What Does a Jointer Do?

The jointer is considered one of the three essential stock-dressing machines in woodworking, along with the table saw and planer. But what exactly does a jointer do and how does it work? And when do professional woodworkers need to use one?

What is a jointer?

A jointer is a woodworking machine used to flatten, smooth, and square the edges of a lumber board. It corrects material defects, like warping or cupping, and in cabinetry or furniture projects, prepares board edges for gluing and fastening.

Most woodworking operations can be performed mechanically or manually. A jointer is the mechanical version of a hand tool called a jointer plane.

How does it work?

A jointer has four main components; an infeed table, an outfeed table, a fence, and a cutter head.

The infeed table and outfeed table sit coplanar, meaning they’re on the same plane and perfectly flat. The infeed table supports the board as it approaches the cutter head; the outfeed table supports the milled portion of the board.

The height of the infeed table is set according to the thickness of the layer being removed from the board; the surface of the outfeed table is fixed and flush with the height of the cutter head. The jointer fence runs perpendicularly along the edge of both tables.

Lowering the infeed table with the handle adjusts the depth of cut, or amount of material removed. The board is fed along the fence and across the cutter head, creating a flat surface. Several passes may be necessary to remove material defects or flatten a board.

The average depth of cut for most projects is around 1/16 to 1/8 inch, which explains why jointers come in various sizes. A 6-inch jointer is the most common, meaning the cutter head is 6 inches long, making this the maximum board width the machine can handle. The length of the infeed and outfeed tables, known as the bed, also varies; the longer the bed, the larger the reference area, and the longer the boards the jointer can process. As a general rule, a jointer can handle boards up to twice the length of its bed.

What can you do with a jointer?

You can take on several projects with a jointer, such as flattening defective boards or squaring stock.

Do you need a jointer for your woodworking project?

Your need for a jointer depends on your type of work. If you buy dressed lumber, or if you’re just getting into woodworking, you probably don’t need a jointer at this point. On the other hand, if you want to save money by purchasing rough lumber, or if your cabinets or furniture projects call for precise dimensions and angles or advanced joinery, a jointer can help make your milling process easier and more accurate.

That being said, a jointer usually isn’t the first piece of machinery you should get for your shop, especially if you can only afford one or two pieces of equipment to start. A table saw or a planer might be a better option.

A jointer is the power tool equivalent of a jointer planer, a type of hand plane. You can always prep and bring lumber to dimension with hand tools, but this approach might be less accurate, and may be more time-intensive and demanding than you’d like.

Choosing between a jointer and planer

Jointers and planers are different, but often used in unison. Most woodworkers would agree you need a jointer and planer to get the most out of your rough lumber. There are also jointer-planer combos on the market.

A jointer can flatten and square a board, but it can’t mill a board to a consistent thickness, nor is it useful for milling a board to precise dimensions. While you can use a jointer to flatten both faces or all four sides of a piece, this usually results in a tapered board, or a board that’s thicker on one end than the other. A jointer can produce flat edges, but it’s not designed to keep opposing sides parallel to each other.

A planer, i.e. a thickness planer, is a thicknesser: It trims a board to a consistent thickness throughout its length, rendering it perfectly flat on both surfaces. Before going into a planer, a board should have one flat side with a square edge—which is where the jointer comes in. Once jointed, the board is then fed through the planer, its flat side against the planer bed. The planer then cuts the rough top side of the board, making the second face parallel to the first.

Using a jointer

Safety tips 

A jointer must be precisely tuned to work properly and safely. Every machine is different, so get to know your jointer’s settings and features before using it. 

Tips for better results

As with any piece of woodworking equipment, proper technique comes with practice. Here are a few pointers to set you off on the right foot:

As you cross from the infeed table to the outfeed table, maintain consistent pressure across the length of the board without overreaching. Don’t move pressure from one side to the other, and don’t adjust your pressure with the board’s dips and humps. Keep an eye on the space between the board and the table, as well as the board and the fence.

MT Copeland offers video-based online classes that give you a foundation in construction fundamentals with real-world applications, like how to build a freestanding deck. Classes include professionally produced videos taught by practicing craftspeople, and supplementary downloads like quizzes, blueprints, and other materials to help you master the skills.

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