What Are Cutting Screws and How Do They Work?

Cutting screws, also called thread-cutting screws, create precise internal threads in pre-drilled holes, eliminating the need for separate tapping operations. They are a reliable solution for harder materials, including metal, plastic, and other dense surfaces where clean threads are critical. In this guide, we explore cutting screws, how they work, their types, and how to choose the best option for your needs.

What Are Cutting Screws?

Cutting screws are externally threaded fasteners that are designed to cut mating threads into a pre-drilled hole. They are different from standard machine screws, which require tapped holes.

Cutting screws fall under the broader "self-tapping" umbrella, but unlike thread-forming self-tappers, they remove material rather than displace it. This makes them distinct and better suited for harder materials. Some of the key characteristics of cutting screws include:

• Have sharp cutting edges or flutes at the tip
• Require a pilot hole
• Produce chips as material is removed
• Are often used where accuracy and strength matter

Cutting screws are used in applications requiring frequent maintenance because of their stronger, machine-cut thread. They are often used in metal fabrication, aluminum and zinc die castings, wood, and plastics.

How Cutting Screws Work

If you’re considering cutting screws for your next project, it’s important to know how they work. The process includes:

1. A pilot hole is drilled to the correct diameter using a drill bit.
2. As the end of the screw is driven into the pre-drilled hole, the cutting edges remove material as the screw advances.
3. Threads are formed in the surrounding substrate, removing some material and forming chips.
4. A tight, load-bearing connection is created.

With cutting screws, chips form as the substrate material is removed. This is different from thread-forming screws, which displace material and push it aside rather than remove it. Since material is removed, the substrate has a lower risk of cracking or deforming.

Cutting Screws vs. Other Self-Tapping Screws

Cutting screws are considered self-tapping screws, but they are different from other types:

Cutting Screws vs. Thread-Forming Screws

Cutting screws and thread-forming screws differ in the way they handle the material. Cutting screws remove material to create threads, which results in chip formation. Conversely, thread-forming screws reshape material without producing chips, creating threaded holes. Since cutting screws remove material, internal stress is reduced, and cracking is prevented, making them better suited for brittle or hard materials.

Cutting Screws vs. Self-Drilling Screws

Cutting screws and self-drilling screws are different because one option (cutting screws) requires a pre-drilled pilot hole, and the other (self-drilling screws) doesn’t. Cutting screws need a pilot hole for accuracy and control, whereas self-drilling screws create their own hole and threads simultaneously.

Common Types of Cutting Screws

There are various types of cutting screws with their own tip geometries and cutting flute designs. They include:

• Type F: This is the most common option. It features a machine screw thread with multiple cutting flutes, making it ideal for heavy-gauge metals, cast iron, and die-castings.
• Type 1 (Type D): This type features a single flute and a blunt, tapered point. It is best for general-purpose use in metal and plastic and is frequently used for field replacements.
• Type 23 (Type T): This type has a large, triangular cutting area for maximum chip clearance. It is designed for plastics and can also be used for harder materials like metals.
• Type 25 (Type BT): This is similar to Type 23, as it has a large, chip-clearing slot. It also has widely spaced, coarse threads that make it suitable for use on plastics, wood, and soft metals.

These cutting screws have features in common. They are often made of stainless steel or zinc-plated steel for durability and may be coated in black phosphate, black oxide, or titanium nitride. Cutting screws come in both metric and imperial thread sizes. Pan head, flat head, or hex washer head options are common. Cutting screws also commonly feature a Phillips drive, Torx drive, or hex drive.

Materials Suitable for Cutting Screws

Thread-cutting screws work best with certain substrates. They include:

• Steel and other metals, such as aluminum, cast iron, and sheet metal
• Cast materials
• Dense plastics, including thermoplastics and reinforced plastics

Cutting screws are also ideal for brittle materials that might split under the pressure of a thread-forming screw. They are best suited for ensuring strong, precise threads without deforming or cracking the material.

Typical Applications

Cutting screws are used in a wide range of industrial and commercial uses, including:

• Equipment assembly
• Metal fabrication
• Electrical enclosures
• Automotive components

• Machinery maintenance

Cutting screws provide the reliability needed for applications that require repeatable installation and removal. They are also suitable for use where high vibration resistance is required.

How to Choose the Right Cutting Screw

Choosing the right cutting screw is essential to ensure the structure and durability of your project. To pick the right option, you need to consider:

• The material being fastened, such as steel or plastic
• The required screw size and thread pitch
• Corrosion resistance needs (stainless vs. coated steel)
• Head style and drive type
• Load requirements

Ensuring you have the correct pilot hole size is also crucial for optimal performance, as it promotes proper placement, prevents cracking, and reduces drive resistance.

Best Practices for Installation

When installing a cutting screw, which is typically done with a drill or drill driver with an adjustable clutch, it’s best to follow a few guidelines for optimal results. They include:

• Drill the pilot hole to the manufacturer's specifications.
• Use steady torque to avoid stripping threads.
• Clear chips during installation if needed.
• Avoid overtightening to prevent threads from stripping.

Cutting screws can often be removed and reused in non-critical applications if the threads remain intact. Although cutting screws can be installed with hand tools like manual screwdrivers or T-handles,power tools offer better efficiency.

Fasteners Etc., Inc. Supplies High-Quality Thread-Cutting Fasteners

When you’re working on a project, whether it’s DIY or for a contractor, you want the outcome to be durable and perform well. Selecting the correct fastener type helps ensure the best results. Fasteners Etc., Inc. is a knowledgeable supplier for industrial fastening solutions, including cutting screws, self-tapping screws, and thread-forming screws.

We can help you determine the best option for your needs or simply find the right type. For more information or to see how our fastener solutions can streamline your operations, contact us or request a quote today.