Cutting with any type of circular saw creates a large amount of noise. This has negative effects on the equipment and woodworker. At times, this noise level can reach as much as 120 dB! This level of noise can have a negative impact on the workers doing the cutting and everyone around them; lowering efficiency, causing headaches and even causing hearing loss during longer exposure. For this reason, special noise-reduction saw blades were developed. Despite this fact, it is extremely important to use hearing protection whenever cutting with any type of circular saw.
Energy Waste and Cause
The noise that a saw blade makes is pure wasted energy. Energy that could be better expended in cutting the material which the saw is supposed to be cutting is now lost. The higher the noise level, the more wasted energy. Saw blade noise comes from two place; vibration and friction. The vibration in a saw blade is a combination of motor vibration being transmitted to the blade, inconsistencies in the material being cut, and inconsistencies in the manufacture of the blade. Two out of three of these problems can be dealt with, while the inconsistencies in the wood have to be lived with.
Spinning will always have air turbulence as a consequence, making the aerodynamics of blade an important segment. When idling, saw blade produce way less noise than when cutting. Expansion slots, plate thickness and tooth shape determine how the circular blade slices through air. However, it’s a small factor comparing to the noises caused by vibrations.
Maintaining the Saw Motor
Motor vibration is caused more than anything by an out of balance motor and poor quality bearings. While motors are designed to be symmetrically balanced, they aren’t perfect. A high quality motor will often have a balanced rotor, much as tires on a car are balanced. Ball bearings are generally better than simple bearing sleeves, although many motors only have bearing sleeves. Maintaining the bearings lubricated is an important part of maintaining any motor, reducing wear on the bearings, thereby reducing the possibility of vibration.
Lowering the Noise
The most significant impact on noise levels have: circular saw speed, teeth number and sawtooth profile, gullet width and depth, saw blade thickness, diameter and purpose. Quality circular saw blades are designed with a number of features to reduce vibration. To prevent stress and noise caused by vibrations, vibration dampener slots or holes and noise reduction shoulders are added, whilst some parts of blade plate are made of sound-absorbing materials. Copper plugs reduce operational vibrations and radiated noise. Precision manufacturing with a perfectly flat plate and well ground teeth is important too. Carbide tipped saw blades will generally create less vibration, lowering the noise. Another thing which can be done to lower noise is to add noise reduction collars and vibration dampeners. While these can lower the saw’s capacity for depth of cut, they reduce vibration and associated noise.
Lowering RPM of circular saw to a half can reduce the noise by about 10dB(A). The same reductions could be achieved by re-sharpening a dull circular saw blade. Resonant frequency of the circular saw blade is the critical speed at which the saw blade starts to tremble. It results in shrill sound; the saw blade is the most vulnerable now.
Friction is a given with saw blades. However, friction can be reduced by the design of the teeth, using carbide tipped saw blades (because the teeth are wider than the plate) and coating both the plate and the teeth. Having Tungsten Carbide Tipped (TCT) tooth pattern can greatly reduce the undesired response. While the necessary friction of cutting will still be there, these steps will eliminate all unnecessary friction, lowering the radiated noise from the saw blade.
The number of teeth a saw blade has also affects the noise level. Saws with more teeth and correspondingly smaller gullets will produce less noise than saw blades with a lower number of teeth. Each tooth is taking a smaller “bite” and creating less vibration than a larger tooth will. The grind of the tooth will greatly affect the friction, as well as well-adjusted clearance angles, thereby affecting the amount of noise produced.
Finally, how one cuts with the saw will affect the noise. Trying to take too big a bite at one pass or trying to push the saw blade through the material too fast will increase noise levels, while reducing blade life at the same time. A smooth, even cut, which isn’t going through too much material at once, will produce considerably less noise. At times, this might mean taking multiple passes to cut the material, especially with thicker materials.