What makes each kind of drill bit special, and when should you use them? The topic of drill bits is a big one because of the large variety of bits. There's a drill bit designed for just about every thinkable material and drilling need. Because there's so much crossover between applications, sizes, and materials, the best way to approach the untangle the world of drill bits is to categorize them by design. Let's start with some fundamental information about drill bits.

Parts of a Drill Bit:

Most drill bits have the same essential parts, being familiar with those parts and understanding how each bit design is manufactured for its specific job will make your life easier in the long run.

Shank - the non-working end of the bit that fits into the drill chuck. Shanks are mostly perfectly round but sometimes include design features to reduce slippage in the chuck, such as Viking Drill's Thunderbit or Nitro's 3 Shank bits.
Lip- the lip or lips of a drill are the cutting edges and can be positioned in different places on the bit, depending on its design and application.
Flute - the grooves in a drill bit that allow and direct the material as it leaves the hole being drilled. Boring or coarser drilling bits have wider, deeper flutes for faster material removal.
Tip - Kind of obvious - the working end of the bit opposite of the shank.

Drill Bit Sizes and Measurements

Standard drill bits are most often sized in fractional, 1/64" increments, commonly ranging from 1/16" up to 1". Bit size may also be labeled in millimeters and decimals. After knowing what bit design and other features you need for an application, measurements like bit length, diameter, and tip angle are necessary to further match the bit to the job.

Bit Diameter- This is the diameter of the working end of the drill bit or its tip.
Tip angle - The most common tip angles for drills are 118° (softer materials) and 135° (harder materials). As a general rule, the harder the material, the broader the drill tip angle to reduce "walking."
Shank Diameter- the diameter of the shank that fits into the chuck.
Flute Length- this is just the cutting portion of the bit.
Overall Length- Length of the entire bit from the end of the shank to tip.

What the Drill Bit is Made Of

Many drill bit materials offer a variety of degrees of wear-resistance, strength, and lasting sharpness. The most crucial factor to consider when choosing a bit material is the material you are drilling into. Carbon steel bits may be able to cut through some metal materials, but it may also cause heavy wear on the bit. The harder the bit material, the more expensive and brittle they become, carefully choosing a bit can save you money in the long run.

Carbon Steel - The most common and least expensive. Carbon Steel bits do not hold an edge well and require frequent sharpening. They are used for softer wood materials and plastics. Note that even working with hardwoods rather than softwoods can noticeably shorten their lifespan.
High-Speed Steel (HSS) - These bits go through an additional tempering process that hardens them and upgrades a traditional carbon steel bit. HSS bits last longer and can cut through harder materials, but excessive heat during use can damage them. They can also be used to drill plastic, iron, steel brass, copper, and aluminum alloy.
Cobalt Steel - By mixing higher concentrations of cobalt into the steel alloy improves the high-speed steel bits so they can withstand high temperatures. This lengthens the life of the bit but increases the brittleness. Cobalt bits work great for treated stainless steel, cast iron, and they even work on titanium. These bits are very heat resistant, which is excellent considering the heat that builds up while you're drilling into metal, also when you're using lubricants.
Titanium Coated - Titanium ceramic coatings are used on some drill bits and can make them last three to five times longer than high-speed steel drill bits. The coating makes the cutting edges sharper but cannot be sharpened without losing the coating benefit. They're great for working on wood, softer metals such as magnesium and aluminum, and even plastic, but don't do well with harder metals such as stainless steel or cast iron. Relative to cobalt bits, titanium bits should be thought of as being far more disposable.
Carbide - Carbide bits are often "tipped," much like titanium bits. Carbide is a sturdy material, making these bits the hardest of them all and the most expensive. When needed for stainless steel and other hard metals, no other bit can keep up in performance and durability. Carbide bits are best used on cast iron, nonferrous heavy metal, and other abrasive materials.

Many design details work together to fit a drill bit to its application. The aggressiveness of bit, how fast it ejects material, its target material, and drilling speed is determined by how much twist is in the bit, tip angle, and lip angle. Specialty bits have more drastic design changes, and sometimes need a little extra information for purchasing.


	Brad-Point A fluted drill bit is designed for use on wood. It features a sharp tip and spiral flutes. The tip helps position the bit in the correct spot, and the flutes expel the wood chips from the hole as you drill. Brad-point bits make quick work of jobs that require a high degree of detail.
	Twist The twist bit is a general-purpose bit for home use and can be used on wood, thin metal, and plastic. The bit has a pointed cutting tip and, like the brad-point bit, features fluted sides to remove waste.
	Counter Sink Designed to create a pilot hole with a wider opening at the top for countersinking screw heads. When used on wood, the bit allows you to insert the fastener deep enough, so the head doesn't protrude above the surface.
	Forstener Used on wood and features the same tip spur as a brad-point bit for precise drilling, but the body of the bit is designed to drill a flat-bottomed hole to hold dowels.
	Spade A Spade or Paddle bit comes with a tip spur for precision, and a flat blade is designed to cut holes up to 1.5 inches. Spade bits are commonly used to drill holes through wood studs to run wires or water-supply lines.
	Hole Saw Comes in two pieces, the bit cylinder and a mandrel that attaches to the bit and fits into the drill. It is used for making large holes in wood, thin plastic, ceramic tile, and other sheet goods.
	Step This bit is primarily used to enlarge existing holes on sheet metal or plastic. A step drill bit can also take the place of a countersink bit by widening the top of a hole just enough to recess the fastener head.
	Left-Handed Primarily used for drilling out screws or bolts that have snapped off in a hole. Made of extremely hard metals and the counterclockwise direction of the flutes helps loosen the fastener. A left-handed bit won't further tighten the stuck fastener as a right-hand one can.

Which drill bit is right for you depends on what materials you're going to be drilling. If you're going to be working exclusively with harder metals, like stainless steel and cast iron, you'll be better off with a cobalt bit due to its superior durability and the ability to sharpen the bit. If you're going to be working with softer metals and wood, then you can't go wrong with a titanium drill bit, and available at a lesser price, so if the cost is what's most important to you, then the titanium drill bits will serve you better.