Rule 20 of 31 · Chapter IV — Keep Tools Sharp

Unplug tools before changing blades

Why this rule exists

A power tool that starts while your fingers are on the blade doesn't give second chances. Bumped triggers, faulty switches, a helper flipping the wrong breaker, it only takes one surprise to turn a routine blade change into an emergency. Pulling the plug removes all doubt: no electricity, no accidental start, full stop. It takes three seconds and it's the difference between a boring swap and the worst kind of shop story you never want to tell.

In practice

Physically unplug the tool, or lock out the switch, before you touch a blade, bit, or cutter, table saw, router, circular saw, all of them, no exceptions. Don't trust the power switch by itself to keep you safe. Keep the pulled plug in plain sight while you work so you can see it's actually out. On battery tools, pull the pack right out. Make it a hard ritual: hands never go near the cutting edges until the tool genuinely cannot start.

When it doesn't apply

There isn't a good reason to skip this one. The only nuance is method: cordless tools get the battery removed instead of a cord pulled, and hardwired machines get their disconnect or breaker locked out. The principle holds without exception, cut the power before you touch the cutter.