What causes kickback?
The most common cause of accidents is kickback. Kickback occurs when the top quarter of the saw blade, also known as the kickback zone, contacts a solid object (wood or metal). Because the cutter is coming down the edge of the saw bar in the kickback zone, the depth gauge is lower than it should be in relation to the tooth. Literally, the saw bites off more than it can chew, stopping or slowing the chain. The result is a rotational force that flings the bar backward, into the operator. When the bar rears back, the chain break will be activated and stop the chain in 1/55th of second. The saw may still strike you, but the chain is not rotating and the damage will not be as severe.
DO NOT USE THE KICKBACK ZONE AND ALWAYS BE AWARE OF ITS LOCATION!!!
Low Kickback Chains (aka Safety Chains)
Low kickback chains are commonly found on saws for homeowners and are standard equipment on many new saws. As you can see from the picture, low kickback chains have an additional depth gauge between the cutters. The extra depth gauge is either the result of a special drive link (called a bumper drive link) or putting a bumper on the tie straps.
The depth gauge sets the depth or thickness of the chip produced by the cutting corner of the cutter. The depth gauge is an important safety feature. The thicker the chip, the more severe the potential kickback. By regulating chip size, depth gauges also regulate the severity of reactive forces.
- Low kickback chains really do reduce kickback, but they’re not popular with professionals for two reasons.
If you’re felling trees, it makes a bore cut nearly impossible. The bore cut is a safety technique that minimizes the possibility of getting injured or killed by the barber chair or stump jump. Because the upper half of the bar tip won’t cut well, bore cuts go very slowly.
- If you sharpen the chain yourself, a safety chain can be more difficult to sharpen. This isn’t a problem if you take your chain to a dealer to sharpen.
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