The hum of a circular saw is most often associated with cutting wood, but for many fabricators, fitters, and engineers, this versatile power tool is an essential part of working with metals. However, attempting to cut aluminium extrusion or a brass plate with a standard wood blade is a recipe for disaster. The blade will skip, the metal will deform, and the cut will be dangerously unpredictable.
Cutting non-ferrous metals—like aluminium, brass, and copper—is a specialised task that requires a specific setup. It is not about brute force; it is about precision, control, and most importantly, using the right Circular Saw Blade. With the correct blade and technique, your circular saw can produce clean, accurate, and burr-free cuts in metal, saving you time and effort. This guide will walk you through the essential steps to get it right.
Ferrous vs. Non-Ferrous: A Critical Distinction
Before we discuss blades, it is vital to understand the difference between metal types. Your circular saw is not designed for cutting ferrous metals like steel, iron, or stainless steel. These materials are incredibly hard and dense, and attempting to cut them with a standard circular saw can cause catastrophic blade failure and serious injury. Ferrous metals require specialised, low-RPM "cold cut" saws.
This guide focuses exclusively on non-ferrous metals, which are softer and have different properties:
- Aluminium: Lightweight, soft, and an excellent conductor of heat.
- Brass: An alloy of copper and zinc, it is harder than aluminium but still relatively easy to machine.
- Copper: Very soft and ductile, but can be "gummy" and prone to clogging the blade.
These metals can be cut safely with a circular saw, provided you use a blade engineered for the job.
Ideal Blade Features for Cutting Non-Ferrous Metals
A wood blade rips and tears fibres. A metal-cutting blade needs to shear away material with precision. To do this, it requires a completely different design.
Tooth Geometry: Triple Chip Grind (TCG) is Non-Negotiable
The single most important feature of a metal-cutting blade is a Triple Chip Grind (TCG). This geometry uses an alternating pattern of a high "trapper" tooth and a lower, flat "raker" tooth. The trapper tooth makes a rough initial cut, while the raker tooth follows behind to clean up the corners.
- Why it's essential: This chipping action is far more durable than the slicing action of a wood blade (ATB). It prevents the teeth from catching or digging into the metal, reducing the risk of kickback and ensuring the blade can withstand the repeated impacts of cutting a hard material.
Tooth Count: High is Better
For a smooth, clean finish on metal, you need a high tooth count. A typical 165mm non-ferrous blade might have 50-60 teeth, while a 254mm blade could have 80 or more. The more teeth engaged in the cut at any one time, the less work each individual tooth has to do. This distributes the load, reduces vibration, and leaves a much cleaner edge with fewer burrs.
Hook Angle: Negative is Safest
The hook angle refers to how far forward or backward the teeth lean.
- Positive Hook (for wood): Leans forward to aggressively "pull" the material into the blade. This is great for wood but dangerous with metal, as it can cause the blade to climb or snatch the workpiece.
- Negative Hook (for metal): The teeth lean slightly backwards (e.g., -5°). This creates a less aggressive cutting action, pushing the material away from the blade rather than pulling it in. This gives the operator far more control and is a critical safety feature for cutting hard, slick surfaces like aluminium.
Special Coatings
When cutting aluminium, the heat from friction can cause small chips to melt and weld themselves to the blade's teeth and body (a process called "galling"). An anti-friction coating (like PTFE) helps to prevent this by creating a non-stick surface, ensuring chips are ejected properly and keeping the blade running cool.
Getting the Cut Right: Speed, Feed, and Lubrication
Your technique is just as important as your equipment. Metal does not forgive sloppy work.
Saw Speed (RPM)
Metals should generally be cut at a slower RPM than wood to reduce heat build-up. If your saw has a variable speed dial, turn it down. If not, the negative hook angle on your blade will help to control the cut. Always ensure your saw's RPM is below the maximum RPM rating printed on the blade.
Feed Rate
The golden rule is slow, steady, and consistent.
- Do not force the saw: Let the blade do the work. Pushing too hard will cause the motor to bog down and the blade to overheat.
- Maintain momentum: Once you start the cut, complete it in one smooth pass. Stopping and starting in the middle of a cut can leave marks and increase the risk of the blade binding.
Lubrication is Key
Heat is the enemy when cutting metal. A lubricant or cutting fluid helps to cool the blade, lubricate the cut, and flush away chips.
- For Aluminium: A wax stick or a specialised aluminium cutting lubricant is highly recommended. You can apply the wax directly to the blade (when stationary) or along the cut line.
- For Brass and Copper: A light machine oil can work well.
- The Benefit: Lubrication will dramatically improve the quality of the cut and significantly extend the life of your Circular Saw Blade.
Safety First: Essential Equipment
Cutting metal produces sharp, hot chips that fly at high velocity. Your standard woodworking safety gear needs an upgrade.
- Full-Face Shield: Standard safety glasses are not enough. A full-face visor is essential to protect your entire face from flying metal chips. Wear safety glasses underneath the visor for double protection.
- Hearing Protection: Cutting metal is loud. Always wear ear defenders.
- Gloves are a Must: Unlike with woodworking, sturdy leather gloves are recommended when cutting metal. They will not protect you from a spinning blade, but they will protect your hands from the razor-sharp, hot chips and the sharp edges of the freshly cut workpiece.
- Secure Your Workpiece: This is non-negotiable. Metal is slick, and a vibrating saw can easily cause it to shift. Use robust clamps to lock the material down to a stable workbench. Never attempt to cut a piece of metal that is not securely clamped.
Recommended Non-Ferrous Cutting Blades
At Key Blades & Fixings, we stock blades specifically engineered for the challenges of cutting non-ferrous metals. When browsing our Circular Saw Blades, look for blades with the following characteristics:
- Product Name: Will often include "Aluminium," "Multi-Material," or "Non-Ferrous."
- Tooth Geometry: Must be listed as TCG (Triple Chip Grind).
- Hook Angle: Should specify a Negative Hook Angle (e.g., -5°).
- Tooth Count: Should be high for the given diameter (e.g., 50+ teeth for a 165mm blade).
A prime example from our range would be a 190mm 60T TCG Negative Hook Blade. This blade combines all the essential features for safely delivering a crisp, clean cut in aluminium extrusions, brass sheets, and other non-ferrous profiles. Investing in the right blade turns a difficult task into a simple, precise operation and ensures your tools and, more importantly, you, stay safe.