Cutting Out Mishaps
JERROLD SCHARNINGHAUSEN, PH.D.
Directorate of Assessments and Prevention
U.S. Army Combat Readiness Center
Fort Rucker, Alabama
Of the many types of power saws available for purchase, the circular saw is one of the most popular. This utilitarian workhorse is among the most common wood-cutting tools used in carpentry and can be a useful addition to a do-it-yourselfer’s toolkit. However, if used incorrectly or recklessly, the saw’s exposed blade is a laceration and amputation hazard.
Circular saws are equipped with upper and lower guards that surround the blade when it is not engaged. The lower guard opens as the saw is pushed into the item being cut, exposing the blade, which spins about 120 mph. More than 40,000 circular saw accidents happen each year, with 40% resulting in a permanent partial disability. This represents approximately 30% of all of saw injuries. Safety requirements for using a circular saw include:
- Put on personal protective equipment (PPE) before handling the saw. This safety tip is essential. PPE should be put on before handling any power tool, not just a circular saw. Hearing protection is necessary, as the noise levels can exceed 85 dBa once a cut is started. Eye protection is needed to protect you from the dust and projectiles produced while cutting. The dust produced can also be harmful when inhaled into your lungs, so a respirator may be required.
- Inspect the saw prior to use. You need to perform a pre-operation check on every part of the circular saw to ensure it’s working properly. Check the retracting lower guard to make sure it retracts and recovers properly. Never use any circular saw with a defective lower guard. Make sure the circular saw is de-energized when performing the inspection.
- Learn to hold the saw properly. Hold the saw with your primary hand on the main handle and your alternate hand holding the auxiliary handle or the circular saw knob. Both hands should not cross each other. To prevent hand contact with the rotating blade, it is essential that operators use the saw’s front and rear handles. With two hands on the saw handles, neither can come in contact with the blade. Another advantage to using both handles is the additional control that two-handed operation provides, thereby reducing the tendency of the saw to move suddenly and dangerously. To achieve the proper two-handed operation with the saw, the item being cut cannot be supported by the operator. Modern saw instruction manuals and correct acceptable practices require that the wood be securely clamped to a stable table or other suitable support. This substantially reduces the danger of laceration or amputation.
- Cut on a stable platform. A circular saw may offer the ultimate in portable convenience, but that doesn't mean it's safe to cut lumber braced against your knee. Use sawhorses. Reduce the chance of the blade binding in the kerf by cutting outside the sawhorse edges, never between the rails of two sawhorses.
- Use a safe depth of cut settings. Prior to cutting with a circular saw, you have to set the depth of the cut to match the thickness of the board. Set the blade depth so that the tips of the teeth just barely protrude beyond the thickness of the board (this applies to table saws as well) to minimize the hazard of accidental blade contact with your sawhorse.
- Only use sharp blades. When cutting with a circular saw, the object is to direct the saw through the cut, not to force the saw through the material. If you discover that it is taking more effort to complete the cut, then the most obvious reason is a dull blade that should be replaced. Sharp blades make the work easier and safer. The blade’s teeth are measured in teeth per inch (TPI). A higher TPI gives a smoother cut that requires less sanding. Blades with a lower TPI produce faster cuts that are good for rough work. Multi-purpose saw blades are available, but specially designed varieties should be used when cutting materials like metal, cement fiber board, ceramic tile or plastic.
- De-energize the saw when not in use. When finished using the saw, the safe thing to do is disconnect it from the power source. If the saw is still energized, it could be switched on accidentally and cause injury. The same principle applies when you’re trying to swap out old or dull blades with new, sharper ones. Disconnect the power source before attempting to swap the blade.
- Never use a defective saw. If you find the circular saw is not working properly, turn it off immediately. This could be as subtle as an unusual vibration or sound. Do not use the saw again until it is properly serviced.
- Do not overreach. When trying to rip long boards with your circular saw, do not overreach or try to cut farther than your hands can extend. Ensure you maintain proper balance and footing with both hands on the saw.
- Keep power cords out of the way. This one is pretty obvious, as cutting a power cord could result in electrocution. Always keep cords out of the cut area to avoid a mishap.
- Check for obstructions in the stock. Before cutting any material, especially wood, make sure there are no embedded obstructions such as nails, screws or staples. Cutting a nail or screw embedded in the wood could cause damage to your circular saw or result in injury.
- Secure the stock or board before cutting. Make sure the material you plan to cut is secured with clamps to avoid any movement during the cut. An unsecured stock is unsafe to cut and should not be attempted.
Here's how to use a circular saw:
- Measure and mark the cut line.
- Clamp the material firmly to a workstation.
- Attach the appropriate blade to the saw.
- Set the blade depth.
- Confirm the bevel angle.
- Plug the saw’s cord into a power source or attach its battery.
- Rest the base of the circular saw, called the shoe, on the edge of the material and near the cut line. For a regular straight cut, the shoe and the blade are at a 90-degree angle. The angle of the shoe can be adjusted so that body and blade of the saw are tilted to make a bevel cut through material.
- With the blade next to — but not touching — the stock, press the lock switch and pull the trigger to get the saw to full speed.
- Keep the shoe firmly on the surface and ease the saw forward to the cutting line with the trigger engaged.
- Guide the saw along the cutting line while keeping the shoe flat on the stock.
- Let the saw do its work. Pushing with too much force can strain the motor.
- Release the trigger to stop the blade when the cut is complete, then lift the saw and place it on the workbench.
The Occupational Safety and Health Administration warns of three major hazards workers face when using a circular saw: the point of operation, kickbacks and flying particles.
- Point of operation. Injuries can occur if an operator’s hands slip while cutting or if they’re too close to the blade during cutting. To help prevent these injuries, make sure hands are out of the line of the cut.
- Kickbacks. Kickbacks occur when blade “catches” the stock and throws it back toward the operator. This is usually due to an incorrect blade height or if the blade has not been maintained properly. Kickbacks are more likely to occur when ripping rather than crosscutting. Help prevent kickbacks by: using clamps to hold down stock; using the correct blade for the cutting action. For example, don’t use a crosscut blade for ripping; operating the saw at the manufacturer’s recommended speed; keeping the saw blade sharp; leaving enough clearance space for stock; and supporting all parts of the stock, including the cut and uncut ends, scrap and finished product.
- Flying hazards. Operating a circular saw can cause wood chips, broken saw teeth and splinters to be thrown from the blade and toward anyone nearby. Help prevent flying particles by immediately removing any damaged saw blades from service.
A circular saw can be a valuable tool on many home improvement projects. By following some basic precautions and wearing the proper PPE, circular saws can be operated safely.
Did You Know?
About 125,000 serious injuries occur in the U.S. each year related to the use of portable and fixed power saws, resulting in losses in the tens of millions of dollars. Hand and finger blade contact is involved in the majority of these accidents.