Imagine this, you want to cut a piece of metal, but the only cutting tool in your store is a circular saw. Since a circular saw is mainly used to make straight cuts on pieces of lumber, you’re left wondering whether using it to cut metal will cause damage. A damaged circular saw can be costly to repair, especially when the arbor is affected.
A circular saw can cut metal when fitted with the right blade for the job. Most circular saws have 7-1/4 inch (184.15 mm) framing blades suitable for wood but can’t cut through metals correctly. Therefore, you need a 5-3/8-inch (136.53 mm) blade size to cut metal with a circular saw.
In the rest of this article, I’ll discuss the factors to consider when cutting metal with a circular saw. I’ll also share tips for successfully cutting metal with a circular saw. Let’s get started!
Cutting Metal With a Circular Saw: Factors To Consider
Cutting metal with a circular saw requires utmost care for your safety and your tools. Since these saws are safer for wood than metal, they need some modifications before using them for metal-cutting purposes.
Some factors to consider when cutting metal with a circular saw include:
The Type of Blade
There are two main types of circular saw blades:
- Steel blades
- Carbide blades
It’s worth noting that metal is among the hardest materials to cut. Therefore, the blade must be durable and extremely sharp.
Steel blades are suitable for cutting wood and thin metal sheets since they can’t withstand the cutting pressure from materials with high tear and wear.
Carbide blades are characterized by high strength and hardiness, making them the best option for cutting metals. These blades are made from cobalt and tungsten carbide, highly-durable materials. These materials make it possible for the blades to withstand heavy metals with high degrees of wear and tear during the cutting process.
Ferrous and non-ferrous metal cutting should also guide your choice of blade. High-speed steel (HSS) metal saw blades can work well for non-ferrous metals like aluminum, brass, and copper.
Ferrous metals are those with iron, such as steel, galvanized steel, and cast iron. These require a blade made of harder material like carbide for successful cutting.
The Number of Teeth on the Blade
Metal cutting blades have varying teeth for a reason; they determine the metal thickness the blade can cut.
Blades with fewer teeth are suitable for cutting thicker metals. Fewer teeth produce bigger chunks, meaning the blades cut through the metal faster with rougher edges.
An easier way to know the best saw teeth for a specific metal is by determining whether the metal is ferrous or non-ferrous. Ferrous metals are thicker and require blades with fewer teeth, between 30 and 70.
On the other hand, non-ferrous metals are thinner and require blades with more teeth, ranging from 60 to 100.
A rule of thumb is to reduce the tooth per inch of the metal saw blade with an increase in the metal thickness.
The Size of the Blade
The good thing about circular saws is that they are versatile. You can use blades of different sizes for cutting. However, you must know that blade size affects the saw’s cutting power.
While smaller blades are suitable for thinner metals, their larger counterparts are effective in cutting thicker ones.
For instance, a 4.5-inch (114.3 mm) blade is best for thin metal materials like aluminum sheets and conduit pipes. Meanwhile, 5 ⅜-inch (136.53 mm) blades can effectively cut thick metals such as steel plates and angle iron bars.
The speed at which the blade rotates affects the quality of your cut. For metal cutting, it’s best to use a slow-speed setting on the saw to prevent overheating or damaging the blade.
At no load, 5,000 revolutions per minute (rpm) is the average speed at which a circular saw can cut metal. However, this speed can cause the blade to overheat, and if not durable, it can break due to the high frictional force.
The best way to prevent such an occurrence is by gradually reducing the cutting speed as you cut through the metal. It also narrows down to whether the metal is ferrous or non-ferrous.
Speeds between 3,000 to 6,000 rpm are suitable for non-ferrous metals. Otherwise, use speeds ranging between 1,800 to 3,500 rpm for ferrous metals.
Besides preventing the blade from overheating, using the right speed makes the circular saw stable. It also ensures smooth cuts and minimal friction. Therefore, a shaking circular saw indicates that you’re using the wrong speed for the material.
Your Saw’s Depth Setting
Circular saws have a depth setting knob or lever to adjust the depth at which the blade can cut into materials. It’s best to set the saw at a shallow depth when cutting metal. This will ensure the blade doesn’t overheat and break during the cutting process.
It’s also essential to set the depth of your saw according to the thickness of the metal material. Otherwise, you risk having a jagged or incomplete cut.
For thinner metals like aluminum sheets, set the depth at 1/8 inch (3.18mm). Meanwhile, a 1/4 inch (6.35 mm) cutting depth will work well for thicker metals like steel plates.
A rule of thumb for selecting an appropriate cutting depth is to ensure the blade doesn’t exceed 1/4 inch (6.35 mm) of the workpiece’s thickness.
Metal cutting generates a lot of heat at the cutting zone. The heat is generated in the following ways:
- Metal deformation in the shear zone along the cutting line.
- Blade friction as it rubs across the metal.
- During the separation process as the metal is pulled apart.
The heat can cause harm to the blade and the material being cut. Thus, applying lubricants and cooling agents is necessary to reduce the heat generated due to the cutting process.
Apart from reducing heat generation, lubrication makes your cutting easier in the following ways:
- It eliminates the possibility of the blade grabbing the workpiece.
- Eliminates friction between the saw blade and the workpiece. Consequently, this reduces the energy needed to push the saw through the workpiece.
- Prevent metal chips from sticking to the saw blade, causing excessive wear on the blade.
- Washing debris off the workpiece surface.
You can use lubricating sprays or wax sticks at the cutting zone to reduce heat and friction during metal cutting with a circular saw. Just be sure not to overdo as it can cause kickbacks.
A slight mistake when installing the blade can cost a fortune. Blades in circular saws usually rest upon an arbor, a cylindrical shaft that holds the blade in place.
When installing the saw blade, ensure it’s adequately secured onto the arbor before turning on the power. Otherwise, you risk having an unstable and vibrating saw and potential injury.
Since this is a crucial safety step, here is the procedure to safely install blades on a circular saw:
- Unplug the circular saw from the power source.
- Move the guard aside to access the blade you want to remove.
- Use a spanner to remove the bolt holding the blade onto the arbor. It’s recommended to hold the blade in place while loosening the bolt to prevent injuries.
- Once the bolt is loosened, remove it using your hands and pull out the blade.
- Before installing the new blade, check its rotation direction.
- Install the blade over the shaft, ensuring that the side with printings faces outside.
- Insert the plunge first, followed by the bolt.
- Use a spanner and a wrench to tighten the bolt.
Here is a video demonstrating the above procedure:
Workspace positioning is critical when cutting metal with a circular saw. In this case, workspace positioning entails how you position yourself and the workpiece.
You must ensure that the workpiece is securely clamped onto a stable surface to prevent slipping during the cutting process.
Moreover, it’s advisable to position yourself in such a way that your hand is never near the saw blade. You can achieve this by keeping your body away from the line of cut and using both hands to push the saw smoothly through the workpiece.
Tips for Cutting Metal With a Circular Saw
- Align and tighten all fittings and attachments: This includes ensuring proper blade installation and checking for any loose screws or parts on the saw.
- Make sure you have enough space to cut: Moving a circular saw can be tricky, especially when cutting metal. Therefore, you must have ample workspace and room to maneuver the saw without obstructions.
- Check the cutting depth: Confirm that the cutting edge is within ¼ inch (6 mm) of the workpiece’s thickness.
- Mark the cutting line: Use a marker pen or scoring scribe to mark the cutting line before starting the saw. The mark helps to maintain a straight cut and prevents veering off the intended path.
- Align the blade with the cutting line: Connect the circular saw to the power and align the blade with the cutting line you marked.
- Cut slowly and steadily: Turn the saw on and start cutting at a slow, steady pace. You should increase the speed gradually as you cut through the workpiece.
- Cool down your saw blades after use: You should let the saw blade cool down before cleaning or storing it away. This helps prevent damage to the saw blade or other properties.
Safety Tips When Using a Circular Saw
Circular saws are risky tools that must be used with care. The blade is the most dangerous part, accounting for 80% of all circular saw accidents. Therefore, you must take the following precautions to remain safe while using this saw:
- Wear protective gear: You must wear goggles, gloves, and appropriate footwear to protect your eyes, hands, and feet from potential injuries.
- Stay vigilant: Keep your focus on the saw and workpiece while cutting. You should avoid distractions such as talking or using a cell phone.
- Stay alert: Stay aware of your surroundings to prevent tripping or bumping into obstacles.
- Inspect the workpiece: Inspecting the workpiece before cutting enables you to identify nails and other foreign objects that may damage the saw blade.
- Create a stable workspace: The workspace must be clear and not cluttered to prevent tripping or losing your balance while operating the saw.
- Always wait for the blade to cool before touching it: Saw blades are usually hot after cutting metals. Therefore, you may burn your skin if you touch them immediately.
- Watch out for metal chips: Metal chips may fly off during the cutting process and cause injury since they are hot and sharp. Using a circular saw with a chip collector is the best way to protect yourself from these chips.
- Keep the blade clean: Keeping the blade clean prevents clogging and improves its efficiency in cutting metal. Therefore, you should clean or replace dull blades regularly for optimal performance.
A circular saw can cut metal effectively with the right blade and cutting techniques. It’s an incredibly versatile tool that proves its worth in any woodworking or metalworking project.
You must be cautious when operating a circular saw and prioritize safety.