Magnetic Drill Bits

Magnetic drill bits, often known simply as mag drill bits, are high-performance tools specifically designed for use with a magnetic drill press or mag base drill bits machine. These tools, which typically take the form of an annular cutter, are superior to conventional twist drills for boring large diameter holes in ferrous metals.

They operate by cutting only the perimeter of the hole, leaving a solid core (or slug). This significantly reduces the cutting resistance required, making the job quicker, safer, and much more efficient.

How Magnetic Drill Bits Work

Magnetic drill bits operate on a principle of focused, peripheral cutting. Unlike traditional drills that shear and scrape away the entire material across the hole's diameter, the annular cutter removes material in a thin ring.

The mag drill bit is hollow. As it rotates and penetrates the material, the multiple cutting edges around its circumference bore a precise, clean hole. The material inside the cutting ring is ejected as a solid piece, or "slug," upon breakthrough. This method requires less horsepower and thrust, vastly extending the life of the drill bit and delivering a superior finish. They are sometimes referred to as broach cutters because of this design.

Magnetic Drill Bits Types

Magnetic drill bits are categorised based on the material they are made from, the mechanism used to connect them to the drill, and their specific function.

By Material

• High-Speed Steel (HSS): The standard choice for general-purpose drilling in mild and structural steel. HSS annular cutters offer excellent value and can be re-sharpened.
• Tungsten Carbide Tipped (TCT): Designed for extreme durability and hardness. TCT mag drill bits are ideal for cutting tougher materials, such as stainless steel and hardened alloys, offering a longer lifespan and faster cutting speed.

By Shank

• Weldon Shank: The most common shank design, featuring two or three flats for secure clamping.
• Quick-Change Shank: Designed for tool-less installation and removal, providing rapid swapping of magnetic drill bits on site.

By Size

• Various Diameters and Depths: Magnetic drill bits set products are available in a wide range of diameters (from 12mm up to 100mm, including popular sizes like the 40mm mag drill bit) and cutting depths (short, long, and deep hole cutters).

By Function

• Standard Annular Cutter: The primary style of bits for magnetic drill machines, optimised for general hole boring.
• Deep Hole Cutter/Broach Cutter: Extended length annular cutters for drilling through exceptionally thick materials.

Applications of Magnetic Drill Bits

Magnetic drill bits are indispensable tools engineered for efficient drilling across a variety of materials, especially in metalworking and construction tasks. Below are some examples of their applications:

Structural Steel Fabrication and Bridge Building

Mag drill bits are essential for fabricating large metal frameworks. They are used to quickly and precisely bore holes for bolts and rivets in structural steel beams, columns, and plate sections. Their accuracy and portability are critical for construction projects like bridge building, high-rise towers, and large industrial facilities where precision on thick materials is non-negotiable.

Heavy Plant Maintenance

In maintenance workshops and on site, magnet drill bits are critical for repairing large machinery, vehicles, and industrial equipment. Their portability means that instead of moving a heavy, unwieldy component to a stationary drill press, the magnetic base can be affixed directly to the workpiece. This makes on-site repair, modification, and maintenance of heavy plant equipment efficient and safe.

Electrical Installation (Boring Panel Boxes)

Electricians utilise drill press bits mounted on magnetic bases to quickly bore clean, accurate holes in thick metal enclosures and panel boxes. This is vital during large-scale electrical installations for running cable glands, conduit, and mounting control switches, ensuring precise fit-up without burrs.

General Workshop Drilling

In general metalworking, using bits for magnetic drill machines on metal sheets and frames provides superior hole quality and speed compared to conventional bench drills. This method is highly valued in fabrication shops for consistently tackling large diameters and batch work with high efficiency.

How to Choose the Right Magnetic Drill Bits

Selecting the correct magnetic drill bit is crucial for safety, maximising efficiency, and achieving the required hole quality. Buyers should evaluate the following factors based on their application and equipment:

Workpiece Material (Hardness) vs. Cutter Material (HSS vs. TCT)

The material being drilled is the primary driver of cutter selection. For mild steel and general fabrication, High-Speed Steel (HSS) mag drill bits are cost-effective. For tougher materials, such as stainless steel or very hard alloys, you must use Tungsten Carbide Tipped (TCT) annular cutters, as their superior hardness and heat resistance prevent premature wear and failure.

Required Hole Diameter and Depth

Ensure the magnetic drill bit meets both the diameter requirement (e.g., a 40mm mag drill bit) and the required depth. The cutter's depth must always be slightly greater than the thickness of the material to ensure a clean slug ejection.

Drill Press Power (HP/Torque) Compatibility

The magnetic drill press being used must have adequate horsepower and torque to handle the chosen cutter size and material. Using a large diameter TCT cutter on an underpowered machine will lead to slow cutting and potential tool stalling, stressing both the cutter and the machine.

Shank Type (Weldon vs. Quick-Change)

The Weldon shank is the industry standard, offering a robust, secure connection ideal for heavy-duty torque. Quick-Change shanks are preferred in environments requiring frequent cutter swaps, as they dramatically reduce setup time and labour.

RS Australia Is Your Trusted Partner for Magnetic Drill Bits

As a leading supplier and distributor, RS Australia is your trusted partner for a vast range of high-quality magnetic drill bits. We stock thousands of products from global brands like Sutton Tools, Rotabroach and our very own RS PRO, ensuring you find the right component for any job.

Our user-friendly website makes it easy to search, compare, and order other essential tools like hole saw drill bits and end mill drill bits. RS Australia offers fast delivery of our full range of products. For more details on delivery services and fees, please refer to our Delivery page.