SawStop Professional 3HP Table Saw: Difference between revisions
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== Description == | == Description == | ||
StopSaw is a high quality table saw, with the added ability to stop before a serious injury occurs. | |||
As stated in Wikipedia, the saw stops in less than five milliseconds, and angular momentum retracts the blade into the table. The operator suffers a minor instead of serious injury. 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. | |||
=== Specifications === | === Specifications === | ||
Revision as of 00:07, 4 February 2023
Safety
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.
The photos from a YouTube video show an actual injury to 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 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 what Rex felt when the blade struck his thumb. Rex made the video to help others avoid his mistake.
Table saws are 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.
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.
- 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.
The saw manufacturer includes the following warning in the instruction manual for the saw:
Training requirements
Use of this tool requires successful completion of the EQ class "Woodshop I - table saw, jointer, planer, miter saw".
Description
StopSaw is a high quality table saw, with the added ability to stop before a serious injury occurs.
As stated in Wikipedia, the saw stops in less than five milliseconds, and angular momentum retracts the blade into the table. The operator suffers a minor instead of serious injury. 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.
Specifications
- Electrical spec:
- 230 Volts, 60 Hz
- 13 Amps
- 1 Phase
MN Asset Details
TBW
Documentation
TBW
Materials, Tooling, Accessories
TBW
Settings
TBW
Tips and tricks
Laser-cut plywood
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.
Crosscut sled
Making a new sled is pretty straightforward. Just grab some 3/8" stock (see note), cut two runners to a smidge proud of 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!), run it across the table to cut the kerf, and Bob's your uncle. 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 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 PVC (or UHMW PE! 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
Replacing cartridge
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.
External links
- 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 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.
