One of the most important tools in any metalworker's arsenal is the drill bit. Drill bits are cylindrical cutting tools that are used to create holes in various materials such as metal, plastic, wood, ceramic tile, and concrete. But not all drill bits are made the same, and choosing the wrong one can lead to disastrous results.
Using the wrong bit can result in damage to the material, decreased efficiency, and even injury to the user. Therefore, it's essential to understand the various types of drill bits available and their unique features, including materials, coatings, point angles, and lengths.
Whether you're a seasoned metalworker or just starting, this guide will equip you with the knowledge you need to make informed decisions and achieve the best results.
Drill Bit Materials
Here are the three most common types of drill bit materials:
High-Speed Steel (HSS)
High-speed steel (HSS) is a type of tool steel that is highly resistant to heat and wear. It contains tungsten, molybdenum, chromium, and vanadium, which provide increased strength and durability. HSS drill bits are suitable for drilling into soft metals, such as aluminum and brass, as well as wood and plastic.
- Advantages: HSS drill bits are relatively affordable, easy to sharpen, and have a long lifespan when used correctly.
- Disadvantages: HSS drill bits are not suitable for drilling hard metals, such as stainless steel, and can lose their sharpness quickly when used on tough materials.
Cobalt (HSCO) drill bits are made from high-speed steel with added cobalt, which enhances their strength and heat resistance. They can withstand higher temperatures and are less prone to dulling. Cobalt drill bits are ideal for drilling through hard metals, such as stainless steel, cast iron, and titanium.
- Advantages: Cobalt drill bits are highly durable, resist wear and tear, and maintain their sharpness for longer than HSS drill bits.
- Disadvantages: Cobalt drill bits are more expensive than HSS drill bits and require specialized equipment for sharpening.
Carbide (Carb) drill bits are made from tungsten carbide, which is a dense and durable material that can resist high temperatures and wear. They are ideal for drilling through hard materials, including ceramics, glass, and masonry, as well as hard metals like stainless steel and cast iron.
- Advantages: This type is incredibly durable, can maintain its sharpness for longer than other drill bit materials, and can handle high-speed drilling.
- Disadvantages: They are the most expensive of the three materials, and they can be brittle, which can cause them to break if they're not used correctly.
Design Features of Drill Bits
To choose the best drill bits for metal and other materials, you should consider the design features that affect their performance. These are the three key design features of drill bits:
Drill Point Angle
The drill point angle refers to the angle at which the cutting edge of the drill bit is ground. It is measured in degrees and can range from 90 to 150. A 118-degree angle is the most common, but other angles, such as 135 degrees and 90 degrees, may be more suitable for specific materials or applications.
Common Drill Point Angles
- 118°: Most commonly used angle for general-purpose drilling in metal, wood, and plastic. It is ideal for drilling softer metals, such as aluminum and copper. It also offers a balance between sharpness and durability. However, it may not perform well on harder materials.
- 135°: Better suited for drilling harder materials and alloys such as stainless steel, cast iron, and titanium. While it can handle harder materials, it may not be as effective on softer ones.
- 90°: It is used for creating countersink holes, deburring, and chamfering, but not suitable for drilling.
Drill Point Lengths
The drill point length refers to the distance from the tip of the drill bit to the beginning of the flute. There are three types of drill point lengths: standard, jobber, and long.
- Standard: Offers the most rigidity and is best suited for shallow holes in softer materials. Since it is rigid, it may not be suitable for deeper holes.
- Jobber: A versatile length that can drill holes of various depths and range of materials and is suitable for general-purpose drilling. While versatile, it may not be the best choice for drilling in hard-to-reach areas or extremely deep holes.
- Long: Offers the most flexibility and is ideal for drilling deep holes or in hard-to-reach places, but may be more prone to breaking or bending.
Flutes are the grooves that run spirally along the length of a drill bit. They serve to remove chips and debris from the hole as the bit cuts into the material. They are also typically wider and deeper on larger diameter bits. Flute design can greatly affect the performance and efficiency of a drill bit.
Types of Flute Designs
- Standard flutes: Standard flutes are straight and are found on most drill bits. They are versatile and suitable for most materials and drilling applications, but may not be the most efficient option for harder materials.
- Parabolic flutes: Parabolic flutes have a deeper flute design and are more efficient at chip removal, making them suitable for softer materials, such as wood or plastic. They may not be as effective for harder materials or larger diameter bits.
- Helical flutes: Helical flutes twist along the length of the bit, creating a longer cutting edge and improving chip evacuation. They are suitable for harder materials, such as metal or concrete, that require extra cutting power. On the other hand, they may be more difficult to control and require more force to start drilling
- Double flutes: Double flutes have two sets of flutes that run parallel to each other, providing extra stability and control for drilling straight or accurate holes in wood or metal. They provide extra stability and control, but may produce more heat and friction during drilling.
Drill Bit Coatings
Drill bits have different coatings, each with its features, advantages, and disadvantages.
Black oxide is a coating made by blackening the surface of the drill bit to enhance rust resistance and reduce friction. It is made from iron oxide and magnetite. They are best used for drilling soft metals such as aluminum, copper, brass, and mild steel.
- Advantages: Provides wear resistance and corrosion resistance. It also reduces friction, increasing the lifespan of the drill bit.
- Disadvantages: Not suitable for use on hard metals. It can also be easily scratched, which could affect the quality of the workpiece.
A bare metal finish with no coating. It is the most common type of drill bit. They are best used for drilling plastic, wood, and soft metals.
- Advantages: Easy to sharpen and provides good accuracy in drilling.
- Disadvantages: No rust resistance, and has a high friction level, causing heat buildup and reduced lifespan.
Titanium Nitride (TiN)
A gold-colored coating that provides heat resistance and hardness. It is made by depositing titanium nitride on the surface of the drill bit.
They are best used for drilling hard materials such as stainless steel, cast iron, and titanium.
- Advantages: Provides high heat resistance and hardness, which extends the lifespan of the drill bit. It also reduces friction and prevents galling and welding of the drill bit to the workpiece.
- Disadvantages: It is a relatively expensive coating.
Titanium Carbonitride (TiCN)
A gray-colored coating that is harder than TiN. It is made by depositing a layer of titanium carbonitride on the surface of the drill bit. They are best used for drilling abrasive materials like high-silicon aluminum, fiberglass, and carbon composites.
- Advantages: Provides a harder and more wear-resistant coating than TiN. It also has high lubricity, reducing the heat buildup and friction between the drill bit and workpiece.
- Disadvantages: It is more expensive than TiN.
Other Common Coatings Used in Drill Bits
- TiALN: A dark gray-colored coating that provides extreme hardness and heat resistance. It is best used for drilling hardened steels and stainless steel.
- Diamond-Like Carbon (DLC): A black-colored coating that provides superior hardness and wear resistance. It is best used for drilling non-ferrous metals and plastics.
- Zirconium Nitride (ZrN): A copper-colored coating that provides high wear resistance and low friction. It is best used for drilling aluminum and other non-ferrous metals.
Types of Drill Bits
When it comes to drilling, there are various types of drill bits designed for specific materials and applications. Here are some of the most common types:
- Twist Drill Bits: These are the most commonly used drill bits and are suitable for drilling holes in wood, plastic, and metal. They have a spiral shape that helps to remove the material being drilled and prevent the bit from getting stuck.
- Brad Point Bits: These bits are designed for drilling clean and accurate holes in wood. They have a sharp center point that helps to start the hole and two cutting edges that make clean cuts along the sides.
- Auger Bits: These bits are designed for drilling deep holes in wood. They have a long, spiral-shaped flute that removes chips from the hole as it is drilled.
- Spade Bits: These bits are designed for drilling large holes in wood. They have a flat, paddle-like shape with a pointed tip that helps to start the hole.
- Forstner Bits: These bits are designed for drilling flat-bottomed holes in wood. They have a flat, circular shape with a center point that helps to start the hole and cutting edges that create a smooth, flat bottom.
- Hole Saw Bits: These bits are designed for cutting large holes in wood, metal, and other materials. They have a circular shape with a saw-toothed edge that cuts through the material.
- Step Drill Bits: These bits are designed for drilling holes in metal and other hard materials. They have a stepped design that allows for drilling holes of different sizes with one bit.
- Masonry Bits: These bits are designed for drilling holes in concrete, brick, and other masonry materials. They have a carbide tip that can withstand the hardness of masonry materials.
- Glass and Tile Bits: These bits are designed for drilling holes in glass, tile, and other fragile materials. They have a carbide tip and a specialized design that reduces the risk of cracking or chipping the material.
- Countersink Bits: These bits are designed for drilling pilot holes and countersinks in wood and other soft materials. They have a tapered shape that creates a conical hole and a flat bottom for screws or other hardware.
- Drill Bit Sets: These sets include multiple types and sizes of drill bits for various applications. They are a great option for those who need a variety of drill bits for different materials and projects.
Each type of drill bit has its own unique features, suitable applications, advantages, and disadvantages. Choosing the right type of drill bit is essential for achieving accurate and efficient results in drilling.
Maintaining Drill Bits
If you want your drill bit to function optimally and improve its longevity, proper maintenance is a must.
- Store drill bits in a dry and clean location
- Keep them in their original packaging or a designated storage container
- Use a rack or pegboard to organize and prevent damage
- Avoid exposure to extreme temperatures and humidity
- Label the storage container for easy identification
- Sharpening and maintenance techniques
Sharpening and Maintenance Techniques
- Use a file or grinder to sharpen dull drill bits
- Keep the bit cool while sharpening to prevent overheating and damage
- Remove any burrs or chips on the cutting edge
- Check the bit regularly for signs of wear or damage
- Use lubricant or cutting oil during drilling to reduce friction and heat buildup
- Avoid applying excessive pressure during drilling, which can cause wear and damage to the bit.
Common Mistakes to Avoid When Using Drill Bits
When it comes to using drill bits, mistakes are not uncommon. These are some of the most common mistakes that you should avoid to ensure safety:
- Using the wrong drill bit: Choosing the wrong type or size of drill bit can damage the material being drilled, the drill bit itself, or even the drill. Always use the appropriate drill bit for the material and project being worked on.
- Applying too much pressure: Applying too much pressure on the drill can cause the bit to bend or break, damage the material being drilled, or cause injury to the user. Let the drill do the work and apply gentle and steady pressure to avoid damaging the bit or material.
- Overheating the bit: Overheating the bit can cause it to become dull and ineffective, or even melt and break. Use the proper speed setting for the drill, and apply lubrication or cooling agents to reduce friction and heat buildup.
- Neglecting to use safety gear: Failure to use proper safety gear such as safety goggles, gloves, and earplugs can lead to injury or long-term health problems. Always wear the appropriate safety gear when using a drill to protect yourself from flying debris, loud noises, and other hazards