In response to our post Woodworking Tips from Laura’s Dad, there were several comments about author Craig Cochrane’s table saw not having a splitter on it to help prevent kickbacks, which can be dangerous. One reader, Mark Harrison, recommended a couple of table saw basics and safety articles on Popular Woodworking’s website. Here’s a link to them. Thanks, Mark!
The Mechanics of Kickback
Kickback occurs when a piece of wood is unexpectedly thrown back toward the operator. The lifting and throwing force of kickback starts at the back of the blade, not the front.
To get a better understanding of how this force is created, unplug your saw and mark any tooth with a felt-tip marker. Now rotate that tooth to where it just starts to rise above the table at the back of your saw’s throat plate.
If you follow this one tooth as it rotates it will give you a better idea how a piece of wood is lifted and thrown forward. When the blade rises through the table at the back of the saw it has an initial vertical lift. As the blade continues to rotate and reaches the top of its arc, the vertical lift begins to transform into a horizontal thrust. By the time the blade moves from the top of the arc back down toward the saw’s table, the horizontal thrust transitions back to vertical. By now all the force is moving down towards the table on its way to doing it all over again.
To help students understand how much lift a rotating blade has, I move them over to the 20″ disc sander (unplugged, of course). As the sandpaper disc rotates, you can safely sand wood on the side that is rotating down toward the table. But move the wood to the lifting side and the piece is immediately lifted up. A table saw blade works in a similar fashion.