Not all drill bits are the same. Because different projects have different needs, drill bits come in a variety of shapes and are made from different materials based on the task they are designed to perform. Choosing the wrong drill bit can lead to structural flaws in the project, broken bits, and even damaged drills. Selecting a bit that is made from the right material will help ensure the hole drilled has a smooth edge and that none of the equipment being used is damaged in the process. To a large degree, selecting the right drill bit material for a project depends on the material that will be drilled through and the hardness of the material used to form the drill bit.
The best way to determine what drill bit is right for the job is to have an understanding of all the available types and make an informed decision based on that understanding.
History of Drill Bits
The earliest drills were developed by the ancient Egyptians, and were simply a lath powered by the back and forth motion of a bow. Later, drill bits were attached to a handle and worked through wood with a cranking motion. It was not until 1889 that Australians Arthur Arnot and William Blanch Brain developed the first electric drill. Unfortunately, this device was large and awkward, and though it worked well, it was not convenient for household use. The first portable drill was released in 1895, and the pistol-grip design was patented by Black & Decker in 1917. This design is now used in most drill options. The first battery-powered drill was released in 1961. It used a 7.2 volt nickel-cadmium battery and only worked for about 20 minutes before needing to be recharged.
Drill Bit Materials
There are a number of metals used to make drill bits. Each material is best suited to drill through a particular type of surface. It is important to understand the strengths and weaknesses of each material type when selecting the bit for any project.
Low Carbon Steel
Low carbon steel drill bits are appropriate for drilling softwoods only. They are too soft for use with hardwoods and metals, and tend to dull frequently; they also need to be sharpened often to improve their lifespan. Despite these flaws, they have the distinct benefit of being extremely inexpensive.
High Carbon Steel
High carbon steel bits have a higher temperature tolerance than low carbon steel bits, so they hold up to wear better and require less frequent sharpening. They are suitable for drilling thin metal and hardwood surfaces. They cost about the same amount as low carbon steel bits and are a better option for basic drilling.
High-speed steel bits, sometimes called HSS drill bits, are made of an extremely hard carbon steel that has a higher heat resistance than high carbon steel. This allows them to be used at higher drilling speeds, and insures that the bits maintain their structural integrity longer. HSS bits can be coated to improve certain features, and their porous surface holds coatings well.
Carbide tipped drill bits are specialized tips on hardened steel bits. Carbide tipped drill bits have the ability to dissipate heat rapidly, and so will hold an edge longer and tolerate heat better than other drill bit options. Unfortunately, carbide tipped bits are very brittle and will chip if they are not handled with care. They are appropriate for drilling hardwood and thin metals.
Cobalt drill bits are extremely hard and are useful in boring into material too hard for standard high-speed drill bits like stainless steel and other thicker metal surfaces. Cobalt is less susceptible to heat damage than any other drill bit type, but it is also extremely brittle and prone to accidental damage.
Diamond Drill Bits
Polycrystalline diamond drill bits, sometimes simply referred to as PCDs, are made of the hardest drill bit material available on the market. The bits are made by coating a carbide bit in diamond particles. Diamond drill bits grind away the surface they are drilling into, rather than cutting into the surface. They are appropriate for cutting through a variety of extremely hard surfaces including granite, ceramic tile, marble, fiberglass, stone, glass, and heavy metals.
Drill Bit Coatings
Drill bit coatings make the drill bit harder, more lubricated, sharper, or more heat resistant than the metal bit is on its own. Coatings significantly improve the cutting quality, durability, and lifespan of drill bits.
Black oxide is the most basic and inexpensive coating. It is commonly used on high-speed steel bits and provides a higher level of heat resistance and improved lubrication. It also protects the bit against water damage, rust, and corrosion.
A titanium nitride, sometimes called TiN, coating reduces friction during drilling and increases heat resistance. Coating a drill bit with titanium nitride can increase the life of the bit up to 5 times. It also allows for faster drilling speeds.
Titanium Aluminum Nitride
Titanium aluminum nitride, sometimes referred to as TiAIN, is designed to increase the hardness and temperature resistance of the bit. Bits with a TiAIN coating are heat resistant up to 800 degrees Celsius, and cling well to a variety of base bit types.
Zirconium nitride strengthens brittle drill bit types and decreases friction. It is an excellent coating for drill bits that will be used for precision drilling. It is also effective at reducing the risk of accidental damage on brittle bit types caused by rough handling and basic wear and tear.
Specialty bits are made of rarer materials and often have a specifically designed shape that makes them perfect for a certain project. These bits are generally more expensive and harder to find than more traditional drill bits.
Tungsten carbide bits are extremely expensive and extremely brittle. This material is only used to make very fine drill bits. Typically tungsten carbide drill bits have a diameter of less than 1 mm. They are useful in small space drilling situations, and are hard enough to withstand the wear and tear of drilling through abrasive materials.
Diamond core drill bits are used in stone cutting and masonry. Instead of the traditional point and auger style drill bit, these are hollow tip drill bits that cut or grind a circle using the outer edge of the bit. The core drill bit cuts a core or plug from the stone or glass it is used to cut, so that there are fewer shavings and potentially harmful shards of material when the drilling project is complete.
Masonry bits are made of hard carbon steel but have a specialized tip made of a harder metal. The tip is typically welded into the end of the drill bit. These bits are designed to cut through concrete, brick, and mortar during the masonry process.
PCB Drill Bit
PCB drill bits are a type of micro-drill bit that has a diameter of 1 mm or smaller. They are designed to bore holes in the electronic computer boards of most electronic objects. Because they are so fine, they are commonly made of carbide, which can hold up to the fiberglass board better than the alternatives.
Flexible Shaft Bit
Flexible shaft bits are made of spring steel and are designed to flex while drilling. They can be bent while in motion so that the hole drilled can curve inside of walls and create uniquely shaped holes. They are commonly used when running wiring in homes or doing construction work in areas with limited workspace.
Shopping for Drill Bits
When shopping for a drill bit, consider how and where the bit will be used. Begin by deciding which material is best for the job, and then select a tip type and a size. It is often necessary to buy multiple tips, in multiple sizes, to complete a project. Buyers can save money by buying a set of drill bits in multiple sizes. Remember that it is important to select bit styles and materials that are appropriate for the project, because failure to do so may cause damage to the bit, the drill, or the project at hand.
Buying Drill Bits on eBay
If you're ready to buy a drill bit on eBay, head to the Home & Garden department, continue to the Tools section, and then proceed to the Power Tools section. From there, continue to the Drill Bits subsection and begin looking through the various options available to you. You can also take advantage of the Location, Price, and Condition search modifiers in order to find the drill bits that are right for your budget.
Make sure to read consumer reviews of the drill bits under consideration and read the product details to make sure the drill bit is compatible both with the drill and the project they will be used on.
Drill bits are used for boring holes through a number of surfaces including walls, wood, sheet metal, computer hardware, masonry projects, and more. Because drill bits are used on such a variety of surfaces, tool companies have developed drill bits in a growing number of materials and styles to accommodate the unique needs of every drilling project. Take the time to research what drill bit is right for a project before making a purchasing decision to ensure the bit selected is hard enough to bore through the material at hand and create a hole with smooth even edges.