Woodworking Essentials: Table Saws
Splitter The second guard on a table saw is not quite as obvious as the enclosure or top guard but is the most important part of the guarding system. The splitter, sometimes referred to as a spreader or riving knife, is directly behind the blade and is used for through cuts. Splitters are most effective when they are the exact width as the kerf of the blade and are in perfect alignment with it. The splitter separates and prevents material that is being cut from coming in contact with the back of the blade. That minimizes the chance of pinching and kicking back. Typical American- made splitters will not work for non-through cuts, which will require that they be removed. It is important to realize that even with a splitter properly installed, kickback can occur if through some circumstance the wood should make contact with the back or top of the blade and just before the splitter. Be aware that the closer the splitter is to the blade, the more effective it will be. Splitters should be used for both ripping and crosscutting.
There are two types of splitters – static and dynamic. Today nearly all American-made contractor and cabinet saws have static splitters (though that is changing). These are the typical top guard/splitter/anti-kickback-finger combination-guard system that comes with most new saws. This combination guard system is attached just behind the blade arbor and just to the back of the saw table. They do not move once they are installed. Standard splitter/guard systems can vary in how close the splitter is located to the blade, but can be as far back as 2″ or more. The larger the gap between the splitter and the blade, the more potential there is for a piece of stock to come in contact with the back of the blade. Be mindful that with a static splitter, the gap will vary as the blade is raised and lowered. Static splitters must also be removed when making non-through cuts.
A better type of splitter is one that is not connected to the enclosure or top guard, but is connected to the arbor casting itself. On European saws this type of splitter is called a riving knife. It is located just barely behind the blade and will raise and lower with the blade. The gap between the two never changes and is typically as close as 1⁄4″. A good riving knife is set just a little lower in height than the arc of the blade. This allows you to make both through and non-through cuts, which makes you safer and more productive. Riving knives should not be used with dado or moulding-head cutters. For the record, I would much rather have a riving-knife type of splitter on my saw.
Anti-kickback fingers are sometimes referred to as non-kickback fingers, dogs or pawls. Their job is to oppose the tendency of the saw to pick up material and throw it toward the operator. Overall, I’m all for any thing that can make a saw safer. From an engineering point of view, anti-kickback fingers seem to be a good concept but they come with quite a bit of controversy as to their effectiveness. European saw manufacturers don’t use them at all because they deem them to be virtually ineffective with little positive gain. As a matter of fact, European saws can’t have anti-kickback fingers because of the dynamics of a riving knife. Anti-kickback fingers can sometimes get in the way. For example they can limit and even interfere when ripping narrow stock. I’ve had on numerous occasions the anti-kickback finger limit the motion and even obstruct my push stick.
A splitter is a nice safety addition to a crosscut sled. However, you will have to remove your anti-kickback fingers if you use a splitter with your crosscut sled because they will create a hang up when you pull the sled back after the cut. Although anti-kickback fingers do work when using a miter gauge for crosscutting, they are virtually useless with stock less than 6″ wide. Remember: A standard guard/splitter combination is set back from the blade, which causes the anti-kickback fingers to be positioned even farther from the back of the blade. When crosscutting, the cut is completed when the trailing edge of the board clears the front of the teeth. This will leave the unsupported cut-off board right next to the back portion of the blade and just before the anti-kickback fingers. Because anti-kickback fingers are attached to the splitter, they follow the same rule for through and non-through cut applications as the splitter.
In the next issue I’ll be discussing in detail one of the most serious safety problems with table saws: kickback. And I’ll discuss how you can prevent it. PW