Solution Summary: Retracting Blade Table Saw
A Retracting Blade Table Saw, like the SawStop, is an engineering control that can help to reduce table saw accidents. It detects electrical current of the object being cut. When skin, which is more conductive than wood, contacts the blade, a spring aluminum brake stops the blade in less than 5 milliseconds (1/200th of a second). Additionally, the blade is retracted below the table and the power to the motor is turned off.
A Rectracing Sawblade Table Saw monitors electrical current between the blade and the object being cut. Objects with low conductivity, like wood, do not activate the brake. When objects that are more conductive, like skin, contact the blade, the brake is activated and a spring forces a block of aluminum into the spinning blade. When the brake activates, the angular momentum of the blade retracts it below the table and the power to the motor is cut off. After the brake is activated, the blade and the brake must be replaced.
There are four types of Retracting Sawblade Table Saws: contractor saw, professional cabinet saw, industrial cabinet saw, and jobsite saw (portable version).
All Retracting Sawblade Table Saws use 10 inch diameter blades and offer various fence and rail dimensions. The contractor saws features a 1.75 HP motor. The professional cabinet saws are available with 3 HP and 1.75 HP motors while the industrial cabinet saws have 3, 5, or 7.5 HP motors.
Figure 1. SawStop (Photo courtesy of SawStop)
Table saws can cause finger and hand lacerations, fractures, and amputations. There were 79,500 hospital emergency room-treated injuries related to table/bench saws in the United States from 2007–2008. In 95% of the cases, the saw blade was running. The most frequent form of injury from contact with a table saw is lacerations (65%), followed by fractures (12%), and amputations (11%) (Chowdhury, 2008). A Retracting Sawblade Table Saw can reduce table saw injuries because the blade stops when skin contacts the blade, preventing serious injury.
How Risks are Reduced:
The blade from a retracting blade table saw system carries a small electrical signal. The system uses the blade as an antenna as an electromagnetic proximity detector to detect the approach of a user's conductive hand prior to actual contact with the blade. Upon detection of a user's hand, the system disengages a brake into the blade using solenoid to stop it before significant injury can occur.
The SawStop (brand name for the Retracting Sawblade Table Saw) website reports that, “In most cases, such an accident [contact with a table saw in motion] would result in just a nick on a SawStop saw, instead of the devastating injury which would likely occur on an ordinary table saw.” SawStop also claims that their table saws "reduce the risk of serious accidents and improve classroom safety, allowing you to focus on teaching your students…”
Safety and health experts believe Retracting Sawblade Table Saws can reduce the risk of finger and hand injuries. While there have been no independent published studies on the Retracting Sawblade Table Saw’s effectiveness of reducing finger and hand injury, the Consumer Product Safety Commission (CPSC) published the results of a voluntary customer survey. In over 1100 entries since 2005, the deepest allowable cut was 3 mm (CPSC, 2011).
Effects on Productivity:
SawStop has no effect on worksite productivity
The average indirect cost for a workplace amputation is $45,608 (Sikes) and engineering solutions such as the Retracting Sawblade Table Saw may be effective in reducing amputations. The Table Saw Safety Act is a bill in California that would require Retracting Sawblade Table Saw technology on all table saws after January 1, 2015.
Using table saws creates wood dust exposure that can cause a variety of adverse health effects such as eye and skin irritation, allergies, reduced lung function, asthma, and nasal cancer. The professional cabinet saw and industrial cabinet saw models of the Retracting Sawblade Table Saw have dust collection systems.
Dan Anton, PT, PhD, ATC; and Kevin Wright, SPT – Eastern Washington University