SawStop Professional 3HP Table Saw
Table saws are one of the most dangerous machines in a shop. According to the Consumer Product Safety Commission, 38,000 or more serious accidents occur each year, averaging once every 15 minutes.
Table saws are especially dangerous because the operator holds the material being cut, instead of the saw, making it easy to accidentally move hands into the spinning blade. In contrast, when using portable circular saws, the material remains stationary, as the operator guides the saw into the material.
Accidental blade contact
The photos from a YouTube video show an actual injury to woodwork Rex Krueger's thumb caused by improper use of a StopSaw. He did not loose his thumb, but he did require medical treatment in an emergency room. Rex had an irregular laceration of the tip of the thumb. Two or three teeth of the blade penetrated his thumb nail and flesh to about 2 cm.
Rex attributes his injury to his failure to use a blade guard. A link to the video is in the section External links. The video tells how the accident happened and what Rex felt when the blade struck his thumb. Rex made the video to help others avoid his painful mistake. Rex advised spending $300 for an overarm dust collector, which includes a well designed blade guard. Rex said that his injury would have been much worse, if it were not for the safety features of his SawStop.
The table saw at Maker Nexus is equipped with two important safety devices, a blade guard and a riving knife. One or the other of these safety devices must be used at all times:
- Using the blade guard is one of the most important steps you can take to prevent injury. Many table saw injuries occur when the blade guard is either not being used or not being used properly. The blade guard covers the blade, and lifts up just enough to allow your material to slide into the blade. The blade guard can be used only for cuts that go all the way through the material. For cuts that do not go all the way through your material, use the riving knife on the table saw, or use a router instead of the table saw.
- The riving knife should be used for cuts that do not go all the way through material, such as dado cuts, grooves, and rabbet cuts, or extremely narrow cuts. When you finish using the riving knife, replace it with the blade guard.
- Injuries often occur because the blade guard is removed for a special job, but the blade guard remains off after the job is finished. If you remove a blade guard, put it back when you get done using the saw.
The manufacturer of the SawStop includes the following warning in the saw's user manual:
Not completely safe
The SawStop manufacturer's marketing materials exaggerate the safety of their saw. The marketing materials show fingers with nothing but a slight nick. They do not show more serious injuries, such as what happened in Rex Krueger's video. Instead of striking the blade from the front, his left thumbnail touched the side of the blade, which suddenly pulled the rest of his thumb into alignment with the blade. The safety system saved his thumb, but he still needed stitches in an emergency room. The accident would not have happened if he had been using the blade guard.
Blade guards are designed to protect workers from injury. Properly designed blade guards do not create a new hazards:
1910.212(a)(2) General requirements for machine guards.
Guards shall be affixed to the machine where possible and secured elsewhere if for any reason attachment to the machine is not possible.
The guard shall be such that it does not offer an accident hazard in itself.
After the power is shut off, the StopSaw blade continues to spin for about 8 seconds, remaining hazardous. Be sure to wait for the blade to completely stop, before moving materials or adjusting the saw.
Use of this tool requires successful completion of the BOSS class "Woodshop I - table saw, jointer, planer, miter saw" or an equivalent check-off.
StopSaw is a high quality table saw, with the added ability to stop before it amputates a finger. Because of the high resistance of human skin, the blade will not stop, until it has broken through skin. You may not loose a finger, but you will need medical treatment in an emergency room.
As stated in Wikipedia, the saw stops in less than five milliseconds, and angular momentum retracts the blade into the table. The design takes advantage of the difference in conductance and capacitance between wood and flesh.
An oscillator generates a 12-volt, 200-kilohertz (kHz) pulsed electrical signal, which is applied to a small plate on one side of the blade. The signal is transferred to the blade by capacitive coupling. A plate on the other side of the blade picks up the signal and sends it to a threshold detector. If a human contacts the blade, the signal will fall below the threshold. After signal loss for 25 micro seconds (µs), the detector will fire. A tooth on a 10-inch circular blade rotating at 4000 RPM will stay in contact with the approximate width of a fingertip for 100 µs. The 200-kHz signal will have up to 10 pulses during that time, and should be able to detect contact with just one tooth. When the brake activates, a spring pushes an aluminum block into the blade. The block is normally held away from the blade by a wire, but during braking an electric current instantly melts the wire, similar to a fuse blowing.
- Electrical power requirments:
- 230 Volts, 60 Hz
- 13 Amps
- 1 Phase
MN Asset Details
To be written...
The SawStop owner's manual includes two pages of warnings and two pages of safety information.
Materials, Tooling, Accessories
To be written...
To be written...
Tips and tricks
Do not use the SawStop table saw to cut plywood after it has been cut by a laser, because the laser carbonizes wood, and carbonized wood is conductive.
Making a new sled is pretty straightforward. Use 3/8" stock (see note), cut two runners to a about 3/4" with the table saw blade at an angle, affix to a flat piece, put on a back plate (the one tricky bit; as close to perpendicular as you can get it!), and run it across the table to cut the kerf. The one that we had before used metal runners, which are very nice, but not at all necessary for most jobs.
Note on materials: Plywood or Medium-density fiberboard (MDF) for the base is standard and works great. For the runners, solid wood is oddly enough a poor choice here, because it will expand/contract by its grain. Plywood works alright for runners if you orient their cut such that any expansion tends to pull the sled tighter to the table, but MDF is better. Unfortunately, MDF generally doesn't typically come in 3/8", so needs to be pulled down to the proper size. Best is something like poly vinyl chloride (PVC) (or ultra high molecular weight (UHMW) polyethylene! Super slide-y!) that won't expand/contract in response to temperature or humidity. But please don't build the base out of plastic, especially a low-temperature one like UHMW, as it will potentially melt onto the blade.
Back to MN-S Wood Shop Equipment List
Follow these steps to replace a cartridge:
- Ensure everyone is safe. Check for cuts, scrapes, however minor.
- Unplug saw.
- Identify how it was triggered—check what jigs, if any, were being used. Figure out where in the cut it stopped. Take pictures of setup and position as best you can so we can address any safety issues. Take pictures of material where cut was happening.
- Remove SawStop cartridge and blade (they will be locked together, this can be challenging—youtube if you need help).
- Notify member they will be invoiced for cost of cartridge and sawblade unless we are able to show it was not their fault (sometimes it isn't, but that's about a <1% chance).
- Install new cartridge & blade—check and confirm proper spacing between blade & cartridge with yellow spacer. Err on the open side - too close can accidentally trigger the sawstop feature as well—especially if people don't check when changing blades.
- Fill out a Sawstop trigger report and give it to a manager.
- SawStop article on Wikipedia
- StopSaw company's home page
- Sawstop Injury I didn't think this could happen, Rex Krueger's video describing his actual StopSaw injury
- Survey of Injuries Involving Stationary Saws—Table and Bench Saws, U.S. Consumer Product Safety Commission
- Table Saw Guards—Expert Introduction to Table Saw Safety, skill and experience do not provide adequate protection
- Table saw injuries: epidemiology and a proposal for preventive measures, many injuries to students
- What You Don’t Know About European Saws, cost more, but include more accessories.