Intel's Ronler Acres Plant

Silicon Forest

Thursday, July 3, 2014

Kickback


For as long as I can remember I have 'known' about the dangers of kickback from power saws, but until recently I had never encountered it. Obviously power saws can be very dangerous. That sharp steel blade spinning at nine zillion RPM would make mince meat of any part of your body it came in contact with, so you need to careful when operating these things.
    Once upon a time I was working with a crew of wild men framing apartment buildings in Houston. These guys were an OHSA inspector's worst nightmare, or would have been if OHSA knew about them. These guys didn't believe in safety guards. We used pneumatic nail guns that had a safety latch that kept them from firing unless they were pressed hard up against something. These guys had wired the safety's back because it took too long push down on the nail gun to disengage the safety, or they were just philosophically opposed to any kind of safety contrivance, I'm not sure which it was. 
    They had also removed the guards on their circular saws. I can sort of understand that, those things can make it a little difficult to get saw the started on cutting. Most people accept that little bit of extra effort as a worthwhile trade off for keeping the blade covered when it is not actually in use. Removing the guard also meant you had to turn the saw upside down before you set it down, otherwise the blade would be cutting into the floor. These guys seemed to think it was a worthwhile trade off. I thought they were nuts, but hey, I needed a job, and it just meant I had to stay on my toes.
    Evidently I wasn't quite up to par because I had a couple of minor accidents while I was working with these guys. Late in the day and I'm tired. I'm standing there holding a nail gun and I've forgotten about the safety being wired up and I let a little too much weight rest on my trigger finger and bang! I shoot myself in the leg. It went in my calf muscle at an angle, and not too far. Didn't hurt much, and when I pulled the nail out it didn't bleed much. More embarrassing than anything. Still have a spot on my leg that acts up from time to time, but it's never given me any serious trouble.
    Another time we were putting up a wall. I was standing inside on the floor and another guy was standing outside on the ground, a couple feet below floor level. He wants to set his saw down so he reaches in between two studs so he can set in on the floor. At the same time I take a step in his direction. My leg and the saw arrive at the same place at the same time. Fortunately, the blade only caught my pants leg, but that was enough to get everyone's attention. It was also a bit of a financial disaster. Blue jeans cost money, and wages were weak, somewhere around $5 an hour.
    Both of these incidents occurred within a month of each other. I think the reason these guys didn't have more accidents is because they were used to working with each other and they were all familiar with each other's patterns of motion. I was the new guy and I didn't fit very well, especially since I thought they were crazy, and maybe not too bright, but hey, Gulf Coast of Texas, in the summertime, what can you expect?
    So anyway, I've used power saws and I've had problems with them, but I've never had a serious kickback incident. One reason might be because most of my work has been with hand-held circular saws (Skil saws). These things weigh somewhere around five or ten pounds, and they require a bit of force to push them through the wood, even when they are sharp, so any 'kickback' that occurs has to overcome the inertia of the saw and the force of your arm.
    If you are cutting a poorly supported board, the board can bend and the sides of the cut can bind on the saw blade, but this usually results in slowing the saw down or even stopping it, and it's immediately obvious that you need to release the trigger because you are not cutting anymore.
    
    A young man I know recently lost a couple of fingers from his off hand (the left hand, he's right handed) in an accident with a table saw. When I first heard about this I assumed his hand had come in contact with the blade, but that was not the case. He was cutting a groove in a piece of hardwood, something went wrong, the saw blade grabbed the piece of wood and threw it back at him, striking the little and ring fingers of his left hand and severing them. This is the first and only injury due to kickback that I have heard about.

Be careful with power tools.

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