Kickback caused by DC/Overhead Guard????

This is a hard one to believe, but I think I've found the cause.... I was building a new sharpening station yesterday (pics on ABPW, btw) when it happened. Just finished the last rip from some 1/4" ply for drawer bottoms when WHAM... the off cut flew out of nowhere and hit me hard just below the beltline. Then, the damn thing bounced off me, flew under the blade guard, hit the blade again, and WHAM, this time it nailed my arm which I'd just put down around the first wound. I powered down and unzipped to check my gut, it's definately gonna leave a mark. There actually a 1/2" hole in my blue jeans where the corner of that 1/4" ply hit me, and a large welt on my arm where it hit me again..... OK.. time to stop and figure out WTF just happened. I have a new 3hp Jet cabinet saw that was been an absolute joy. Recently, I fitted it with an Excalibur overhead blade guard with DC which, by the way, was in use during the cut. The piece of ply was 24" by 20" or so an I was ripping 4" off the 20" side. Only one hand was on the stock, so I didn't bind the blade. But what the #$%^ happened??? Well, I was starting to ache badly, my side and arm, so I opened up a beer, (and another, (etc...) and pondered this for a while. My technique was fine, guard and splitter were in place. What caused this????????? My best theory is that the off cut was actually pulled off the table and into the blade by the suction from the dust collection on the blade guard, which caused the kickback. It didn't take long (another beer) before I unplugged the saw, fired up the DC and started "testing". Going through the motions of the last cut, I discovered that the suction from the DC, when the guard was lowered fully to the table, was enough to pull up my ZCI. It didn't pull it completely out from the saw throat, but it could pull it up enough for the blade to catch it. The DC also had enough suction to pull pieces of the 1/4" ply up off the table, even though the guard was 1/2" or more above the ply. I didn't get very scientific with this test, and by that time I was under the influence, but the conclusion is the DC surely can pull stuff off the table and into the blade. Oddly enough, this experience happened to someone who is in no way accustomed to using a blade guard at all, let alone one with built in DC. I've a nice welt on my arm, and a good sized black and blue mark on my gut from this. I'm certainly gonna continue using the guard, and the DC, but I think the DC certainly will not be used for thinner or smaller materials. Anyone else have an experience like this??? --dave
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Hello Dave, I'm glad to read you are not severely injured. I posted a while back about my table insert being lifted by the basket type guard I had on my saw. Some adhesive from a prior cut (some construction scrap I was using for a makeshift shelf) adhered to the guard and this picked up the insert as I pushed a new piece toward the blade. No damage occurred.
A question to you, or anyone else that does have a vaccuum port on the guard; How noticeable a difference is there if you don't use the guard vacuum hook-up? Does the setup really get rid of that much dust? My saw produces very little dust up top so I don't see the need to have a guard hook-up. Marc
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Yes my Biesemeyer has a dust port. I use a very large Craftsman shop vac and it is very effective.
The dust coming off the blade is generally VERY fine and this is the exact stuff you want to try to capture.
marc rosen wrote:

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Jeez Dave, I am certainly glad to hear that you survived that accident. I have seen that happen before and it's a shame that a guard sometimes is the cause of a problem. The same can happen when small cut off pieces get trapped between the guard and the blade. If you feel safer using the guard, by all means keep using it. I think I would also look into finding a way to anchor the ZCI in place. Perhaps a screw that turns a locking arm under the table top.

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<...snipped...>

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Sorry about your injury. get ready, here it comes...
That sucks!
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For every complicated, difficult problem, there is a simple, easy
solution that does not work.
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Dave Jackson wrote:

Maybe raise the guard a bit for lighter materials to reduce the suction? Or use hold-downs?
Chris
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