Solution Summary: Alternative Saw Blades
Using an alternative saw blade designed to reduce noise can help lower the risk of hearing loss.
Description:
Circular saws are commonly used in the construction industry and have a wide variety of applications. Although they can make work quicker and easier, there are several hazards associated with their use. One of these is exposure to hazardous levels of noise. Several manufacturers now offer alternative saw blades that are designed to minimize noise exposure for the operator and other people in their vicinity. Most of these blades have a vibration dampening component on or inside the body of the blade.
Even if a saw blade is not explicitly marked as quiet, there are several things you can look for that will help reduce your exposure to noise while cutting. Blades with a very thin kerf, i.e. cutting thickness (Figure 1) and blades with a higher number of teeth will generally be less noisy.
Figure 1. Side view of a circular saw blade
However, it’s important to keep in mind that blades with a high tooth count may generate higher levels of dust or silica. If possible, operate your saw at the lowest rpm that is practical for the work you are performing. Keep the blade as sharp as possible and maintain the saw regularly. Blades with diamond or carbide teeth produce less noise, stay sharper longer, and can reduce maintenance costs. If possible, clamp your workpiece.
The following saw blades were designed to operate more quietly than traditional blades:
MK Diamond MK-925DSLX Supreme Grade Silent Core Blade
• Price: $407.00 (verified 12/30/18)
• Diameter: 14”, 20”, and 24”
• Materials: brick, block, and other masonry
Courtesy of www.mkdiamond.com
IQ Ultimate Silent Core Masonry Blade
• Price: $270.00 (verified 12/30/18)
• Diameter: 14”
• Materials: general masonry
Courtesy of www.iqpowertools.com
Tenryu Silencer Series
• Price: $60.00 (verified 1/22/19)
• Diameter: 6.5" - 12”
• Materials: wood (crosscutting, finish cutting, general purpose)
Courtesy of www.tenryu.com
Risks Addressed:
Repeated overexposure to noise causes permanent hearing loss and ringing in the ears (tinnitus). It has also been associated with hypertension and other cardiovascular diseases (Girard et al, 2015).
The Occupational Safety and Health Administration (OSHA) requires that workers’ 8-hour exposure (also known as LAeq) remain under 90 decibels, while NIOSH has recommended that it remain under 85 decibels. NIOSH’s recommendations are more protective and preferred for maximum hearing conservation. Table 1 shows how long a worker can safely be exposed to different levels of noise (measured in A-weighted decibels, or dBA) according to both OSHA and NIOSH criteria.
|
dBA |
OSHA |
NIOSH |
|
80 |
32 hours |
>24 hours |
|
85 |
16 hours |
8 hours |
|
90 |
8 hours |
2.5 hours |
|
95 |
4 hours |
47.6 minutes |
|
100 |
2 hours |
15 minutes |
|
105 |
1 hour |
4.7 minutes |
|
110 |
30 minutes |
1.5 minutes |
|
115 |
15 minutes |
28 seconds |
|
120 |
7.5 minutes |
9 seconds |
|
125 |
3.8 minutes |
3 seconds |
Table 1
Many circular saws, miter saws, and table saws can produce noise as high as 95-115 dBA. Using NIOSH criteria, a worker could only operate a 115-dBA saw for 28 seconds before their hearing began to sustain permanent damage.
How Risks are Reduced:
Saw blades that are designed to reduce the risk of hearing loss rely primarily on three mechanisms to dampen the vibrations that cause noise:
1. Laser-cut slots
Some saw blades have several curved or S-shaped slots cut into the body of the blade. These slots are sometimes pre-filled with a softer material such as brass, copper, or resin. The placement and design of these slots absorbs and dissipates vibrations moving throughout the blade.
2. “Sandwich” core
Courtesy of http://publikationen.dguv.de/dguv/pdf/10002/12352.pdf
Saw blades with a sandwich core, or a vibration dampening core, typically have a thin layer of flexible material (sometimes referred to as "viscoelastic" material) sandwiched between the plates that make up the body of the blade. This material absorbs and dissipates energy and vibrations, increasing saw blade stability.
3. Carbide teeth
Courtesy of www.infinitytools.com
The teeth of a saw blade are the only part that makes contact with the workpiece. The sharper the teeth, the cleaner and quieter the cut. Carbide (tungsten carbide or titanium carbide) is harder than steel and stays sharper longer. Most types of carbide teeth can be re-sharpened. Some masonry saws also have diamond grit embedded in the teeth for cutting/grinding especially hard materials.
Regardless of the type of saw blade, there are several steps you can take to reduce vibrations when using any electric saw. Keep your saw in good working order and maintain it regularly. Make sure that the collars (or washers) that hold the blade in place fit snugly. Check your saw for arbor runout, or uneven rotation of the arbor that rotates the blade. Always keep the blade as sharp as possible.
Effects on Productivity:
Quieter saw blades work by dampening the vibrations caused by saw operation. Reducing this vibration results in a cleaner, more uniform cut and reduces the likelihood of rework.
Additional Considerations:
Gas-powered saws are usually louder than electrical saws. If using a gas-powered saw, consider switching to a different type of saw in addition to using a quieter blade.
Regardless of the type of blade or equipment, employers must provide hearing protection devices to workers who may be overexposed to noise. Although all hearing protectors are assigned a Noise Reduction Rating (NRR), most workers do not receive the labeled amount of noise reduction (Murphy et al, 2013). The best way to determine hearing protector effectiveness is to perform fit testing, which uses a computer program and special headphones to gauge the actual noise attenuation of hearing protectors worn by workers.
Contributors:
Sara Brooks, MPH, CPH - CPWR The Center for Construction Research and Training
Bruce Lippy, Ph.D. - CPWR The Center for Construction Research and Training
Edward Zechmann, MS/PE/INCE Bd. Cert. - NIOSH
Availability
MK Diamond Products, Inc.
To obtain information, visit MK-925DSLX Supreme Grade Silent Core Blade
or contact 1-800-421-5830 customerservice@mkdiamond.com
IQ Power Tools
To obtain information, visit Ultimate Silent Core Masonry Blade
or contact 1-888-274-7744
Tenryu
To obtain information, visit Silencer Series
or contact 1-800-951-7297 info@tenryu.com
