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 create holes using cutting geometries matched to the material and machine. Some masonry systems add percussion. Shanks, flutes, and cutting tips vary by design; not every drill shares the following twist-drill features.
Shank
The shank is the rear part inserted into the drill chuck for fixation.
Flutes provide space for chip removal. They may be helical or straight, and coolant may be supplied externally or through internal passages. Not every flute extends to the shank.
A conventional twist-drill point has cutting lips and a chisel edge. Other drill types use different geometries, and a chisel edge alone does not guarantee self-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 grade-dependent alloying elements such as tungsten,
molybdenum, chromium, and vanadium. Suitable designs can machine a range of steels and non-ferrous metals as well as some nonmetals; HSS is not limited to soft metals. - Cobalt (5–8% Co) commonly refers to cobalt-alloyed HSS, not a separate pure-cobalt drill material. It may suit selected stainless steels or other demanding materials when grade, geometry, hardness, and cutting conditions are appropriate.
- Tungsten Carbide offers high hardness and wear resistance in suitable designs. The original HRA 90–94 range is not a universal specification. Hardened steel, ceramics, and glass-fibre composites require different application-qualified tools and setups.
- 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)
provides diamond cutting edges for suitable abrasive non-ferrous materials and composites. Match the tool to the actual material and process; it is not universally the best choice.
Drill bit coatings:
- Titanium Nitride (TiN)
can support wear resistance in suitable drilling applications. Its effect on tool life depends on substrate, workpiece, geometry, and cutting conditions. - Titanium Aluminum Nitride (TiAlN)
is a coating used in selected demanding cutting applications. Verify the specific coating and tool for the material and cutting conditions; the coating name alone does not establish suitability. - CVD Diamond Coating can provide wear resistance for selected abrasive non-ferrous materials and composites. The original 99% purity claim requires a coating specification; purity alone does not establish tool performance.
- Black Oxide is a surface treatment whose application depends on the tool specification. Check material compatibility with the supplier; do not apply a universal ban on aluminium solely from the treatment name.
You may have heard of PCD and SDS drill bits. Let’s clarify what they are:
PCD Drill Bits
PCD drill bits use diamond cutting edges for suitable non-ferrous materials and composites. Applications may include selected aluminium alloys, graphite, and carbon-fibre components. Suitability for aerospace parts or lithium battery pack manufacturing depends on the actual material, tool design, and process.
SDS Drill Bits
SDS identifies compatible shank and holder systems, commonly used with rotary hammers. Match the particular SDS type and operating mode to the tool and material; an ordinary clamping chuck is not an SDS holder.
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, select a masonry tool and drilling mode approved for the substrate and machine. Carbide-tipped masonry drills do not all have HSS bodies, and the tip does not automatically prevent cracking, noise, or dust. Follow installation requirements when drilling for anchors or HVAC systems.
Drill bit for metal
Match bit hardness to the metal:
HSS bits can machine various metals when their grade, geometry, and cutting conditions suit the application; they are not restricted to soft metals.
Cobalt bits (5–8% Co) tackle stainless steel pipes or hydraulic fittings.
Tungsten carbide bits drill selected hardened steels when rated for the actual hardness and setup. TiN or TiAlN may support wear resistance, but do not guarantee longer life in every high-temperature application.
Drill bit for tiles and glass
Use a bit specifically rated for the tile or glass and follow its RPM, cooling, and operating-mode instructions. Do not use hammer action for ordinary glass drilling or assume every ceramic tile accepts a standard masonry bit. Confirm the glass type; tempered glass is not suitable for conventional drilling.
Drill bit for wood
Designed for clean holes with minimal splintering:
Twist bits may suit timber in a range of sizes; the original 20 mm value is not a universal upper limit.
Spade bits are used for suitable woodworking holes; the original 13 mm value is not a universal minimum.
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 may suit selected composites, but diamond cutting edges alone do not prevent delamination. Geometry, support, feed, and the laminate must be considered.
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.
Countersinks form conical recesses or deburr suitable holes. Match angle and diameter to the fastener and drawing. PCD designs may suit abrasive composites, but freedom from edge chipping is not guaranteed.
Flat drill bits
Flat or spade bits drill suitable woodworking holes in a range of sizes; 13 mm is not a universal minimum. Select diameter, entry method, and cutting conditions for the tool and workpiece. They can be economical for suitable carpentry tasks.
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
The term hinge drill may refer to a self-centering drill for hinge screw holes or to a cutter for a concealed-hinge cup. These have different functions; select the design for the actual hole rather than treating every hinge drill as a Forstner bit.
HSS drill bits
HSS drills can cover a range of metals and nonmetals when designed for the application. A TiN or TiAlN coating may support wear resistance, but does not automatically increase life or replace correct tool selection.
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）
Gundrills are specialised tools for suitable deep-hole applications. A depth-to-diameter ratio around 10:1 is a common convention, not a universal threshold. The original claims of depths beyond 1 metre and Ra ≤1.6 μm require a qualified process; they are not guaranteed by internal coolant channels.
Indexable drills use replaceable cutting inserts and are available in different lengths and diameters. The original ≥12 mm description is not a universal limit, and insert pockets are not all U-shaped. Select the drill for the hole type, material, and machine.
Step drill bits
Feature tapered step design for multiple hole sizes in one bit. Ideal for thin metals (e.g., large 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
A hex shank requires a compatible chuck or holder. It does not by itself qualify a drill for an impact driver or hammer mode; verify the tool’s permitted drive and operating conditions.
SDS shank
An SDS shank uses a matching holder to retain the tool and transmit motion. Match the particular system, such as SDS-plus or SDS-max; it is not interchangeable with every hammer-drill chuck.
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
A threaded shank connects to a specified threaded holder or spindle. Match thread size, direction, and seating requirements; manual tightening alone does not establish safe retention or universal high-torque suitability.
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° point is one possible design for demanding metal drilling. It is not automatically the correct choice for every stainless steel, hardened steel, high-strength alloy, or titanium application.
Other point angles include 80°, 90°, 120°, and 140°. Selection depends on material, hole requirements, drill design, and setup. Point angle alone does not establish cutting resistance, durability, or a simple soft-material versus hard-material rule.
Conclusion
Select the drill material, geometry, coating, and cutting conditions for the application. Cobalt-alloyed HSS is not simply a cobalt coating and does not automatically suit every hardened steel. SUNDI’s engineers can help assess tool requirements; contact our technical team to discuss your machining application.