Mag Drill Bits & Accessories

About Mag Drill Bits & Accessories

Magnetic drilling, also known as mag drilling, represents one of the most efficient methods for creating large diameter holes in steel and other ferrous metals. Whether working on structural steelwork, fabrication projects, or site installation work, mag drill bits and their associated accessories are essential tools for achieving accurate, burr-free holes in demanding applications. The magnetic base of these specialist drills creates a powerful bond with the workpiece, providing stability and precision that conventional drilling simply cannot match when working with thick metal sections.

Tooled-Up.com stocks a comprehensive range of magnetic drill bits designed specifically for use with mag drills from leading manufacturers including Milwaukee, DeWalt, Makita, and Fein. These annular cutters - as they're technically known - cut only the periphery of the hole rather than removing all the material, making them significantly faster and more efficient than traditional twist drills for large diameter holes. The range includes various cutting depths, diameters, and coatings to suit different materials and applications, alongside essential accessories such as pilot pins, arbors, cutting fluid, and replacement parts.

The complete mag drill system relies on quality accessories working in harmony with precision cutters. From the pilot pin that centres and stabilises the cut, to the arbor that secures the cutter to the drill, each component plays a vital role in achieving professional results. Proper maintenance accessories, including cutting lubricants and cleaning supplies, ensure longevity and consistent performance across hundreds of holes. Understanding the full ecosystem of mag drill bits and accessories available at Tooled-Up helps tradespeople select the right components for their specific metalworking requirements.

Jargon Buster

• Annular Cutter: The correct technical term for a mag drill bit. Unlike conventional twist drills that remove all material, annular cutters have cutting teeth only on the periphery, removing a ring of material and leaving a solid slug, resulting in faster cutting and less power consumption.
• Pilot Pin: A spring-loaded pin that sits in the centre of the annular cutter, providing initial location and stability during the cutting process. The pilot pin also ejects the metal slug once the cut is complete.
• Arbor (or Cutter Arbor): The adaptor shaft that connects the annular cutter to the magnetic drill's chuck. Available in different shank sizes (typically 19mm or 3/4" Weldon shank) to suit various mag drill models.
• Cutting Depth: The maximum thickness of material that an annular cutter can drill through in a single pass, typically ranging from 25mm to 110mm depending on the cutter specification.
• TCT (Tungsten Carbide Tipped): Premium annular cutters with carbide tips that offer superior performance in hard materials and significantly longer tool life compared to standard HSS cutters.
• Weldon Shank: The flat-sided shank design found on mag drill cutters and arbors, featuring a flat surface that allows secure gripping with a set screw to prevent slippage under high torque.

Who Uses Mag Drill Bits & Accessories?

• Structural Steel Erectors: For drilling connection holes in beams, columns, and steel frameworks on construction sites
• Fabricators and Welders: Creating precise holes in steel plate, box section, and metal components in workshop environments
• Mechanical and Electrical Engineers: Installing cable penetrations, mounting brackets, and fixings in metal enclosures and machinery
• Shipbuilders and Marine Engineers: Drilling through thick steel plate in vessel construction and repair work
• Railway and Infrastructure Contractors: Creating fixing points in rails, girders, and bridge components
• HVAC Installers: Making large diameter holes for ductwork penetrations through steel structures
• Maintenance Engineers: Retrofitting fixings and modifications to existing steel structures in industrial facilities
• Metalworking Workshops: General fabrication work requiring clean, accurate large diameter holes

How to Choose the Right Mag Drill Bits & Accessories

Cutter Diameter: Select the diameter based on your specific hole requirements, typically ranging from 12mm up to 100mm or more. Consider the most common hole sizes in your work - M12, M16, and M20 bolt clearance holes are particularly common in structural steelwork. Larger diameter cutters require more powerful mag drills with adequate motor capacity.

Cutting Depth Required: Match the cutter's cutting depth to your material thickness. Standard cutters typically offer 25mm, 35mm, or 50mm depth of cut, whilst specialist long-series cutters provide 75mm or 110mm for thick plate work. Always allow slight clearance beyond your material thickness for breakthrough.

Material and Coating: High-Speed Steel (HSS) cutters suit general mild steel applications and offer excellent value. For harder materials, stainless steel, or extended tool life, TCT (Tungsten Carbide Tipped) cutters justify their higher cost through longevity and performance. TiN (Titanium Nitride) and TiAlN coatings further enhance wear resistance and reduce friction.

Shank Compatibility: Ensure your arbor and cutters match your mag drill's specifications. The 19mm (3/4") Weldon shank is most common, but verify compatibility. Universal quick-change systems from brands like Milwaukee and Fein may require specific arbors available from the Tooled-Up range.

Pilot Pin Specification: Different cutter diameters and depths require appropriately sized pilot pins. Standard 6mm pins suit most applications, but larger cutters may need 10mm pins for adequate support. Always keep spare pilot pins - they're consumable items that wear with use.

Quality and Brand: Professional-grade cutters from Milwaukee, Fein, or specialist manufacturers like Broach Cutters deliver superior performance and value over cheap alternatives. The initial investment is quickly recovered through faster cutting, cleaner holes, and extended tool life, particularly important for high-volume work.

Popular Accessories

• Replacement Pilot Pins: Essential consumables in various diameters (6mm, 10mm) and lengths to suit different cutter specifications
• Cutter Arbors: Spare or additional arbors with different shank sizes for multiple mag drill compatibility
• Cutting Fluid and Lubricants: Specialised mag drill cutting paste reduces friction, extends cutter life, and improves hole quality
• Magnetic Drill Stands and Extensions: Increase versatility and reach when drilling in awkward positions
• Centering Guides: Ensure accurate hole placement, particularly useful for template or pattern drilling
• Cutter Storage Cases: Organised storage protects expensive cutters from damage and contamination
• Replacement Magnets: Magnet sections for older or damaged drill bases
• Swarf Brushes and Cleaning Tools: Maintain cutter teeth and pilot pin mechanisms for optimal performance
• 240v Extension Leads: Heavy-duty rated leads for site work where power access is limited
• Deburring Tools: Remove sharp edges from drilled holes for safe handling and proper fitment

Safety Information

Magnetic Base Security: Always verify the magnetic base has achieved full contact and secure adhesion before commencing drilling operations. Test the hold by attempting to move the drill - it should be completely immobile. Clean both the mag drill base and workpiece of paint, rust, scale, or debris that could compromise magnetic grip. Minimum material thickness recommendations must be observed, typically 10mm for safe magnetic adhesion.

Personal Protective Equipment: Safety glasses or face shields are mandatory when mag drilling to protect against hot metal swarf and cutting debris. Heat-resistant gloves protect hands when handling freshly cut slugs, which can reach temperatures exceeding 100°C. Hearing protection is advisable in enclosed spaces or when operating multiple drills. Steel toecap boots protect against dropped cutters or falling equipment.

Electrical Safety: Ensure 240v mag drills are supplied through properly rated circuit protection. RCD (Residual Current Device) protection is essential on construction sites and complies with HSE guidance. Inspect cables and plugs before use for damage, and never operate mag drills in wet conditions unless specifically rated for such use. Position cables safely to prevent trip hazards or damage from swarf.

Cutter Handling and Installation: Mag drill cutters have extremely sharp teeth - handle with appropriate care and use gloves during installation. Ensure cutters are properly secured in the arbor with the grub screw tightened onto the Weldon flat. Check pilot pin spring action before use and replace worn or damaged pins immediately. Never operate a mag drill without a properly functioning pilot pin installed.

Operation and Maintenance: Use appropriate cutting speeds and feed rates as recommended by the cutter manufacturer - forcing the cut risks cutter breakage and personal injury. Apply cutting lubricant consistently throughout the operation to prevent cutter overheating and potential failure. Allow the drill motor to reach full speed before engaging the cut, and maintain steady, even pressure. Remove the cutter from the hole periodically to clear swarf on deeper cuts.

Frequently Asked Questions

What's the difference between HSS and TCT mag drill bits?

High-Speed Steel (HSS) cutters are suitable for drilling mild steel and general metalworking applications, offering good performance at an economical price point. TCT (Tungsten Carbide Tipped) cutters feature carbide inserts on the cutting teeth, providing significantly longer tool life - often 10-20 times that of HSS in demanding applications. TCT cutters excel in harder materials like stainless steel, tool steel, and cast iron, and maintain sharper cutting edges over extended use. For high-volume work or tough materials, TCT cutters offer better value despite higher initial cost.

How often should I replace pilot pins?

Pilot pins are consumable items that gradually wear through use. Replace pilot pins when you notice reduced centring accuracy, difficulty ejecting slugs, or visible wear on the pin tip. Professional operators drilling dozens of holes daily might replace pilot pins weekly, whilst occasional users may achieve months of service. Keep spare pins readily available - a worn pilot pin can cause cutter wander, oversize holes, and premature cutter failure. The modest cost of replacement pins is insignificant compared to the expense of damaged cutters or rejected work.

Can I use mag drill bits in a normal pillar drill?

Annular cutters are specifically designed for mag drills and are not suitable for use in conventional pillar drills or drill presses. The cutting geometry, speeds, and feed rates differ significantly. Mag drills operate at lower RPMs (typically 200-600 RPM) with high torque and rigid support, whilst pillar drills run at higher speeds unsuited to annular cutters. Additionally, the pilot pin mechanism and slug ejection system require the specific setup of a magnetic drill. For pillar drill work, use conventional twist drills or hole saws designed for that application.

Why do I need cutting fluid when using a mag drill?

Cutting fluid serves multiple critical functions in mag drilling operations. It lubricates the cutting teeth, reducing friction and heat generation that would otherwise dramatically shorten cutter life. The cooling effect prevents work hardening of the material being cut, which makes subsequent cutting progressively more difficult. Lubrication also improves surface finish and hole accuracy whilst helping to clear swarf from the cutting zone. On thicker materials or harder steels, cutting fluid can double or triple cutter lifespan. Even a basic cutting paste represents excellent value compared to premature cutter replacement costs.

What size holes can magnetic drill bits cut?

The range of mag drill bits available at Tooled-Up extends from small 12mm diameter cutters up to 100mm or larger for specialist applications. The practical limit depends on your mag drill's motor power and magnetic holding force - larger cutters demand more torque and generate greater side loads. Common sizes for structural steelwork include 13mm, 17mm, and 22mm for standard bolt clearance holes. Industrial fabrication may require anything from 25mm to 60mm for pipework penetrations and cable entries. Always verify your specific mag drill's maximum recommended cutter diameter in the manufacturer's specifications to ensure safe operation and avoid overloading the motor or compromising magnetic grip.