The Complete Handbook of Planers

Chapter 1: Understanding Planers

The planer you buy will define the quality and speed of your work more than almost any other tool in the shop, yet it is often the most misunderstood machine in the woodshop. To the uninitiated, a planer looks like a box with a hole in it. You feed a rough, uneven board into one side, a motor spins somewhere inside, and a perfectly dimensioned, flat piece of wood comes out the other side. The basic promise is that simple. The engineering and the craft required to make it work reliably, however, are not.

A planer—specifically a thickness planer, which is what this handbook primarily covers—is a machine that removes a controlled amount of material from the *thickness* of a board. It works by holding the board flat against a reference surface and passing it through a rotating cutterhead that shaves off a thin layer of wood from the top face. The result is a board with a consistent thickness along its entire length. This is distinct from a jointer, which flattens the *edge* of a board or flattens a face to create a true reference surface. A planer assumes you already have a reasonably flat face (usually from a jointer) and simply makes the opposite face parallel to it at a specific distance.

Why does this matter for your daily work? Consider the most common scenario in a professional cabinet shop. You receive a stack of 4/4 red oak, nominally one inch thick, from the