What causes kickback?

kickbackBang! Suddenly, the saw is throwing lumber at you! Your risk is related to how you feed the board. Stand out of its direct path. Operating a table saw this way might not be intuitive, but it helps you avoid kickback. The blade cuts going down in front, but remember the heel comes simultaneously upward. The back end should have a clear path upward, but sometimes it touches. The heel is capable of grabbing lumber, carrying it up and throwing it over toward you, so make it your goal to prevent the heel from touching.

normal saw feed directionFeed direction ordinarily goes the opposite of rotation direction. Table saw feed direction is against the way the saw is turning. The rotation direction of a table saw is toward the front. It cuts downward, thus the way a blade faces is normally opposite to feed. A portable circular saw cutting upward can be thought of the same but upside down.

Feeding in reverse risks letting the wood kick back, so cutting along with the rotation direction, or climbing, is not casually contemplated in a manual operation. With power feed, conveyors and rollers hold the boards and glide them through. When human involvement is minimized, the option of climb cutting becomes possible.

Grabbing

saw climb cuttingAn overhead radial arm saw crosscuts by climb cutting. It needs to be carefully adjusted for avoiding the danger of jumping toward you. A miter saw can grab if the blade is too eager instead of neutral. To reduce grabbing, the blade on an overhead saw should have negative hook. Do not rip on a radial arm saw unless you lock the head parallel to the fence and notice which way it turns. Ripping is done by pushing the work contrary to the turning. If you were letting it feed as it wanted, you'd feel it pulling. That might seem easier, but it's inviting the menacing risk that it could throw the work.

Hold down

A panel must be held flat on a table saw. Use a long notched push stick. Push a plank completely through from front to rear. If a loose scrap is left adjacent to the blade, leaving it running as you retrieve it would be taking chances. First turn it off and then discard the waste.

To cut thin plywood, it seems logical to lower a blade. However, if it is set too low, flexible panels may ride up. If the rim is mostly in the cut, it aims horizontally to the front. If you raise it so it cuts downward, it helps you keep the work flat. If overfeeding happens, slamming the wood down again is courting disaster. That would be jamming it deliberately. Instead, stop pushing and ease back before it binds up.

A featherboard can be put vertically on the fence to hold down the material, and a horizontal one positioned at the front of the table to push toward the fence. It has springy fingers stopping any motion in reverse to the feed direction. This can be homemade.

Binding

Trimming the ends of long boards is a difficult task to manage without rocking. As you prepare to cut an unwieldy sheet, stabilize it so it cannot lift up or sink as you cut it apart. The table is like a fulcrum. If the plank hangs down at the far end, then the bottom edge of the cut rises up. If you let it gradually pinch together, it will kick back.

Immobilizing the panel is also important for a skilsaw. If you simply balance the wood on two supports and cut between them, the weight of the skilsaw may push down until it causes binding at the top edge of the cut. Ideally the wood should be as well supported after cutting as it was before, so none of it can pivot or sag.

Unseasoned, green lumber with high moisture content could twist and bind up. Use a stiff, coarse blade for avoiding binding in such conditions. Don't use a blade that is too fine, which could bind as badly as one that is dulled. As you rip a board, the cut may squeeze back together again after it passes through. If the wood binds up enough against the heel, it gets thrust upward. Putting a spreader, splitter or riving knife just behind the heel can stop pinching. It is thicker than the plate but thinner than the kerf. An off feed extension is helpful for ripping.

When you use a fence, align the rear just barely away. This shortens the area of tight contact and helps avoid trapping narrow strips that could bind up between. If you tilt it to cut bevels, set it up so as not to trap the lower section. When you use a miter gauge, the fence is unnecessary. Periodically wax surfaces to make them slippery to lessen binding. Use a circular saw to cut straight lines, but not for curvilinear shapes. A bandsaw is an appropriate alternative for those.

Stalling

Some portable circular saws lack steady momentum and may stall. At that moment, it could grab and try to take too great a bite. Trying to do things in a hurry might cause stalling. Once it bogs, jamming is imminent but not inevitable. Be alert and listen for struggling, so you can ease up to compensate. On a lightweight model, raise a blade higher to help minimize drag. A bent tip dramatically increases drag. Buzzing or messy cuts give you a warning.

Anti-kickback blades

In gutting or remodeling, you may hit metal fasteners and other surprises. To absorb the shock, anti-kickback blades are tough. The rim is stiff and raised all around to prohibit overfeeding and jamming. If the spacing is very coarse, intermediate bumps or fins may be added to inhibit grabbing. They don't stop binding or pinching, so stay prepared.