Carbide drill bits are the among the hardest and most expensive in the industry.  Carbides and tungsten carbide are a very hard materials with the ability to drill into almost every material but still maintaining an edge longer than other drill bits.  Carbides are usually only found in tipped tools due to their brittleness and cost.  Small pieces are brazed or screwed onto the end of a bit.

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.

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.