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Kickback explained and contained!

2.8K views 17 replies 11 participants last post by  J_L  
#1 ·
Finally a video explaining the how and the why of kickback, and of course the answer is Physics:
 
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#2 ·
I have seen similar kickback demonstrations. What impressed me the most in this video was their clever setup that showed kickbacks in real wood, not soft foam.

Another thing that interested me was seeing the vibrations and reverberations of the blade and throat plate in the slow motion videos. It shows that objects that you imagine to be very rigid are not.
 
#3 ·
Most (all?) of the kickbacks in the video happened when the work piece rotated and was snagged by the teeth at the rear, as they are coming up. But don't some kinds of kick backs happen on the front of the blade? Like if the wood is pushed too fast, the teeth take too big of a bite and instead of cutting they throw the wood? Or the work piece lifts from the table and teeth at the top catch the wood?
 
#4 ·
this video was allowed here for safety information only - this forum does not endorse any of the products used in the video. use all power tools at your discretion and within your skill sets. removing or altering any safety feature on any power tool is done so at your own risk of bodily injury or death. ensure that you know and understand everything about your power tool prior to operation.
 
#5 · (Edited)
Thanks, guys. I didn't watch the entire video, so I wasn't aware of any ad content. I just liked what I saw early in and agreed with the demo. I would add to that., I strongly oppose the use of a narrow, "one point of contact push stick" as shown in the video. I have been advocating using a "push shoe" here for many years because it allows for forward, downward and lateral pressure towards the fence on the workpiece, in other words, "far more control" .
This old video is one of my favorites showing what causes kickback:
Best kickback Video I've seen:
 
#8 ·
I didn't watch the entire video
Just as a general unspoken rule, guys, it's best to watch the entire video when you post someone else's work because you never know what hidden 'gems' lie in wait. In this case you knew right away who sponsored the video and that some sort of plug was coming so it wasn't a surprise.
 
#7 · (Edited)
I use a push...thing I guess a lot of people use, basically a piece with a handle, hook in the back and the front extends out to put pressure downward on the work piece .. Maybe I've been extremely lucky in that I've had very few kickbacks and only one that hit me to leave a red mark for a few minutes.. The push stick that comes with the saw always feels kind of useless. I'm not sure I've even gotten my DNA on it yet.
As for my hands going over the blade it doesn't take a lot of cutting yourselves with saw blades to figure out how not to put your hands above the blade. Personally I prefer beside the blade over above the blade. I can't think of too many reasons to have your hand directly above one other than perhaps cutting rabbits on wide pieces where there's plenty of room..
 
#12 ·
There are two things to think about when using push sticks.

There is no reason that you can not use TWO push sticks simultaneously, one for pushing and down pressure, the other for sideways pressure.

Push sticks are intended to be cut by the saw and should be considered disposable.

BTW - The opening sequence in the video, IMNSHO, shows the absolutely wrong way to use a push stick. (Plastic or otherwise.) The push stick should be pushing the stock through the cut and should be as close to the blade as possible.
 
#14 · (Edited)
Rather than a second push stick, why not a featherboard in front of the blade to hold the work against the fence. Push sticks can slide when used at an angle and then what happens? It's up to you how you maintain the three forces, downward, forward and against the fence, but a push shoe that has at least 6" of contact will do all three. Once the wood kerf engages the splitter, you are fairly safe against it coming away from the fence.

I liked the part in the first video where he stated there are 50,000 table saw injuries and described both types, blade contact and kickback. I'll wager there are far more kickback injuries than are ever reported. I know I am the only person who ever knew about mine! They were never severe enough to draw blood or need an ER visit, so they were never documented and I'll bet there are thousands of others like me.

For you guys that like 2 narrow push sticks, just try a push shoe and then see how you feel about them.
Just in case I haven't made it perfectly clear, being able to apply the lateral pressure holding the workpiece against the fence is the key to preventing the most common type of kickback!
Using 2 narrow push sticks may accomplish that, BUT you do need 2 not just one!

Of all those shown there are only two that are really ergonomically the best shape.
This video has the best shape for applying the 3 types of pressure, downward, forward and laterally towards the fence. Those with a tall vertical handle ignore how your wrist applies force, downward force yes, but completely unstable side to side. They are worthless in my opinion. It's always about the physics and ergonomics!
 
#17 ·
Here's a video about different style push sticks. Like most others, I dislike the short push stick. They're dangerous because of the lack of control. The larger push "shoe" style is much safer.

In the intro photo there's a push shoe with a tall, angled handle that you grip like a handsaw or a pistol. This is NOT ergonomically a good design, JMO and here's why.
It's difficult to keep vertical while also applying downward and forward pressure, because it wants to tip to one side or the other. Your wrist normally will twist when held at that angle and with that grip. Orient your wrist straight out and point you forefinger finger in the direction you are pushing. You'll see that you have much greater control that way. I recommend the design in the April Wilkerson video. BUT don't take my word for it, try that type and see how you like it!
 
#16 ·
Attached are three pages from a ShopSmith / a Time Life Book on jigs, showing how to make a push stick.

The great thing about this push stick / block / thingamajig is that the disposable parts are simple, 2 x 4 and ÂĽ sheet material scrap. I made mine (4 or 5) from 2 pieces of glued up Âľ Baltic Birch.

Once you make these you'll wonder how you got by without for so long. IMO Best push stick ever.

BTW - I use a Kreg screw to hold everything together. The longer the better. Avoid flat head screws.

Also the plan is in the Taunton book "In the Craftsman style" somewhere near page 60.
 

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#18 ·
The taller, angled handle for the push shoe is ONLY used on narrow rips when an overblade guard is in place. It is tall enough to clear the guard (which April's will not do). That is the only time I use this style. Otherwise, my favorite style is similar to April's but quick to make and disposable after I've ran it through the blade too many times. I normally have half a dozen of these floating around the shop including two stuck to my saw with magnets embedded in them.