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The fundamental rules (and devices) to keep you away from the dangers of your saw.
I once heard that 90% (or more) of all table saw accidents involve some kind of kickback, where the work goes back to the operator. Imagine what would happen to the accident statistics if we could eliminate the backlash altogether. The table saw would go from being one of the most dangerous machines to one of the safest.
I often ask in a show of hands during my safety demonstrations how many people have ever experienced a backlash. Most all shyly raise their hand. So I ask how many people have experienced backlash more than once, and it’s almost the same answer.
It is clear that accidents happen to both the novice and the experienced carpenter, but because something as potentially dangerous as a piece of football being pushed back at more than 100mph would be an experience anyone would ever want to have more than once. ?
Kickback can be a product of through and through cuts. Once it starts you can’t stop it and only Superman can react faster. The kickback zone can actually be anywhere in the store. That’s right, everywhere! The main (and most dangerous) line is towards the operator and directly in front of the blade. However, a “kicked” object can bounce off something and head in any direction, and even boards with a significant width that can be pushed back can rotate sideways.
I believe most carpenters don’t understand the cause and cure for backlash, so let’s take a look at both.
The mechanics of the backlash
Kickback occurs when a piece of wood is unexpectedly thrown back towards the operator. The kickback lift and throw force starts from the back of the blade, not the front.
To better understand how this force is created, unplug the saw and mark any teeth with a marker. Now rotate that tooth to the point where it begins to rise above the table on the back plate of your saw.
If you follow this tooth as it rotates, it will give you a better idea of how a piece of wood is lifted and thrown forward. As the blade rises across the table at the back of the saw, it has an initial vertical lift. As the blade continues to rotate and reaches the top of its arc, the vertical lift begins to transform into a horizontal thrust. As the blade moves from the top of the bow down towards the saw table, the horizontal thrust returns to the vertical one. By now all the force is moving towards the table to start all over again.
To help students understand how much lift a rotary blade has, I move them to the 20 “disc sander (unplugged, of course). As the sandpaper disc rotates, you can safely sand the wood on the side that rotates downward. the table. But move the wood to the lifting side and the workpiece is immediately lifted. A table saw blade works in a similar way.
The causes of the backlash
OK, so we know that kickback occurs in the back of the blade, but what are the series of events that can cause the butt to come into contact with the back of the blade?
By far the most common cause is binding or pinching. This happens when a piece of wood gets trapped between the rotating blade and a stationary object, such as a fence or guard. Below is a list of reasons why actions can roll back:
1. Cut a piece of wood with the miter gauge on the left side of the blade while the guide is used as a stop on the right side of the blade – blam-o!
2. In some cases, kickback occurs if the saw cut closes around the blade.
3. Make sure the guide is parallel to the blade. If the fence is moved inward towards the blade, the wood can come into contact with the rear edge of the blade.
4. Twisted, warped, knotty, crooked, or springy cutting of wood.
5. Freehand cutting or cutting of wood that is not flat on the table, such as a round butt.
6. Losing control of the work or letting go of the wood while in contact with the saw blade.
7. Do not follow while tearing or stop before the cut is complete.
8. Drop the wood, intentionally or unintentionally, onto the top or side of the back of the blade.
9. Back off from a cut.
10. Incorrect setting of machine guards, devices or fasteners.
11. Apply the full pushing force towards the falling or free part of the work instead of pushing towards the fence.
The cures for the backlash
Use the guard. The best cure for kickback is to deny the wood access to the back of the blade. A splitter, especially a dividing knife, is by far the best protection you can give yourself.
Double check all your settings and plan your cuts carefully. Be aware of any pinch points or bindings that might be created during any cut and plan your work first. And while this isn’t a cure for kickback, there are blades that have anti-kickback fingers behind the teeth that limit the chip or depth of cut. These blades are sometimes sold as anti-kickback blades, but they do not eliminate kickback.
Now let’s take a look at two important devices that can help you avoid injury, but only if you use them correctly.
Featherboards and Push Sticks
Dr. Jeffery Greenburg, a brilliant hand surgeon and a rather blond carpenter, told me that he has never treated a patient whose injury occurred due to a pusher or any other safety device. In fact, a common reason for accidents to occur is not using a safety device. Push sticks and Featherboards are easy to make, inexpensive, can be made to any size, and are expendable.
There are many articles, drawings and written details on how to make elaborate rod feeders and feather boards, but most professionals make the simpler types for two reasons: they are quick and easy to make, and when they are cut and nicked you don’t. . i feel so bad. They are the ultimate sacrificial tool.
Featherboards is not a cure-all
Feathers, trampolines, combs, anti-kickback fingers, retractors and magnetic holders hold work down or against an edge and act like a spring. A Featherboard is a solid stock piece with multiple cuts that are evenly spaced along the grain. The end of the workpiece is cut at an angle of 30 ° to 45 °. Featherboards can help minimize kickback, but they don’t eliminate it, as some commercial Featherboard manufacturers suggest.
Featherboards are designed, for the most part, to be attached to the table or fence. Attaching them to the fence is usually not a problem. But fixing it to the table can be a challenge. To get around this, some commercial feather boards have built-in expansion bars that fit into the slot of the gun or heavy-duty magnets. If you use store clamps to secure your duvets, use two clamps to prevent the device from rotating.
If a simple locking solution isn’t readily available, try placing a high strength woven fiber carpet tape on the underside of the duvet. This will keep it on the table but won’t give quite the “hold still” holding power that you can get with a clamp.
Feather boards attached to the fence help keep the wood flat against the table and provide some kick resistance. They can be placed anywhere along the fence where a downward force is needed. Keep in mind that pens mounted on a fence can sometimes be restrictive. Table mounted Featherboards provide strength towards the fence and offer some resistance to kicks. It is imperative that a table-mounted featherboard is never placed beyond the front edge of the blade. When mounted behind the blade, the force will push the wood into the back of the blade.
Correct use of push sticks
The sticks are used to help push the stock through the cut while keeping the fingers away from the blade. A good push stick can help hold work against the table while pushing forward at the same time.
They are an absolute must when cutting narrow or thin stocks. Sticks come in all shapes and sizes, and it’s a good idea to have different types and thicknesses ready to use. In most cases, the width of the push rod should be less than the distance between the saw and the guide.
I prefer to use a push stick that hooks onto the back edge and sits on top of the board. This type of push stick gives me more control and helps prevent the butt from tipping over as it moves past the blade.
It is important to understand when and when not to use a bar feeder. As long as you have your hands on a board when making a cut, you will always have a great degree of control. As soon as you use a push stick, you lose some of that control.
I always recommend that you use your hands to push your work when you are more than 3 “away from the guard – you simply have more control. If your hands will be within 3 inches of the guard, however, a push stick is absolutely necessary.
Keep in mind that you will lose some control. In fact, if you use a bar feeder with a downward force on a board that is off the table, it could cause the board to tip upward. Sticks are not effective or necessary at the start of a cut on a long board.
I keep my push stick close at hand and when my pushing hand reaches that 3 “limit, with my left hand holding the board still, I use my right hand to take the push stick and finish the cut. a second stick to the left of the table so that my left hand also has access to a stick. Keep in mind that sometimes sticks can slip off the butt and cause a very dangerous situation. Always keep the stick securely hooked to the edge or side of the table.
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