Cone & Stepped Drill Bits

About Cone & Stepped Drill Bits

Cone and stepped drill bits are specialised cutting tools designed to drill multiple hole sizes with a single bit, making them essential equipment for electricians, plumbers, HVAC engineers and sheet metal workers. Unlike conventional twist drills that create just one diameter hole, stepped drill bits feature a conical or pyramid shape with multiple cutting edges at graduated diameters. This innovative design allows tradespeople to drill and enlarge holes progressively in thin materials such as sheet metal, plastic, aluminium and copper without the need to constantly change bits.

Our comprehensive range includes over 45 products from leading manufacturers including Bosch, Sealey, Makita, Milwaukee and Faithfull. You'll find individual stepped bits in various size ranges, as well as convenient 3-piece sets that cover the most common drilling requirements on site. Many bits feature premium coatings such as titanium nitride (TiN) or aluminium titanium nitride (AlTiN) which significantly extend tool life and improve cutting performance. Whether you're drilling cable entry holes in electrical enclosures, creating mounting points in ventilation ducting, or enlarging pilot holes in metal fabrication work, stepped drill bits deliver clean, burr-free holes with exceptional accuracy.

The hexagonal shank design found on most modern stepped bits ensures a secure grip in both cordless drills and impact drivers, preventing slippage during use. High-speed steel (HSS) construction provides the hardness and heat resistance necessary for cutting through tough materials, whilst the self-centering tip design eliminates the need for pilot holes in most applications. With step increments typically ranging from 2mm to 4mm, these versatile tools can create holes from as small as 4mm up to 32mm or larger, all from a single bit.

Jargon Buster

• HSS (High-Speed Steel): A hardened steel alloy specifically designed to withstand the high temperatures generated during drilling. HSS stepped bits maintain their cutting edge even when working at speed through sheet metal and other materials.
• TiN Coating (Titanium Nitride): A gold-coloured surface treatment that increases hardness, reduces friction and extends bit life by up to three times compared to uncoated HSS. The coating also helps prevent material adhesion during drilling.
• AlTiN Coating (Aluminium Titanium Nitride): An advanced dark grey coating that offers superior heat resistance and hardness compared to standard TiN. Ideal for demanding professional applications and drilling harder materials.
• Step Increment: The diameter difference between each stepped level on the bit, typically 2mm, 3mm or 4mm. Smaller increments provide more size options but require more steps to reach larger diameters.
• Cone Cutter: A conically-shaped drill bit without distinct steps, designed for enlarging existing holes or creating tapered openings. Often used for deburring and chamfering applications.
• Hex Shank: A six-sided shaft design (typically ¼" or ?") that prevents slippage in drill chucks and is compatible with quick-change bit holders and impact drivers.

Who Uses Cone & Stepped Drill Bits?

• Electricians and Electrical Engineers: Creating cable entry points in consumer units, junction boxes and electrical enclosures
• Plumbers and Heating Engineers: Drilling holes for pipe work, radiator valves and mounting brackets in sheet metal
• HVAC and Air Conditioning Installers: Making ductwork connections and mounting holes in ventilation systems
• Metal Fabricators and Sheet Metal Workers: Precision hole drilling and enlarging in steel, aluminium and copper sheet
• Automotive Technicians and Vehicle Modifiers: Custom installations, bodywork modifications and electrical system upgrades
• Shop Fitters and Signage Installers: Mounting point creation in various thin materials including plastics and composite panels
• General Builders and Maintenance Engineers: Versatile hole drilling across multiple site applications and materials
• DIY Enthusiasts: Home improvement projects requiring clean, accurate holes in sheet materials

How to Choose the Right Cone & Stepped Drill Bits

Material and Coating: Standard HSS bits suit occasional use and softer materials, whilst titanium-coated options (TiN or AlTiN) from manufacturers like Bosch and Milwaukee offer significantly extended lifespan for professional tradespeople. The coating reduces friction and heat build-up, particularly important when drilling stainless steel or harder alloys.

Size Range Requirements: Consider the hole diameters you commonly need. Starter sets typically cover 4-12mm, 6-20mm and 10-32mm ranges. If you regularly work with specific sizes, individual bits from brands like Sealey or Faithfull may prove more economical than sets containing unused sizes.

Step Increments: Smaller step increments (2mm) provide more sizing options but take longer to reach larger diameters. Larger increments (4mm) work faster but offer fewer intermediate sizes. Match the increment to your typical precision requirements.

Shank Type: Hex shanks are now standard and work perfectly with modern cordless drills and impact drivers. Ensure compatibility with your existing equipment, particularly quick-change systems from Makita, Milwaukee or DeWalt.

Material Thickness Capability: Most stepped bits work optimally in materials up to 3-4mm thick. Check the manufacturer's specifications if you regularly work with thicker sheet metal or need to stack multiple sheets.

Single Bits vs Sets: Three-piece sets from Bosch, BlueSpot or Draper offer excellent value and cover the most common requirements for around £30-60. Professional tradespeople drilling hundreds of holes weekly should invest in premium coated sets for durability.

Popular Accessories

• Cutting Fluid and Lubricants: Extend bit life and improve cutting performance, especially in stainless steel and harder materials
• Centre Punches: Create accurate starting points on unmarked materials, preventing bit wander
• Quick-Change Bit Holders: Enable rapid bit changes and work seamlessly with hex shank stepped bits
• Cordless Drill/Drivers: Essential power source, with 18V models from Makita, Milwaukee or DeWalt providing optimal performance
• Deburring Tools: Remove sharp edges and burrs from freshly drilled holes for safe, professional results
• Measuring and Marking Tools: Digital callipers and scribe sets ensure accurate hole positioning and sizing
• Safety Glasses and Work Gloves: Essential PPE when drilling metal produces hot swarf and sharp edges
• Storage Cases and Tool Rolls: Protect bits from damage and keep sets organised on site

Safety Information

Personal Protective Equipment: Always wear safety glasses or a face shield when drilling metal, as hot metal swarf can cause serious eye injuries. Work gloves protect against sharp edges and hot materials, whilst ear protection is advisable when using impact drivers or working in enclosed spaces.

Secure Workpieces: Always clamp or securely fix sheet material before drilling. Stepped bits can grab suddenly when breaking through, potentially spinning loose material dangerously. Never hold work by hand whilst drilling.

Speed Settings: Use moderate drill speeds (500-1000 RPM for most applications) to prevent overheating and premature bit wear. Excessive speed generates heat that can damage coatings and temper the cutting edges. Consult HSE guidance on safe operation of portable power tools.

Material Considerations: Ensure your work area is clear of flammable materials when drilling metal, as friction can produce sparks. Be aware of what lies behind the material you're drilling – check for electrical cables, gas pipes or other services before commencing work.

Bit Condition: Inspect bits before use for damage, wear or coating deterioration. Damaged bits can shatter under load or produce rough, dangerous holes. Replace worn bits promptly rather than forcing them to continue cutting.

Frequently Asked Questions

What's the difference between cone cutters and stepped drill bits?
Stepped drill bits feature distinct flat platforms at each diameter increment, allowing you to drill precise, specific hole sizes. Cone cutters have a smooth conical profile without defined steps, making them ideal for deburring, chamfering or creating tapered holes rather than specific diameters. Stepped bits are more versatile for most trades applications.

Can I use stepped drill bits in a cordless impact driver?
Yes, hex shank stepped bits work excellently in impact drivers, particularly when drilling harder materials like stainless steel. The percussive action can actually improve cutting performance and reduce binding. However, use lower speed settings and ensure your impact driver has adequate torque (typically 150Nm+ for larger holes).

Why do my stepped bits keep breaking or wearing quickly?
Premature failure usually results from excessive speed, insufficient lubrication or attempting to drill materials that are too thick or hard. Most stepped bits are designed for sheet materials up to 3-4mm thick. Ensure you're using appropriate cutting fluid, moderate speeds (not maximum RPM), and that you allow the bit to cut rather than forcing it through the material.

Do I need different bits for stainless steel versus mild steel?
Whilst standard HSS bits can drill both materials, coated bits (TiN or AlTiN) significantly improve performance in stainless steel, which work-hardens during cutting. Use slower speeds, apply steady pressure, and always use cutting fluid when working with stainless. Premium brands like Bosch and Milwaukee offer specialist coatings specifically for stainless steel applications.

How do I know which step size I've drilled to?
Each step on quality bits is marked with its diameter in millimetres. Simply drill until your desired size marking is flush with the material surface. For precision work, use the bit to create a slightly undersized hole, then verify with callipers before enlarging to the final dimension. This technique prevents oversizing holes that cannot be corrected.