How To Choose and Use Drill Bits

Using the right drill bit is incredibly important for any drilling project, whether you’re a DIY enthusiast or a seasoned pro. With so many drill bits available, it’s essential to understand which type works best for your material and project. Tom Silva, Ask This Old House general contractor, shares his expert advice on how to select and use drill bits effectively in the video above.

Drill Bit Basics

Before diving into specific types of drill bits, it’s helpful to understand some basic factors that affect their performance and which materials they’re best suited for.

Drill bits come in various materials, each designed for specific uses:

• High-speed steel (HSS): Great for drilling wood, plastic, and soft metals.
• Cobalt: Ideal for drilling harder metals and alloys.
• Carbide-tipped: Excellent for masonry and concrete.
• Titanium-coated: Offers increased durability and heat resistance.

The coating on a drill bit also influences its performance and longevity. Some standard coatings include:

• Black oxide: Improves heat resistance and reduces friction.
• Titanium nitride: Increases hardness and wear resistance.
• Diamond powder: Enhances drilling performance in abrasive materials like tile or stone.

Types of Drill Bits and Their Uses

Different drilling tasks require specific types of drill bits. They come in various sizes, typically measured in fractions of an inch or millimeters. The shape of the bit’s tip determines how it cuts through different materials. Understanding each type’s strengths and limitations will help you choose the right bit for your project.

Twist Bits

Twist bits, also known as HSS bits, are the most common and versatile. They’re ideal for drilling small, uniform holes in various materials like wood, metal, and plastic. The bit’s spiral flutes help remove the material as you drill, and the pointed tip offers precise control.

Spade Bits

Spade bits are best for drilling large, rough holes in wood. They have a flat, paddle-like shape with a sharp central point and cutting edges. Spade bits work fast, but they’re not recommended for finished carpentry projects where clean cuts are important.

Brad Point Bits

Brad point bits are specifically designed for precise drilling in wood. They feature a sharp center point, or brad, that helps position the bit exactly where you want to drill. This makes them perfect for woodworking projects where accuracy is important, such as drilling dowel holes or pilot holes for screws. They’re common in furniture making or cabinetry.

Forstner Bits

Forstner bits are perfect for woodworking projects where you need clean, flat-bottomed holes. Their circular cutting edge produces smooth walls, and the center point ensures accurate placement. These bits are great for drilling overlapping holes or precise work in furniture and cabinetry.

Countersink Bits

Countersink bits are useful for setting screws flush with or below the surface of your material. They combine a drill bit and countersink into one tool, which saves time and guarantees the screw head sits perfectly in your woodwork.

Specialty Drill Bits for Unique Applications

Beyond the more common drill bits, specialty bits designed for specific tasks exist. These tools can make challenging drilling jobs significantly easier and more precise.

Masonry Bits

Masonry bits are perfect for drilling into rigid materials like concrete, stone, and brick. They typically feature a carbide tip that withstands the hardness of these substances.

Masonry bits typically include tungsten carbide tips that resist wear, making them highly durable. They have spiral flutes that channel dust and debris away from the hole during drilling. You’ll see these bits paired with heavy-duty or hammer drills for tough jobs.

Glass and Tile Bits

You’ll need specialized bits to drill delicate materials like glass and ceramic tiles. These bits often have a spear-shaped tip that reduces the risk of cracking or shattering the material. Slow drilling speeds and steady pressure are key when working with glass and tile.

Step Bits

Step bits are a versatile tool for drilling holes of various sizes in thin materials like sheet metal and plastic. Their cone shape allows you to drill holes in multiple sizes with just one bit. These bits are often used in electrical work and are great for deburring holes as you go.

More Considerations for Drill Bits

Beyond material, selecting the right drill bit depends on the size and depth of the hole you need. If you’re working on precise holes or deeper projects, choose a bit that matches your desired hole size and depth. For smaller holes, twist or brad point bits are best. For larger holes, spade or Forstner bits will get the job done.

Also think about the specific needs of your project when selecting a drill bit:

• For finished woodworking, use brad point or Forstner bits for clean holes.
• For rough construction, spade bits or twist bits may suffice.
• For installing hardware, countersink bits give proper screw seating.

Proper Drilling Techniques

Follow these general tips for the best results:

• Start with a pilot hole for larger bits to improve accuracy.
• Apply steady pressure while drilling and let the bit do the work.
• Adjust the drill speed depending on the material and bit type.
• When drilling metal, use cutting oil to reduce heat and extend the bit’s life.

Safety Considerations for Drill Bits

Always prioritize safety when using drill bits:

• Wear safety glasses to protect your eyes from debris.
• Use work gloves to guard against sharp edges and hot metal shavings.
• Secure your workpiece to keep it from moving as you drill.

Resources:

Silva discusses a variety of different drill bits that all serve specific purposes. In general, consider the size of the hole that needs to be drilled and what material the hole needs to be drilled into. This will help you determine which drill bit will work best for your project.

You can find all the drill bits Silva demonstrated, including the HHS bit, masonry bit, spade bit, and Forstner bit, at local home centers.