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.
10 thoughts on “Skill Set: Table Saw Safety”
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Kick back can be greatly reduced by never raising the blade more than a couple of mm above the thickness of what you are cutting. This way the arc of the blade does not lift nearly as much and your push stick should be able to mitigate the now nearly total reward force (as opposed to up and rearward).
Related to Jerry’s comment: a good rule of thumb along this line is to set the saw so that the gullet–the curved indent in between the teeth–is at the top of the piece you’re cutting.
A splitter is not truly necessary to prevent kickback. It will prevent the wood from closing on the blade as tensions in the wood are released as it is cut. I have been a professional cabinet and furniture maker for 12 years. I truly believe that what prevents kickback is proper setup of the saw and fixtures and trained hand.
A kickback occurs when something is trapped between blade and fence. You must be vigilant in knowing where your cutoffs will end up and where you will be at the end of the cut as that is where a kickback will usually happen.
Also a note is the importance of pushblocks. Something to keep your hand away and above the blade. And if properly made they can give you much more control and allow you to cut very small pieces.
The following is a list of reasons that stock can kick back:
1. Crosscutting a piece of wood with the miter gauge on the left side
of the blade while the fence is being used as a stop on the righthand
side of the blade – blam-o!
2. In some cases kickback is created if the saw kerf closes around the blade.
3. Make sure the fence is parallel to the blade. If the fence is toed
inward toward the blade, it can cause the wood to come in contact with
the back edge of the blade.
4. Cutting twisted, distorted, knotty, crooked or springy wood.
5. Freehand cutting or cutting wood that is not flat on the table, such as round stock.
6. Losing control of the work or letting go of the wood at the same time it’s in contact with the saw blade.
7. Not following through when ripping, or stopping before the cut is complete.
8. Intentionally or unintentionally allowing the wood to “drop” on top or to the side of the back of the blade.
9. Backing out of a cut.
10. Improper setup of the machine’s guards, fixtures or hold-downs.
11. Applying the entire pushing force toward the off-fall or free section of the work instead of pushing toward the fence.
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Yes a agree with Nick that splitter is not truly necessary to prevent kickback. I found very good reviews about table saw reviews and I decided to buy Ridgid R4510.