Woodworking Essentials: Table Saws
Fourth is how to control oversized material. Large and heavy wood can have a tendency to tip or fall off the machine. It’s very hard to control large and awkward stock. I know most shops are limited on space, but it sure is nice to have extra table surfaces around the sides and especially the back of the saw. If you have someone helping you with large stock, make sure you practice first and make sure you are in control of the cut. The helper should just act as a table extension. It does not work to have two people trying to steer a piece of wood through the saw at the same time. If a helper is not available, use a roller support to help support long stock as it is being ripped.
The fifth factor of control on a table saw is the feed rate. The rate you feed the stock in the cut can be affected by many factors including the differences between ripping and crosscutting, the type of blade being used and its sharpness, the type of material being cut, and the power of the saw. Sometimes just listening to the cut will tell you more than anything else. You should never force the cut to the point where the blade stalls. If you notice the edge of the board is burning, that’s a pretty good indication that you are feeding too slowly, that your blade is dull or that the fence is misaligned – or possibly all three. If the edges of your boards are showing signs of burning, try to speed up the feed rate a bit. If that doesn’t improve the burning then the blade is probably getting dull or needs a good cleaning. Verify that the fence is parallel to the blade.
And finally, the sixth factor of control is built into the saw itself. On a 10″ table saw the blade is rotating at approximately 4,000 rpm. As wood makes initial contact with the blade there is little kicking force because the cutting force is straight down toward the table, just like with a band saw. As the wood continues in the cut to a point where the stock is about halfway past the blade, the wood will start to encounter a forward vector of force that in turn will cause the wood to react by moving in the direction of the rotating blade or toward the operator (the action of kickback will be explained in my next article). To counter these forces, engineers have built in “control” as a way to manage the undesirable effects of the wood when it contacts the blade. The table itself, the fence, a miter gauge, standard guarding, specialty devices such as push sticks, featherboards and hold-down devices, are all great ways to control the stock as it meets the point of contact on a rotating blade. A well-designed machine provides or has available some type of “control” to counter the kicking and grabbing forces that naturally take place with rotating cutters and provides the user with a clear range of motion through the entire process.
Three Kinds of Exposure
Going back to Winters’ explanation of hazard and exposure, he says that by reducing the exposure, you will reduce the danger level. Less exposure means less danger; more exposure means more danger. It almost doesn’t get easier than that – and that should be the golden rule of operating all power equipment in the shop safely. Exposure at a table saw can have three meanings: blade height when there is no guard being used, blade height with the guard and repetitiveness. (For the sake of argument let’s just say that these rules apply to all blade types.)
Blade Height when No Guard is Used
Let’s face it: No matter what rules we establish for the table saw when it comes to using your guard, most woodworkers, both professional and novice, will at some time remove the guard(s) to make certain types of cuts. Nothing good comes by removing a guard. If you violate my rules about never running a table saw without a guard, then you must set some kind of rule as to how much blade exposure you will allow. With unguarded and exposed through cuts the best rule to use is “minimize, not maximize.” Like the late Dr. Roger Cliffe used to say, “How high the blade should be above your work is a definition of terms: the difference between amputation and laceration.” And if the blade is unguarded you might as well plan on both kickback and blade contact as a part of your future.
It is recommended that when you are making unguarded through-cuts that the blade be set about 1/8″ to 1/4″ above the stock. However, keep this in mind: At a lower blade setting there are a considerable number of teeth in the cut that are moving in a substantially forward direction. Kickback forces can be transferred into the wood most efficiently with a low blade, and with a lower blade there is a greater distance between the rear of the blade and the splitter. Plus more teeth means more friction, which in turn heats the blade and increases the risk of burning the wood.
Let’s just make this whole issue simple: Always find a way to guard the blade; never use a table saw without the guard. The point of the two photos above right is to demonstrate that at the low blade exposure, the blade will have three teeth in the work at the rear of the blade. At full exposure, only two rear teeth are in the work. The trajectory at the low setting will have the teeth of the blade leaning 60° off vertical, directed at the operator while at full exposure, the trajectory of the teeth is only 30° off vertical.
Blade Height when Guard is Used
This may take you by surprise but a higher blade height helps the blade to run cooler. At the same time, it helps the motor to run more efficiently while using less power. I’ve been told that if the saw is adjusted just right, you will also get a cleaner cut with a higher blade. This is why at trade shows you always see the “pitch man” running the blade as high as possible when demonstrating his blades. Why don’t they use their guards – bunch of dummies!?!
Think of this as well: With fewer teeth in the cut, the transfer of forward energy is less efficient and a higher blade presents less of a gap between itself and the splitter. All of a sudden, it sounds like I’m recommending that you run your blade as high as possible, but that’s not the case. Keep in mind that a higher blade setting produces more exposure and a greater danger level – only if the guard is not in place. And this discussion is about blade height with the guards in place. With a guard acting like a barrier, the likelihood of the blade contacting your hand(s) from any direction, except straight in, is low. No pivoted or aftermarket guard can prevent you from sliding your hand straight into the blade. So what’s the answer? The answer is that a well-guarded blade can be set slightly higher than an unguarded blade.
The second type of exposure is in terms of repetitiveness. Each time you make multiple cuts or passes you could be putting yourself at more risk. For example, there is no sense in making several passes over a table saw blade to make a wide cut when you could have done it in one pass with a dado blade. As you present yourself to extra passes or multiple moves, you expose yourself to more risk.