longer and are the strongest bits available for domestic use.  When drilling very hard and dense materials such as stainless steel, carbide bits are able to take the strain where most other bits would break.  A carbide bit will last up to 24 times longer than a regular drill bit meaning they are an economical option for carpentry and furniture building where hard materials are used.

To lengthen the life span of the bit, using a lubricant can help when drilling dense material.  It cools the drill bit as it drills and avoids excessive heat which can reduce the lifespan of the drill bit.  Also do not press too hard when drilling as this will dull the bit.  It can seem like this is helping, but it is important to allow the drill bit to do the work.

When drilling at high speeds, carbide and also ceramic tools are needed.  While they may not be as tough at high speed as other materials, they have greater heat and wear resistance.  Choosing the right coolant is paramount as different materials being drilled have different properties.  With some the cooling effect is critical and with others, lubricity is needed.

Solid tungsten carbide, high-temperature grade is the most common material used for high speed drills.  Chatter can sometimes be a problem but there are different grades of carbide and using a finer grade at high speed is key, such as a grain size of 0.5 microns compared to the more standard 2.5 microns.  Finer grain carbide tools keep their toughness while resisting wear and tear at the same time.

Some solid carbide bits have a tough core made from two grades of  cemented carbide sintered together.  The core is also high strength grade and used for low speed center performance.  For high speeds, wear resistant, low grade is used.

Companies that supply drill bits and accessories include Makita, Hilti and Irwin. Along with carbide drill bits, there are many other types and styles catering for different jobs on the market including long and short bits, glass and metal, ceramic, flexible, step drill bits, tile drill bits and brad point bits.
Carbide drill bits provide industries with a versatile material used for low and high speeds, industrially as well as in the home.

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.

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.