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Types of Drill Bits: Complete Selection Guide
Drill bits are the unsung heroes of manufacturing, construction, and DIY projects. Choosing the wrong type can lead to broken tools, damaged materials, and costly delays. This guide cuts through the confusion, explaining 15+ drill bit types, their industrial applications, and pro tips to maximize efficiency.
Contents
What are Drill bits?
Drill bits are cutting tools mounted on drills or drilling machines. They create holes in materials through rotation or impact, widely used in metalworking, woodworking, construction, and electronics manufacturing. While shapes and sizes vary, all drill bits share the same basic components:
Shank
The shank is the rear part inserted into the drill chuck for fixation.
Flutes
Spiral grooves running from the cutting edge to the shank. They remove chips during drilling and allow coolant to reach the cutting area, reducing heat buildup.
Point
The tapered tip of the drill bit, consisting of cutting lips and a chisel edge for centering.
Cutting Lip
The sharp edge that directly contacts the material, performing the primary cutting action.
Differences between drill bits mainly lie in cutting lip design, which determines material compatibility (e.g., a split-point tip for metal vs. a brad point for wood). Drill bit designs also adapt to specific tools—for instance, masonry bits for hammer drills have reinforced flutes to handle concrete vibration.
How to Select the Right Drill Bit?
Choosing the right drill bit starts with defining your application. While general-purpose bits work for basic tasks, specialized bits deliver better results for specific materials and hole types.
Drill bit material and coating directly impact compatibility with workpiece materials:
Drill bit materials:
- Carbon Steel
Made from standard carbon steel. Best for soft materials like pine wood or thin plastics in low-intensity tasks. - High-Speed Steel (HSS)
Contains tungsten (W), molybdenum (Mo), chromium (Cr), and vanadium (V). Handles wood, plastics, and soft metals (e.g., aluminum sheets) at moderate speeds. - Cobalt (5–8% Co)
Added cobalt boosts heat resistance and wear life. Ideal for stainless steel, titanium alloys, and other tough metals—common in aerospace or automotive repair shops. - Tungsten Carbide
With a hardness of HRA 90–94 (far exceeding HSS and cobalt), it drills hardened steels, ceramics, or glass fiber composites. Fragile but unmatched for abrasion resistance. - Carbide-Tipped
Steel body with a carbide cutting edge. Balances durability and cost—popular for high-volume production on cast iron or alloy steel. - Polycrystalline Diamond (PCD)
Synthetic diamond edges. The “king of non-ferrous materials,” perfect for graphite, carbon fiber, or copper-aluminum alloys in electronics manufacturing.
Drill bit coatings:
- Titanium Nitride (TiN)
Gold-colored layer reduces friction and wear. Extends bit life for steel and iron drilling—think garage mechanics or metal workshops. - Titanium Aluminum Nitride (TiAlN)
Purple-black coating. Better heat resistance than TiN, suited for high-speed drilling in stainless steel (e.g., kitchen fixture installations). - CVD Diamond Coating
99% pure diamond layer. Highest hardness but costly. Reserved for abrasive composites like carbon-fiber-reinforced polymers (CFRP). - Black Oxide
Economical anti-rust coating. Works for carbon steel drilling but avoid aluminum—it can cause material buildup and bit jamming.
You may have heard of PCD and SDS drill bits. Let’s clarify what they are:
PCD Drill Bits
Made from synthetic diamond, as mentioned in the materials section. Dubbed the “king of non-ferrous materials” due to diamond’s extreme hardness, these bits excel at drilling composites (e.g., carbon fiber panels), aluminum alloys, and graphite—common in aerospace fuselage assembly or EV battery case production.
SDS Drill Bits
Designed specifically for hammer drills. Their shanks feature grooved locking mechanisms that allow quick installation and efficient transfer of impact energy. Primarily used for drilling into concrete, brickwork, or stone masonry—think construction crews installing anchors in high-rise buildings or renovators breaking through load-bearing walls.
Types of Drill Bits
Drilling operations require different drill bit types. We’ll analyze them from three perspectives: material-specific applications, specialized designs, and shank types.
Material-Specific Selection Guide
Choosing the right drill bit starts with the workpiece material, which determines coating, composition, and cutting edge geometry. Common categories:
Drill bit for masonry
For concrete, brick, or stone: Use carbide-tipped masonry bits or SDS-Plus bits designed for hammer drills. These combine HSS bodies with tungsten carbide cutting edges to prevent cracking, reduce noise/dust, and withstand impacts—essential for drilling anchor holes in foundation walls or installing HVAC systems.
Drill bit for metal
Match bit hardness to the metal:
HSS bits handle soft metals (e.g., aluminum sheets in automotive body shops).
Cobalt bits (5–8% Co) tackle stainless steel pipes or hydraulic fittings.
Tungsten carbide bits drill hardened steels (e.g., tool dies).
Coatings like TiN or TiAlN extend lifespan in high-heat scenarios, such as CNC machining centers running 24/7.
Drill bit for tiles and glass
Feature diamond-shaped tungsten carbide tips with pilot points to prevent slipping. Use low RPM without hammer action—ideal for bathroom tile installations or aquarium glass drilling. Pro tip: A standard masonry bit can work on ceramics if you’re careful, but expect slower progress.
Drill bit for wood
Designed for clean holes with minimal splintering:
Twist bits (up to 20mm) for thick lumber in furniture making.
Spade bits (13mm+) for rough carpentry like deck building.
Forstner bits create flat-bottom holes for concealed cabinet hinges.
Dowel bits ensure precision in joinery workshops.
Drill bit for non-ferrous metals and composite materials
For carbon fiber (CFRP), fiberglass (GFRP), or graphite:
PCD drill bits with synthetic diamond edges prevent delamination in aerospace wing assembly.
CVD-coated bits handle abrasive composites in wind turbine blade production.
Drill Bit Types Explained
Drill bits can also be categorized by their hole-making functions or applications. Each type typically suits specific materials. The most common types include:
Auger drill bits
Used for drilling deep holes in thick lumber, beams, or logs. Compared to standard wood bits, auger bits have longer bodies with deep spiral flutes for efficient chip removal. The self-feeding screw tip maintains drilling alignment—perfect for timber framing or shipbuilding tasks requiring precision in dense wood.
Brad point drill bits
Designed for accurate woodworking. The brad point tip prevents skidding, while dual flutes clear chips smoothly. Some models include a depth stop collar (e.g., for repetitive shelf pin holes in cabinetmaking). Ideal for dowel joint drilling in furniture workshops.
Countersink drill bits
Create flush screw seating by drilling conical recesses. Removes burrs in wood, metal, or plastics. SUNDI’s PCD countersink bits handle abrasive composites like carbon fiber aircraft panels without edge chipping.
Flat drill bits
Drill large holes (13mm+) in wood. The flat head with center spur ensures precise starting points. Simple design, cost-effective for rough carpentry (e.g., door lock installations in construction sites).
Forstner drill bits
Specialized for flat-bottom holes in cabinetry. The perimeter cutting edge minimizes tear-out, while the center spur guides clean cuts. Essential for concealed hinge mounting in kitchen cabinet factories.
Hinge drill bits
Similar to Forstner bits but optimized for hinge alignment. Ensures screw holes stay centered—critical for door hardware installations to prevent misalignment in high-end joinery.
HSS drill bits
Made from high-speed steel (HSS). Handles wood, plastics, and soft metals (e.g., copper tubing). Affordable and versatile—upgrade with TiN/TiAlN coatings for extended lifespan in DIY garage projects.
Mortise drill bits
Used for square/rectangular mortises in woodworking. Combines an inner drill bit and outer chisel, requiring a mortising machine. Key for traditional joinery like table leg assemblies in woodcraft studios.
Deep Hole Drill Bits（Gun drill）
Specialized for deep-hole drilling (depth-to-diameter ratio ≥10:1), like hydraulic valve bodies or mold cooling channels. Its slender rod structure with internal coolant channels enables stable drilling beyond 1-meter depths, achieving smooth finishes (Ra ≤1.6μm) critical for aerospace fuel injection systems or hydraulic cylinder manufacturing.
Indexable Drill Bit
Designed for heavy-duty cutting and large-diameter holes (typically ≥12mm), such as flange holes or shaft components. Features a short, rigid body with replaceable carbide inserts. The U-shaped insert pocket allows quick blade changes, making it adaptable for through-holes, blind holes, and cost-effective bulk machining (e.g., batch processing engine blocks in automotive plants).
Step drill bits
Feature tapered step design for multiple hole sizes in one bit. Ideal for thin metals (e.g., electrical enclosures) or PVC pipes—plumbers use these to quickly adjust hole diameters on-site.
Drill Shank Types Explained
The shank type of a drill bit must match the drill chuck for secure operation. Below are common shank designs:
Hex shank
Features a hexagonal shape that locks tightly into chucks, minimizing slippage. Primarily used with hammer-mode electric screwdrivers or impact drivers for high-torque applications.
SDS shank
Specifically designed for rotary hammer drills and hammer drills. Instead of relying on chuck clamping force, it uses grooves to lock into the tool. Ideal for heavy-duty drilling in concrete or masonry.
Straight shank
The most common type, with a cylindrical shape. Requires a chuck or collet to secure it. Versatile for use in cordless drills, bench drill presses, CNC machines, and milling machines.
Threaded shank
Equipped with threads for manual tightening. Eliminates the need for a traditional chuck, making it suitable for tight spaces and high-torque drilling where slippage must be avoided (e.g., metal fabrication or automotive repair).
Drill Bit Angles Explained
The angle of a drill bit directly affects drilling efficiency and its suitability for different materials. Drill bits mainly have two common point angles: 118° and 135°.
A 118° drill bit is the standard angle, suitable for general-purpose drilling in metals (e.g., mild steel), wood, and plastics.
A 135° drill bit is better for harder materials such as stainless steel, hardened steel, high-strength alloys, and titanium alloys.
Metal drill bits can also have other angles (e.g., 80°, 90°, 120°, 140°). Smaller drill point angles (e.g., 80°–90°) are sharper and work well for softer materials, while larger angles (e.g., 135°–140°) are more durable for harder materials. However, larger angles increase cutting resistance because the flatter tip reduces sharpness.
Conclusion
Selecting the proper drill bit is critical for both material compatibility and operational efficiency. For instance, when working with hardened steel, a cobalt-coated bit resists wear far better than standard options—directly extending tool lifespan. SUNDI’s engineers specialize in matching drill geometries to unique applications, whether it’s aerospace-grade titanium or high-volume woodworking. Case studies show clients reducing tool replacement costs by 22% after adopting our customized solutions. To discuss your specific machining challenges, reach out to our technical team for a free consultation.
FAQ
Q1: Can I use a wood bit on metal?
Wood bits lack the helix angle and hardness for metal. Attempting this will dull the edge instantly.
Q2: Why do bits overheat in CNC machines?
Cause: Incorrect RPM (too high) or poor coolant flow.
Fix: Use this formula: RPM = (Cutting Speed x 318)/Drill Diameter.
Q3: Should I use a PCD drill or a CVD-coated drill?
A: Choose based on your material and priorities:
Pick CVD-Coated Drills if:
Drilling composites (e.g., aerospace parts) to prevent exit-hole delamination.
Prioritizing lower upfront cost or short-term projects.
Pick PCD Drills if:
Drilling metal-composite stacks (e.g., CFRP + aluminum) with metal exit layers.
Needing longer tool life, stable hole quality in high-volume jobs, or reusable tools.
Quick Rule:
Anti-delamination → CVD | Durability/metal stacks → PCD.
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