Can a sliding miter saw cause kickback? Yes, in a sense. Many woodworkers are familiar with the unnerving experience of having a sliding miter saw blade bind in piece of wood; in the middle of a cut, you feel a sudden, violent jerking backward of the motor and blade unit. Such an event is not as likely as other forms of kickback to cause serious injury, but it can leave the operator with a desire to move on to something safer – like sanding or sweeping the floor.
In most cases, the term "kickback" relates to stationary woodworking machinery, which is typically much more powerful than a sliding miter saw. True kickback happens when the blade or cutter of a woodworking machine binds on a piece of stock and hurts it back in the direction of the operator. In comparison to miter saw kickback, this is a much more serious situation. The sudden motion can draw your hand into contact with the bit or blade. Or, in a worst case scenario, you could have stuck or impaled with the flung-back piece of stock.
With a sliding miter saw, "kickback" occurs when the blade gets hung up on the material during the cut. If the material is tight up against the saw's fence – as it should be – the result will be a sudden force propelling the saw motor and blade assembly outwards toward the user. While this is definitely starting, it usually does not lead to serious consequences – provided the operator is following basic safety procedures.
Even if you do follow basic miter saw safety rules – keeping your free hand well out of the path of the blade; wearing safety equipment; making sure any angle settings are securely locked in; keeping the material up tight against the fence and bed of the tool, etc. (refer to your saw's owner's manual for a more complete list) – you may encounter this occasional surprise. The most common is the one described above, where the blade gets stuck in the material and, in the case of a sliding saw, is propelled toward the user.
What causes this? Miter saw kickback happens when the kerf (the slot made by the blade) closes in on the blade and "grabs" it. It happens frequently when crosscutting long, wide boards near the middle. When lumber is not perfectly straight and flat, it can not be held in firm contact with the fence and bed of the saw at every point. As the cut proceeds and the wood moves into closer contact with the fence and / or bed, the kerf changes shape and can impinge on the path of the blade. When cutting long, wide stock on a sliding miter saw, some woodworkers like to start by making a partial chop cut near the fence side of the blade. Doing this helps soften the effects of any binding that takes place.
Other factors contribute to blade binding, including one or two that are absolutely preventable. Wet wood or wood with a high pitch content is more "sticky" and can be more grab-prone. A dull or inappropriate blade will also have more of a tendency to bind. On a sliding miter saw, a dull blade with an aggressive hook angle and too few teeth is a recipe for jagged cuts, short bits of cutoff ricocheting hither and yon, and a generally unpleasing sawing experience at the very least. A quality blade designed for use on a miter saw will not only help cut down on binding, but will also make a world of difference in quality of cut the saw deliveries.
You should also check to make sure the saw is functioning properly. The blade needs follow a perfectly straight path through the cut to avoid rubbing up against the kerf. Make sure that bevel and miter settings are holding fast, that the blade is on tight, and that there's no appreciable slop in any of the working parts.
It's a good idea to make sure that the two sides of the fence are on the same plane. If they are not, and the fence is not adjustable, the problem can be corrected by adding a shop-made sub-fence to ether side and shimming until the two are exactly coplanar. If all is working correctly and you are using a sharp, appropriate blade, the vast majority of your cuts should be near glass smooth and trouble free.
Another unpleaser miter saw event happens when the blade catches the edge of a piece of cutoff and fires it across the shop. Occurring most often with very small pieces of stock, this type of "kickback" is rarely puts the operator in great physical danger (as long as appropriate safety equipment is in use). But it is startling, and can be very annoying when the sawn-off projectile – which can be extremely difficult to find – is the part you need.
A good blade and a correctly functioning saw are the best defense against flying cutoff. It's also advisable to use a moderate slicing stroke instead of slamming though the wood as fast as you can (chop saw is a name, after all, not an instruction). Another trick is to let the blade come to a complete stop before lifting it up past the stock. If everything else is in order, doing so should leave even tiny cut off ends lying right next to the blade.
by Jim Soderberg