Learn from my kickback event.

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I've used my Delta Unisaw as a hobbyist for 10 years and never had a kickback--until yesterday.
I was ripping a piece of oak about 8 inches wide and 20 in. long. I was using a blade guard with integrated splitter and anti-kickback pawls. I had a horizontal featherboard holding the workpiece against the fence. The offcut was about 1/4 in. wide. The rip cut was complete and I was pushing the workpiece past the blade when I heard a loud whap! and felt something hit me me hard just below the belt. The offcut piece had been caught by the blade and turned into an arrow. I was only bruised but I know it could have been a lot worse.
Somehow the anti-kickback pawl was not properly engaging the offcut piece. The pawl is easily deflected sideways and an offcut piece only 1/4 in. wide can easily slip to either side of the pawl, entirely escaping it's grip. The offcut piece must have flopped around enough to get caught by the blade. The workpiece between the blade and the fence remained where it should be.
I'm not sure what to do to keep a thin offcut piece from getting caught by the blade but I've learned two lessons:
1) Like the safety books say, keep your body out of the plane of the blade. I usually do this, but "usually" doesn't help when kickback happens.
2) Accidents can happen when you least expect it. Just before I started the cut I thought "This cut is properly set up--lots of safety here." I felt safe, but breaking one safety rule is all it takes.
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If it hadn't happened to you, I would have said it was impossible. I have had the cut piece kickback a couple times (before I bothered with a splitter...) but never the offcut piece. Maybe your featherboard pushed it into the blade, but the splitter should have saved you. Hmm.
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Billy Smith wrote:

<snip>
SFWIW, have a Unifence installed on a contractor's saw.
First thing I did was trash the kick back feature of the factory supplied splitter function.
I use a horizontal feather board as well as a vertical feather board clamped to the UniFence for almost every saw cut.
I like push sticks.
They allow me to observe the cut from afar.
Call me a chicken, but I work alone, and like the single handed sailor, which I am, if I screw up, there is nobody around to help, and I'm probably dead before help finds me.
Who needs Vegas?<G>
Lew
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So, one thought comes to mind... Where was your feather board located relative to the blade? It occurs to me that a 20 inch long board isn't necessarily long enough to allow the offcut to be relaxed and float after passing through the blade. In other words, the side pressure of the featherboard can potentially be enough to encourage the offcut to flex into the blade. Of course, that would only be the case with a decent amount of pressure being applied by the featherboard. What kind of board was it? We've all suffered the issue of internal stresses which persuade lumber to do things we wish it didn't do - maybe that played into the situation. Ok - that's more than one thought.
The one thing that rings loudly though is something that has been said here before - it's not the safety equipment that makes using a saw safe, it's the safety of the operator. All of the gizmos in the world don't replace carefully observing the cut throughout, and until the point where the material is clear of the blade. Kickback is very predictable and there's nothing mysterious about it. Observed, it's always a matter of a cut off riding up the back side of the blade. Watching and actually controlling the stock and the cutoff through the cut is the only thing that will prevent kickback with reliability... or so they say. The problem is - don't we all think we're watching all of those things on every cut? Sooner or later something happens to remind us that there's always something to watch. And of course - it's always so much easier to analyze it after the fact. I am one of the advocates though, that suggests that the more of the "safety gear" we put on our tools, the further we remove ourselves from the fundamentals. We tend to put our trust in the equipement and maybe relax our vigilance. I don't dismiss safety gear, but it's no replacement for paying attention. And of course, there's exactly how many of us here who can't be accused on not having paid compete attention at some time or another???
--

-Mike-
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"Billy Smith" wrote in message

If your gonads don't shrink up a little every time you turn on a spinning blade, you're getting complacent.
--
www.e-woodshop.net
Last update: 10/22/05
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wrote:

[snip]
[snip]
Ayup. That's one reason that I took the pawls off shortly after I set up the saw.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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snipped-for-privacy@milmac.com (Doug Miller) wrote:

To make sure ALL your offcuts escape the pawls?
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No, to avoid having the nearly-useless-to-begin-with pawls push a narrow offcut *into* the blade. Just like what happened to the OP.
--
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Doug Miller (alphageek at milmac dot com)
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wrote:

Reading the OP's original description, that is the first thing I thought too. That the paws pushed the thin cutoff into the blade. I am not too impressed with the paws either. They seem to work ok for wide pieces, but not for thin strips and seem to be problematic as they are loose and tend to be floppy. Easily slipping off or not engaging a narrow cutoff. Chuck
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That was my suspicion as well.
-j
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On Mon, 24 Oct 2005 04:32:49 GMT, "Billy Smith"

I have the same setup (I think). I've been doing a little furring job before hanging some drywall and a neighbor gave me some unused but well seasoned (read twisted) framing lumber. Since it's non-structural, I have been squaring it up some on the jointer and taking a thin cut on the TS.
The offcuts pften come zipping back toward the front of the saw, for the same reason you've seen; they're thin and flexible and get back into the blade and are not engaged by the anti-kickback pawl.
But I'm not standing over there, I'm completely to the right of the fence; the only safe place to be.
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Those thin pieces can sometimes get behind the kickback pawls on some guards. I have seen it happen, but no kickbacks.
Those small pieces can indeed become an arrow. I posted here several months ago about my son's friend who was impaled by thin stock that flew back from a planer. He survived but did a lot of hospital time.
RonB
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Glad to hear you didn't suffer a serious injury and thanks for the reminder.
Hindsight is always 20/20, but I assume the blade was not very high? I'm wondering if the blade was set high if the blade would be less likely to fling it. Of course, I don't know if there would be much tear out on the underside of your cut. Also, with a tall blade there is still the possibility of grabbing the "arrow" unless a board was above it from preventing it from rising.
Jeff
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In order to apply horizontal force to the workpiece but not the blade, I always position the horizontal featherboard so that the tip closest to the blade is about an inch away from the blade.
I have tested the anti-kickback pawls before and found them to be pretty effective. But that was with at least an inch or so of board on both sides of the blade so there was plenty of wood for the pawl to catch on. A very thin piece of wood can simply slip between the splitter and the pawl and that's what I think happened.
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The board I was cutting was about 1/2 in thick and I set the blade so that the teeth just broke the surface, so the blade was pretty low. The kickback happened just after the cut was completed.
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I still can't see it happening. Even if the cutoff did contact teh blade, which the splitter should have prevented, the blade should have knocked it aside rather than shot it back. Where was your featherboard? Was the cutoff still in contact with it? If so, that would do it.
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The common rule for blade height is a full tooth above the stock. However, when I rip thin stock, I do raise it higher. This helps by reducing blade lift of the workpiece. Although, I've only had one incident of kick-back, 30 years ago, I always wear a leather shop apron. (The Lie-Nielsen is now the only one I use.)
Dave
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Billy Smith wrote:

....
That's a problem imo...the blade should be high enough that the gullet is near the top surface so the teeth clear fully...won't absolutely prevent it but will minimize the likelihood.
That, plus the narrowness of the offcut in this case is such that as you noted elsewhere the pawls are unlikely to be of much value.
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You might be interested to know that the arguments about blade height are rehearsed on my web site - Circular Sawbench Safety - Blades.
Jeff G
--
Jeff Gorman, West Yorkshire, UK
email : Username is amgron
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