The planer: the machine that feeds itself
The thickness planer is the only machine in the shop that takes the board out of your hands on purpose. That's its safety contract: the rollers do the feeding, and your hands never need to be anywhere near the cut. Every planer injury starts with someone amending that contract.
Machines and tools vary by brand, model, and age. Your manual outranks this page — read it first.
Inside the case, a cutterhead spins between two powered rollers: the infeed roller grips the board and pulls it through, the outfeed roller sends it out the far side. You start the board; the machine finishes it. Understand that hand-off and the rules write themselves.
Hands stop at the lip
Once the infeed roller has the board, your job is over. Fingers that follow the board past the infeed table's edge are entering the machine behind a roller specifically built to grip and pull — and the roller that pulls a 12-foot plank through will pull a hand in just as readily.
Length, thickness, and the sled
A board must be long enough to span both rollers at once — most manuals put the minimum around 12″, and yours has the real number. Shorter stock reaches a moment where neither roller holds it, and a cutterhead spinning at full speed over an ungripped block turns it into a projectile. The same manual sets a minimum thickness; below it, carry thin stock through on a sled (a flat board beneath it) rather than asking the rollers to grip a wafer.
Reclaimed wood earns its reputation
Old lumber hides old hardware: sheared nails, staples, fence wire grown into the grain. A planer knife meeting a hidden nail chips the knife and can fire steel fragments out of the openings — and it happens most with exactly the salvaged material a planer is most tempting for.
Beyond that, the planer mostly asks for the shop-wide basics: hearing protection every session — planers sit at the loud end of the noise chart — dust collection connected, because a planer without it fills a room in minutes (the dust article explains why that matters), and chips cleared only after spin-down, with the plug out if your hands go anywhere near an opening.
Keep the contract — you start the board, the machine finishes it, hands outside, body out of the ejection line — and the planer is honestly one of the safest machines you own. It was built to run without you close by.