Small Pieces - Kickback

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RFGuy
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Re: Small Pieces - Kickback

Post by RFGuy »

JPG wrote: Sat Jul 09, 2022 11:12 am Best advice given - Think through the operation before proceeding!!

Assume the worst WILL happen and adjust procedure to minimize the likelihood of it occurring.

THINK
JPG,

True for many activities (not just woodworking) and I agree with you. The times where I have had an accident are usually because my head wasn't clear or I tried to rush something. Just want to point out that the OP of this thread mentioned that he was new to woodworking AND had a kickback. That is why some of us gave additional advice related to this. I guess the question is really whether a new woodworker gets ALL of the info they need to be safe and successful in reading and following the owner's manual...or is there more training/learning necessary for example to avoid a kickback or some other calamity? How many newbie woodworkers understand and know why they had a kickback? My point being is often a newbie doesn't know what they don't know. Hence this thread and this forum category titled "Beginning Woodworking" right?
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edma194
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Re: Small Pieces - Kickback

Post by edma194 »

New woodworkers have to be introduced to kickback with more than an ambiguous warning to avoid kickback. It isn't just cutoff pieces of wood shooting backward from the blade, kickback can send wood in flying in every direction. Pieces can ricochet off the blade, guard, fence, or your head. Kickback doesn't just affect pieces cut off, it can knock the piece you are holding in any direction, and it can do this all before a piece is cut through, or just break the piece so that any or all of it can be sent flying in multiple pieces and even getting ripped out of your hands. And even if you avoid getting injured by wood projectiles you may have ruined the piece you are working on.

We avoid kickback by being aware of it and gaining experience. We don't simply imagine a piece of wood smoothly sliding across the blade, we also imagined what is happening to the cutoff piece, how the piece is held, and where our hands, body, and head will be relative to the wood. It comes naturally once you're aware of it, and hopefully when happens anyway the steps taken will prevent injury.
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RFGuy
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Re: Small Pieces - Kickback

Post by RFGuy »

edma194 wrote: Sat Jul 09, 2022 12:07 pm We avoid kickback by being aware of it and gaining experience. We don't simply imagine a piece of wood smoothly sliding across the blade, we also imagined what is happening to the cutoff piece, how the piece is held, and where our hands, body, and head will be relative to the wood. It comes naturally once you're aware of it, and hopefully when happens anyway the steps taken will prevent injury.
Ed,

Sorry, but I have to disagree with this one. There are multiple avenues for a kickback and it can happen on just about any woodworking tool, not just tablesaw. They happen so fast that many woodworkers are left dumbfounded after they occur. I mean there isn't a high speed playback you can review afterwards. Speaking just about tablesaw mode, the most common one, I believe, is when the workpiece gets pinched between the sawblade and the fence due to a smaller gap at the rear of the sawblade. In my opinion, this isn't taught or illustrated enough in woodworking circles. Once you see a picture of this kickback, or an animation, it is clear though. I am having a hard time comprehending how a newbie woodworker will "imagine" what is happening in a kickback scenario and "naturally" adjusting their technique with time. What you are suggesting is that newbie woodworkers have to get bitten by the kickback bug and eventually will learn and adapt. That is just too dangerous in my opinion...
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Re: Small Pieces - Kickback

Post by DLB »

RFGuy wrote: Sat Jul 09, 2022 12:19 pm ...Speaking just about tablesaw mode, the most common one, I believe, is when the workpiece gets pinched between the sawblade and the fence due to a smaller gap at the rear of the sawblade. In my opinion, this isn't taught or illustrated enough in woodworking circles. Once you see a picture of this kickback, or an animation, it is clear though. I am having a hard time comprehending how a newbie woodworker will "imagine" what is happening in a kickback scenario and "naturally" adjusting their technique with time. What you are suggesting is that newbie woodworkers have to get bitten by the kickback bug and eventually will learn and adapt. That is just too dangerous in my opinion...
Please explain what you mean by the highlighted part. Are you talking about a case where alignment is sufficiently bad that the workpiece is pinched between rip fence and blade body? Or suggesting that the system must always be aligned such that whatever error is left MUST be in the direction leaving a larger space between fence and blade at the rear Vs. the front?

- David
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Re: Small Pieces - Kickback

Post by edflorence »

I was trying to push a 3" length of mesquite through the band saw with a board. Circumference PARALLEL to the blade. Sure enough, it got spinning and took off! I still haven't found it.

The final straw was trying to cut the 1/2" piece off the mesquite. I wish I'd gotten to the switch earlier, but it wasn't worth getting in front of a potential kickback that DID become a kickback. That prompted my post.
Just to take a moment to return to the bandsaw part of this discussion...you were on the right track, imho, by trying to do this cut on the bandsaw rather than the tablesaw. As you learned, free-handing a cross-cut on a circular workpiece on the bandsaw will literally get out of hand in a heartbeat. However, there are a couple of ways to make this cut safely...1) use the miter gage and clamp the round piece firmly to the face of the gauge...you might have to put an extension on the gauge. Or, 2) make a V-shaped block, like a cradle for the workpiece and either clamp the piece to the cradle or use the miter gage to push workpiece and cradle together through the bandsaw blade. Either method is safer than using the table saw for this kind of cut. I have used method 1) to cross-cut irregular limbs up to about 4 inches in diameter.

As far as not getting to the switch in time to prevent a kickback of a small cut-off trapped inside the upper guard, you might consider adding a foot switch to the system. Shopsmith sells one and it is well worth having. It comes in handy often when making table saw cuts that leave you far from the headstock switch at the end of the cut, and also for routing with the speed increaser.

And, as others have said, read Power Tool Woodworking for Everyone, and any book you can find by Nick Engler.

Stay safe,
Ed
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Re: Small Pieces - Kickback

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DLB wrote: Sat Jul 09, 2022 1:16 pm Please explain what you mean by the highlighted part. Are you talking about a case where alignment is sufficiently bad that the workpiece is pinched between rip fence and blade body? Or suggesting that the system must always be aligned such that whatever error is left MUST be in the direction leaving a larger space between fence and blade at the rear Vs. the front?

- David
David,

Thanks. The alignment doesn't even have to be that "bad". I am trying to find the video that I saw in the past for this. If I find it, I will update this post with it. Below is a Woodcraft article that discusses what I mentioned. They call it "toed-in", but yes it is where there is a larger space at the rear of the sawblade compared to the front between the sawblade and the rip fence. The pictures in the video I am trying to find really illustrated the concept well. I have also seen multiple online woodworking guys talk about this in the past, such as the Wood Whisperer, where they suggest that the rip fence always be aligned to either be exactly parallel with the sawblade at a minimum or better yet purposely set a small (few thou) misalignment at the rear to ensure the workpiece never gets pinched. Basically you never want that "toed-in" rip fence alignment condition. Of course, the OP of this thread had a kickback, I believe, where he was doing a crosscut with the miter gauge so that is a different condition than this.

https://www.woodcraft.com/blog_entries/ ... table-risk

Excerpt from Woodcraft article:
Preventing Kickback
Rip fence alignment

The first step in preventing kickback is aligning your rip fence parallel to your blade. The most serious misalignment is when the fence is “toed-in” toward the blade–meaning that the distance from fence to blade is less at the rear of the blade than at the front. This creates a dangerous funnel effect that causes the edge of a workpiece to press against the rising rear teeth.

To align the fence, mark one tooth, rotate it to the fore, and measure its distance from the fence (Photo A). Next, rotate the tooth aft, and perform the same measurement. (Using the same tooth as a reference removes any blade warp from the equation.) Adjust the fence until the measurements match. If you’re unsure of perfect parallelism, angling the fence outward 1⁄64" or so at the rear of the blade is a safe bet.
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Re: Small Pieces - Kickback

Post by DLB »

I've heard or read the toe-in Vs. toe-out suggestion in several places and am aware of its popularity. I've also read and seen alignment procedures in which the direction of error is ignored and the objective is minimum error. I re-read the attached Woodcraft article (and re-watched the video) and found it compelling with respect to using a riving knife but not with respect to deliberately biasing fence alignment. My least favorite part: "angling the fence outward 1⁄64" or so at the rear of the blade is a safe bet." I don't think it is.

Nick did an excellent video on alignment as discussed in this thread: viewtopic.php?t=28255 In it he explained alignment tolerance as essentially aimed at preventing the workpiece from coming into contact with the blade body. Even ignoring the "or so," a deliberate bias of 1/64" guarantees workpiece contact with the blade body for many (most?) blades. And further guarantees that the rising teeth at the rear of the blade will be widening the kerf and providing an upward force on the workpiece. Assuring the contact only occurs on the side of the blade away from the fence gives me little comfort. My personal preference is to have the fence aligned as precisely to the blade as possible. Then the rear teeth are doing the minimum work widening the kerf and lifting the workpiece. I'm open to being convinced that some "toe-out" bias is better, but I wasn't convinced by this.

- David
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Re: Small Pieces - Kickback

Post by Hobbyman2 »

If I could also add in another issue of vibration / harmonics , on more than one occasion I have watched as a piece vibrated back into the blade and away it went . harmonics and vibration on some saws are much greater than others .
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Re: Small Pieces - Kickback

Post by jsburger »

Lets add another data point to jazz up this discussion. Kick back is more a function of operator error than some kind of misalignment.
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Re: Small Pieces - Kickback

Post by Hobbyman2 »

jsburger wrote: Sat Jul 09, 2022 9:42 pm Lets add another data point to jazz up this discussion. Kick back is more a function of operator error than some kind of misalignment.
------------------

That is a very wide brush . True but a very wide brush .
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