My venerable hard drive has breathed its last. It was eight years old. I rely on the Internet for all my wages, and all I have is a low-end Dell from 2002 with the hard drive 99% percent full and XP patched to hell and gone, and now I don't even have that. So you get cut and paste from 2008, sent from my son's computer. Ashes, ashes, we all fall down.)
Let me tell you about safety.
If you live in the educated, white collar world, you know nothing of safety. That is to say: you know nothing of danger; you're insulated almost totally from real peril.
As you move up the intellectual food chain, and your experience with the world inhabited by those faced with real, daunting challenges is practically non-existent, your attenuated worldview becomes almost worthless to people who are faced with real danger.
If you are entirely insulated from the consequences of your actions, it would be decent to recuse yourself from offering advice to others, no less so than a man who stands to profit from the outcome. When a man is facing a spinning blade, the cardinal sin is to distract him. Yelling: "Look out!" is akin to shoving him into the blade. The time to identify danger is before, not after. It is predictability and stability and a certain kind of respect that is helpful. Nothing else.
Let me tell you about the blade. You think you can handle it because you fancy yourself intelligent. You're wrong. Because the danger it presents, the real danger, is hidden from you.
I watch people who have no business offering advice to anyone telling amateurs and professionals alike how to do what they're trying to do. I see the safety fetishist's clown shoes -- safety glasses worn to hang a picture -- and the matching squeak-nose of warnings over the toxicity of stuff you could eat, never mind touch, juxtaposed with behavior that reminds me of sheep sniffing around the shambles.
You think that you're smart. You think that you can put your hand near the blade, as long as you don't push your hand right in it. It doesn't work that way.
You have to avoid putting yourself in the position where your hand will be drawn into the blade and there's nothing you can do to stop it. There was no danger, really; you were maimed without danger announcing itself first. It was there all along in a way you'll never "get" until it's too late.
The wood lays there on the table. Perhaps it's some mundane species. Straight, plain grain. Maybe it's exotic or unusual. You like the look and feel of it. The smell of it. It gives you a little thrill to think what could be made from it. It's full of a kind of promise of a fantastic future.
But it grew from a little sapling. Buffeted by winds, warped and enfeebled by its greedy reaching to get up to the sun before the others that would wither in the shadow of its canopy, there are stresses built up in the wood. Maybe the tree grew straight up, but the ground where it was born and raised was tilted, and the constant stress was locked in the grain. Maybe the sawyer saw that it was growing at a crazy angle, and put it on the logging truck anyway, out in the landscape where no one would know that no straight timber could ever come out of it. He'd have his money and someone else closer to the blade would find out what was in there the hard way.
Besides the stresses in the wood, there is a phenomenon associated with how it is seasoned. Most wood must be seasoned out in the air -- or in an oven to do it quicker -- to allow it to become useful by acclimating it to its future use. Leaving the lumber out to dry is time consuming and has its risk: bugs and weather and fires and so forth. But there is a real danger in drying out the lumber too quickly in a kiln, too. It's referred to as case hardening. Sounds like metallurgy, but it's not. It means when you try to pass the blade through the baulk of wood, the tensions locked into the wood are released --or better put: are revealed-- by its travel through the blade. The outside of the wood seems OK. But the inside is different.
You are holding on to that piece of wood, if you trust yourself not to put your hand too near, and trust others never to fool you, or be fools themselves. You've been told that others have made you safe, and so you trust it a bit more than you should, maybe. On the table saw, the case hardened wood might pinch the saw kerf closed, and it will grab the back of the spinning blade and be hurled at you. Or conversely, perhaps you will hang on to it tightly enough, and it will buck and rocket away in some unexpected direction, and draw your hand into the abyss.