The invention of the magnetic drill brought great convenience to the metal-cutting process. When the operating environment becomes complex, magnetic drills are superior to large drilling machines thanks to their portability and magnetism. Annular cutters are drill bits mounted on magnetic drills, so they are also called magnetic drill bits. In this article, we will provide a complete guide to annular cutters. Read on to understand everything about annular cutters.

What is an annular cutter?

Annular cutters, also called mag drill bits, core cutters, rota-broach cutters, or broach cutters, are metalworking tools used in creating holes. The term “annular cutter” is named after the annulus shape and the term “mag drill bit” is named after the machine it uses – a magnetic drill. An annular cutter only cuts the outline of the hole and leaves a slug that is removed. Compared to other hole-making tools like twist drills and hole saws, annular cutters are more efficient because they cut less material in the cutting process. Usually, there are two types of annular cutters: high-speed steel (HSS) and tungsten carbide tipped (TCT). Weldon shanks and universal shanks are the most common shank types of mag drill bits.

Today, we’ll explain the detail of the annular cutter. After reading this article, we believe you’ll have a thorough understanding of this hole-making tool.

What is a magnetic drill?

Since a mag drill bit is used with a magnetic drill, here is a brief introduction to this machine. A magnetic drill is a portable electric drilling machine designed to create holes in metal. Unlike other drilling machines, a magnetic drill is equipped with a magnetic base which enables the drill to be adsorbed onto the metallic workpiece during operation. Apart from annular cutters, magnetic drills can also use with various tools like reamers and countersinks.

Applications of annular cutters

The versatility of annular cutters allows them to cut various materials, including stainless steel, structural steel, cast iron, carbon steel, high-tensile steel, and more. Any industry that needs to create holes in metal can use a mag drill bit, including, oil & gas, construction, metal fabrication, and more. In addition to industrial projects, annular cutters can be used in DIY workshops.

Types of annular cutters

According to the manufacturing material, there are two types of mag drill bits: high-speed steel (HSS) bits and tungsten carbide tipped (TCT) bits.

1. High-speed steel (HSS)

HSS annular cutters are made completely from high-speed steel. They are less expensive than TCT mag drill bits and are less likely to break during operation. HSS bits are suitable for cutting softer metal like aluminum. One of the greatest advantages of HSS mag drill bits is that they can be resharpened.

2. Tungsten carbide tipped (TCT)

TCT mag drill bits are equipped with tungsten carbide tips, thus being ideal for drilling harder materials. As we know, tungsten carbide is the second hardest material, featuring excellent durability and strength. So, TCT annular cutters have longer service life than HSS cutters. However, tungsten carbide can break more easily and TCT mag drill bits can not be re-sharpened.

Shank types

Shanks of annular cutters can be different. The most commonly used shanks are Weldon shanks and Universal shanks. In addition, there are Fein quick-IN shank, threaded shank, and Parallel shank.

1. Weldon shanks

Annular cutters with the Weldon shank have two flats on the shank for holding the cutters. The Weldon shank is a traditional technology that is widely used in drilling applications. With a Weldon shank, the cutter can be rigidly held by the machine, creating burr-free holes.

2. Universal shanks (Nitto shanks)

Mag drill bits with the Universal shank or Nitto shank feature one flat and three grooves for quick connection. Thanks to this design, the cutter is free from the strain of grub screws. In most cases, Universal shank cutters can be used in Weldon shank machines, but if you want to use Weldon shank mag drill bits in “one touch” machines, an adaptor is required. Since there is only one flat, Universal shank annular cutters won’t be securely held by the machines.

Pilot pins

A pilot pin, also called a center pin, is designed for several purposes.

1. Help the annular cutter find the center mark, ensuring that the cutter is drilling in the right position and path.
2. The flow of internal lubrication is controlled by the pilot pin.
3. After the hole is finished, the pilot pin helps to remove the slug.

Why use annular cutters (Advantages)?

There are various types of drills we can choose from. But why annular cutters?

1. Efficiency

Because an annular cutter only cuts the outline of a hole, it can cut almost 4 times faster than traditional drill bits like twist drills or hole saws. In addition, you can create a hole in one shot with a mag drill bit, with no pre-drilling and step-drilling required.

2. Power saving

Unlike hole saws, mag drill bits require less power to operate due to their design. Instead of drilling through the whole workpiece, the cutters only focus on the outline, thus requiring less energy during operation.

3. Longer service life

Several cutting edges cut the workpiece simultaneously, so annular cutters are less likely to wear quickly. In addition, HSS and tungsten carbide are extremely durable wear-resistant materials, ensuring the longer service life of mag drill bits.

4. Burr-free

Due to the design of the teeth, annular cutters create fewer chips and can evacuate the chips during operation, leaving burr-free holes in the workpiece.

5. Accuracy

Mag drill bits can create accurate and clean holes by using a pilot pin. It is of great importance to drill holes accurately in applications like pipping.

Disadvantages

In some situations, annular cutters may not perform as well as we expect.

1. Mag drill bits are designed to drill through holes instead of blind holes. If you plan to make blind holes, you have to turn to other drills like twist drills.
2. Once an annular cutter is stuck, it is very difficult to remove it because it is almost clamped by the workpiece.

Annular cutters vs twist drills

Traditional twist drills only have two cutting edges, so they require more force and a slower feed rate to finish the cutting performance. If you plan to drill a hole larger than 1/2 inch, annular cutters should be your choice, because twist drills are ideal for smaller holes.

Annular cutters vs hole saws

Hole saws are designed for cutting wood, plastic, and thin materials. However, annular cutters are suitable for drilling larger and deeper holes in metal. In addition, annular cutters can create clean and precise holes, but holes drilled by hole saws are rough and require further deburring. When working with a thicker workpiece, annular cutters can drill faster and more efficiently with less force.

Konetool is a reliable supplier of annular cutters.

We can provide both HSS and TCT annular cutters in various sizes. In addition, annular cutter sets are also available. We have solid experience in the supply of annular cutters for clients across the world. If you’re looking for a reputable supplier of annular cutters for your business, please contact us today! Our salespeople are ready to help you!