The value of a riving knife cannot be overstated! If you’ve ever dealt with a circular saw, you’ll understand what I’m talking about. Without it, one of the most terrible phenomena known as backfire can occur.
The riving knife on a table saw is a vital piece of safety equipment for the tool. A riving knife is a flat piece of metal that is mounted just aft of the saw blade.
When you push a workpiece through the saw blade, the riving knife is designed to keep the two cut sections of the board from closing up, thus pinching the saw blade and causing dangerous kickback.
Rip cuts are especially prone to kickbacks, and it is here that the riving knife is most important.
Even though a riving knife is effective in reducing the possibility of a kickback, it cannot prevent it entirely, which is why it is always advisable to follow the basic rules of use for a table saw.
Wear appropriate clothing, use properly approved safety glasses and hearing protection when necessary, keep your hands safely away from the saw blade, and stand in a manner so that if the board does somehow kickback, you’ll be less likely to sustain an injury.
The Mechanics of the Riving Knife
On most table saws, the riving knife mounts to the saw’s trunnion— the sturdy mechanism beneath the saw table that raises and lowers the saw blade.
Typically, the riving knife has a release mechanism that can be accessed by removing the table insert from the top of the saw table. In many cases, this release mechanism allows the riving knife to be adjusted higher or lower in relation to the saw blade, and the knife typically is shaped so that the gap between the blade’s cutting teeth and the edge of the knife is less than 1/4 inch.
This allows for maximum effectiveness when keeping the two halves of a freshly cut board separated as it is pushed through the blade. Normally the riving knife raises and lowers along with the saw blade as its depth is adjusted, allowing the riving knife to “hug” the blade no matter what position it is in.
Unlike a splitter, which must be removed from the saw for crosscutting, a riving knife can remain in place for crosscuts and any type of cut where the saw kerf runs entirely through the thickness of the board. There very few instances in which the riving knife is not appropriate.
When to Remove the Riving Knife
When you watch woodworking shows on TV, you’ll often see that the riving knife, anti-kickback pawls, and blade guards have been removed.
This is done to make viewing the steps involved easier to view on television, but it does a bit of a disservice to the novice woodworker by implying to woodworkers that it’s acceptable to remove these safety devices.
But there are times when you simply must remove the riving knife, or when it is inappropriate to use one. A good example is when using a stacked dado blade to cut a dado or a rabbet. Because this type of blade does not create a through cut, a riving knife would serve no purpose. In fact, it would actually get in the way, blocking the completion of the cut.
Additionally, since most table saws use a 10-inch diameter blade, but most stacked dado blades are 8-inches in diameter, there would be at least a one-inch gap between the edge of the stacked dado blade and the riving knife, which would essentially render the riving knife useless.
In nearly every other case, though, the riving knife should be used when making standard rip cuts and crosscuts with your table saw. It is unobtrusive, and when used in conjunction with other safety features, it makes using your table saw much safer.
How Do Riving Knives Function?
The classic riving knife will mount on the trunnion of your saw. This mechanism goes under the table and pushes the blade up and down. The riving knife has a simple system that allows adjusting it. It normally depends on the saw blade – higher or lower.
As a general rule of thumb, there has to be a gap between the riving knife and the saw blade throughout the entire surface – normally less than 0.25 inches.
Since the distance is low and the knife attaches to the mechanism moving the blade, the knife should practically hug the blade, regardless of the position. From many points of view, the riving knife is similar to a splitter. However, the difference is the splitter has to be removed for crosscutting, while the riving knife can stay there.
A table saw is typically used for cross-cutting and ripping; cross-cutting slices a board across its grain width-wise, ripping cuts lengthwise along the grain. Various conditions experienced while cutting, either way, can cause a partially cut board to move, twist, or have the saw blade’s kerf close up and bind the blade.
Poor blade or fence alignment, operator error, or pre-existing stresses in the wood released by cutting may cause these different and dangerous conditions.
A riving knife rides within the kerf, pivoting on the saw’s arbor in relation to blade height, to maintain an even gap between the two cut sides of the board, preventing jamming which could cause the stock to be forcefully ejected rearward toward the saw’s operator.
Kickback can pull the operator’s hand into contact with the saw blade, as demonstrated by Popular Mechanics.
Forms of kickback
Saw blade “grabbing” occurs more frequently during ripping than cross-cutting (cuts made to wood or stone across its main grain or axis). It can occur with both hand saws and bandsaws but is more dangerous with a circular saw as areas of the circular blade close to the cutting area are moving in different directions. If a bandsaw grabs, the wood is pressed safely down into the machine table (though the saw may jam, stall or break the blade).
If a table saw grabs at the rear of the blade where the teeth are rising up from the table, it may rapidly lift the wood upwards. The wood is then likely to catch the teeth on top of the blade and be thrown forwards at high speed towards the operator. This accident is termed a “kickback”.
Table saw kickback may occur if the saw’s fence is not parallel with the blade, but is slightly closer to the rear of it than the front, causing the fence to push the wood into the rear of the blade.
This is especially likely when cross-cutting sheet materials that are wider than the cut length, which may pivot on the table and jam against the blade.
If a proper cross-cutting jig is not being used, the fence should be adjusted (either slid forward or a false fence added) so the end of the fence stops alongside the blade, leaving a free space for the cut-off to pivot into without binding.
Kickback may also occur when a loose piece of wood, freshly cut free, slips against the back of the blade. Apart from the measures above, this “falling board” may require an assistant to control it.
When Should You Use A Riving Knife?
If you watch woodworking shows, you have probably noticed that most experts remove the riving knife. Blade guards and other forms of protection are also removed. It does not mean that you have to do it too. Instead, they do it for greater visibility for the watchers, but they take a risk.
Generally speaking, the riving knife should be used at all times – with a few exceptions. Standard rip cuts? You need it. Crosscuts? You need it. It will not obstruct you and it can seriously enhance your safety standards.
There are also a few situations when it has to go. If you use a stacked dado blade, you should know that it cannot create a through cut. At this point, the riving knife is useless. It might be in your way a little. Moreover, the distance between the riving knife and the blade would be too high, so the knife would not help too much.
2021’s Best Riving Knives
- Delta 78-965
This riving knife tool is a great complement to any table saw. It weighs slightly more than 10 ounces and is simple to install even if you have no prior knowledge.
When purchasing a new riving knife, be certain that the spacing between the holes is correct. This type is best suited for saws of the latest generation. It also works well with several thin-kerf blades.
The riving knife should be the same thickness as the blade. This variant has a thickness of 0.08 inches and is compatible with most kerf blades.
- Easy to install
- Durable design
- Fits most kerf blades
- Ideal for new generation saws
- Not the best choice for older saws
- Jet 708683
Jet’s riving knife provides no space for ambiguity. The knife has a 0.1-inch thickness and a maximum blade diameter of 10 inches.
No more kerf waste
The knife is ideal for thin blades since it reduces kerf waste. It is ideal for even the tiniest blades.
The most difficult component is fitting it on the blade since you must verify the size is correct. If you do it correctly, the riving knife will endure for a long time.
- Excellent for lots of thin blades
- Durable design
- Great at reducing kickback
- A little challenging to install
- Makita 345940-8
Makita’s original approved component will fit a wide range of proprietary models perfectly. It may also work with saws from other manufacturers.
Check your Makita saw to see what components are compatible with it for the best efficiency. It will work with the majority of current saws.
This riving knife, like anything else from Makita, will amaze with its sturdy construction. Because it is heavier than typical, it is likely to last for a long time.
- High-quality build
- Compatible with many Makita saws
- Suitable to other saws too
- Durable design
- A bit difficult to install
So, what exactly is a riving knife? The riving knife is primarily used for safety and protection. It will eliminate the majority of hazards, but it will also increase your working efficiency in the long run.