Jointer vs. Planer: What’s the Difference & Which One is Best for Your Needs?

Perhaps the most misunderstood power tools in the workshop are the planer and the jointer.

This could be, at least in part, because most of us buy pre-surfaced lumber at our local lumberyards. Nevertheless, these two tools are extremely useful, even if they are so poorly understood. They are not the same, as each has its own distinct purpose.

With S4S (sanded on four sides) lumber so prevalent today, it is possible to be an excellent woodworker without ever owning either of these tools.

However, those who buy rough cut lumber or who have their own sawmills just about have to have these to make their boards usable. Likewise, woodworkers who do delicate work, requiring lumber that is of unusual dimensions, especially thin wood, need these tools to be able to produce the boards they need to work with.

Much of the confusion about these tools comes from the similarity of their operation. Both have a rotary drum with blades, or knives, mounted on it, to machine the surface of the wood.

But that’s where the similarity ends.

It is the difference between these tools which is important. The knives (blades) of a jointer are mounted in the table, cutting from below, while the knives of a planer are mounted above the work-piece, cutting from above. It is impossible for a planer to do the work of a jointer and equally impossible for a jointer to do some of the work that a planer does.

Therefore, serious woodworkers will often have both of these tools in their shops, something that baffles others. Yet, in order to do the fine woodworking that they produce, these two tools are indispensable.

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What Does a Jointer Do?

A jointer has a flat bed, split at the cutter head. This allows the forward part of the bed to be raised and lowered, adjusting the amount of cut that is made on a pass. With the front bed lower than the rear, both ends of the boards being worked are supported at the same time, helping ensure an even cut and prevent damage to the board.

The jointer also has a fence, allowing boards to be held vertically on the bed, ensuring a perfectly perpendicular cut. This is of extreme importance when fulfilling the jointer’s primary purpose of preparing board edges for “jointing” or connecting together to make a wider board, such as for a tabletop.

Jointers serve another major purpose, especially when being used with rough-cut lumber, squaring up the board. In this operation, one side is selected as a reference side for the others to be squared up with. Starting with this side, all four sides of the board are passed through the cutter head, using the fence to ensure perpendicular sides.

This ability of the jointer does one more important thing for us; it gives us the ability to make warped, cupped or twisted boards flat and usable. This is, of course, easier with shorter boards, than longer ones, especially when dealing with twisted boards.

Nevertheless, the jointer is the only tool, other than a hand plane which can turn these less than optimum pieces of lumber into finished lumber, ready for use in fine woodworking projects.

What a Jointer Cannot Do

While jointers are very versatile tools, they still have limits. The prime one is that while you can set the thickness of cut, you can’t set the thickness of the finished piece. Therefore, it is virtually impossible to cut several boards to exactly the same thickness, unless they start out that way.

The jointer is also unable to ensure that opposite faces are parallel.

If you joint one edge and then flip the board over to joint the opposite edge, those two edges might not be parallel, unless your jointer is set up perfectly and the workpiece is held firmly against the fence.

This problem is magnified when jointing the surface of the face side, rather than the edge, as it is impossible to hold the board against the fence in such a way as to guarantee that the two faces end up parallel.

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What Does a Planer Do?

A planer consists of a flat bed for the board to ride on, with a cutting head mounted above the board. Input and output rollers control the speed of the material, as it passes through the cutting head. This provides for a smoother, more consistent finish than that which you can get from a jointer.

There are two specific purposes that planers are designed for, in addition to smoothing the face and back of a board. They are to ensure that the surfaces are exactly parallel and to shave off material to make the board a precise thickness. Several boards passed through a planer will come out the exact same thickness, regardless of what they were before, as long as the planer’s settings have not been changed.

These two tasks that a planer can accomplish are virtually impossible for a jointer to do effectively.

 While it is possible to thin boards to roughly the same thickness on a jointer, it is difficult to get them to the exact same thickness, as there is no control for thickness, merely for the amount being cut off.

Without the overhead rollers to ensure that the material is held flat to the bed and the overhead cutter being exactly parallel to the bed, it is impossible for a jointer to ensure that the opposite faces of the board are exactly parallel.

What a Planer Cannot Do

Using a planer as a jointer is basically impossible. Planers are not capable of doing much of what jointers do, specifically anything having to do with the edges of the board. Unless you are going to use very narrow boards, it is impossible to work the edges of the boards in a planer. Even if you do, there is no fence to hold them perpendicular to the bed or cutter head.

Since planers use pressure rollers to pull the material through, they cannot be used to remove cupping, warping or twists from the board. The pressure of the rollers will flatten the board against the bed, removing the deformation of the board long enough for it to be cut.

Once removed from the planer, the cupping or warping will still be there; the board will just be thinner.

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Jointer-Planer Combo

Purists would say there is no such thing as a jointer-planer, but they are wrong. Some people refer to a wide jointer as a jointer-planer, but they are equally wrong.

A true jointer-planer combines the features and operation of both a jointer and a planer, using the same cutting head for both. This gives you a very wide jointer, as well as the ability of making cuts of the exact thickness and exactly parallel, like you can with any other planer.

The secret to these power jointer and thickness planers is that there are two beds.

Looking at the machine, as it normally sits in a workshop, it looks like nothing more than a wide jointer. But when the jointer bed is lifted, you find another bed mounted below the cutter head, which is height-adjustable to control the thickness. The only other part of the switchover that is necessary is swinging the dust collector from its position for jointing, to its position for planning. In this position, it acts as a blade guard as well.

The advantage of a jointer-planer over separate units is that it takes up less space, effectively freeing up the space that would be required for the planer. On the flip side of the coin, you might end up with a smaller planer, if you buy an 8” joiner-planer, rather than a 12” one (most are 12.5”).

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Conclusion

It is clear that the difference between a jointer and a planer is significant. For those who are doing fine woodworking, it can make sense to buy both, especially if controlling wood thickness is an essential part of the design and build of projects.

For those who have limited shop space, the combination units are an ideal compromise, providing a lot of capability in a limited space. However, be careful to ensure that it is a true combination unit, with a planer bed below the cutter head. Some vendors mistakenly call jointers “jointer/planers” just because the jointer has a wide bed. But those are incapable of providing the accurate finish thickness of a planer.