More accurately or more probably, my poor adjustment of an Excalibur guard resulted in kickback today, resulting in 10 stitches to the back of my left thumb. I’ll describe the set-up, the results, post pics of the setup and the two pieces of material being cut and wait for responses re: what I did wrong and how can this be prevented in the future.
The task: cut 5 pieces of 1/8” Dibond (a signmaker’s sheet material – solid plastic core with aluminum faces front and back) down from 12” x 13” - 15” to 12” x 12”. In other words, cut 1 to 3 inches off one end. Single cut, each piece.
Before I turned on the machine, the plastic guard housing was offset left, close to the blade. I centered it (approximately) over the blade. With the fence set at 12”, I began cutting. On the second cut, the 1 1/2 x 12 offcut kicked back and caught my left hand square on the back of my thumb. The workpiece, that between the fence and blade, never moved. The kickback must have occurred after I had cleared the blade with the workpiece, for in the aftermath, there it sat, tight to the fence and several inches past the blade. The offcut sat on the front of the table, where it dropped after hitting my hand. Tomorrow’s pics will make it clear why it kicked back. What is still conjecture at this point is why it got into position to kick back.
I believe that the offcut was riding just inside the left edge of the plastic guard housing, and a small lateral shift of the housing that occurred when the workpiece cleared the blade and guard forced the offcut into the path of the back of the blade. If so, then the gross error was in not making sure that the left edge of the guard housing was on top of the offcut, an adjustment that would need to be checked before each cut. I will confirm this, if true, when I reconstruct the incident tomorrow.
Other considerations:
1.There is no splitter installed. I’m not sure that one would have helped. Perhaps. I’ll take the heat if you all disagree.
2.A sled would probably have been a wiser option, but I have become enamored with the overhead dust/chip collection of the Excalibur, and my sleds don’t allow use of same. Poor excuse, in retrospect. This may have been the gross error.
3.The overhead suction may have contributed to movement of the offcut, but I doubt it. I have seen it move veneer-thin strips and small chunks or knots,
4.The blade was left too high. Again, I doubt this was a major factor.
5.The cuts could also have been made on the SCMS.
I offer all this to warn any similarly ignorant Excalibur users as to the possible danger with this type of cut and to gain feedback so as to prevent it from ever happening again. I am quite aware of kickback causality between fence and blade, and always take care to prevent it. This is the first time I’ve experienced kickback from the left of the blade.
As an aside, I was not positioned to the left of my workpiece, as is generally recommended. Had I been so, I believe I would have suffered torsal or head trauma – Dibond edges are sharp! As it is, I nearly severed the extensor tendon in the thumb, the one that allows the thumb to straighten. I’m in a splint for 2 – 3 weeks while the tendon (presumably) heals.
So fire away folks, and Excalibur users be warned. Pics, and perhaps further enlightenment tomorrow.
Bruce
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But I haven't ever had a piece kick from rubbing the side of the blade....I would think it pretty hard to build up any serious momentum from that spot??? Mind you we're talking about the off-cut side where there's not much pressure even if the guard were moving around a bit. Fence side is obviously a different story.
