A thickness planer has a pretty straightforward job: Feed a board through one end and it comes out the other side smoother, flatter, and thinner.
But that's only part of what this machine can do.
With a few simple jigs and techniques, you can use a planer to solve several common stock-preparation problems. It can help flatten bowed or twisted lumber, straighten an edge, thickness thin stock, and produce a group of matching parts.
Here are five ways to put your planer to work beyond basic thicknessing.
1. Flatten Warped Boards with a Planer Sled
A thickness planer normally can't flatten a warped, bowed, or twisted board on its own.
That's because the feed rollers press the board against the planer bed as it passes beneath the cutterhead. If the board is bowed or twisted, the rollers can temporarily flatten it during the cut. Once it exits the planer, the board can spring back toward its original shape.
The solution is to give the board a stable reference surface with a planer sled.
Place the workpiece on a long, flat sled and check for gaps beneath it. Slip shims into the gaps until the board is fully supported and no longer rocks.
The goal isn't to force the board flat. The shims simply support it in its natural position so the feed rollers can't distort it as it passes through the planer.
A few small dabs of hot-melt glue can keep the shims from moving.
Start with a Light Pass
Find the highest point on the upper face and adjust the planer for a very light initial cut. A shallow "skip" pass — removing no more than about 1⁄32" — lets the knives begin removing the high spots without taking off unnecessary material.
Continue making shallow passes until the entire upper face has been surfaced.
At that point, you've created the flat reference face the planer normally requires. Remove the board from the sled, turn it over, and plane the opposite face normally.
WOODSMITH TIP: Don't Press a Warped Board Flat. The sled and shims should support the workpiece, not force it into a different shape. If you press a bowed board flat before securing the shims, you'll simply reproduce the bow when the board is released.
2. Straighten an Edge with Your Planer
A planer can also help straighten and square the edge of a board. The challenge is keeping the workpiece stable while it's standing on edge.
A pair of simple outriggers solves the problem.
Attach two narrow, straight boards to the face of the workpiece with double-sided tape. Position the outriggers so their lower edges are flush with the edge you're using as the reference surface.
The wider footprint keeps the workpiece upright as it travels through the machine, much like a jointer fence keeps a board square to the cutterhead.
Set the planer for a light cut and pass the assembly through until the exposed edge is straight and smooth.
This can be especially handy when you don't have a jointer available or you're working with a board that's awkward to handle on one.
WOODSMITH TIP: Start with Straight Outriggers. The accuracy of this setup depends on the auxiliary pieces. Make sure they're straight and securely attached before sending the assembly through the planer.
RELATED ARTICLE: How to Get More From a Thickness Planer: 2 Useful Planer Jigs
3. Plane Thin Stock with an Auxiliary Bed
Every planer has a limit to how thin a workpiece can be before the cutterhead and feed system can no longer handle it properly.
But there are plenty of woodworking projects that call for stock thinner than that limit.
Instead of trying to lower the cutterhead farther, raise the workpiece.
A simple auxiliary bed can be made from a flat piece of plywood sized to fit the planer bed. Covering the upper face with plastic laminate creates a smooth, low-friction surface.
Cleats underneath the auxiliary bed hook over the outside edges of the infeed and outfeed tables to keep the bed from sliding as stock is fed through the machine.
The added thickness effectively raises the planer bed, allowing the feed rollers and knives to engage thinner workpieces.
Feed the stock with the grain and use very shallow cuts until you reach the desired thickness.
WOODSMITH TIP: Check Your Planer's Limits. Before planing thin stock, check the manufacturer's instructions for minimum stock thickness and other operating requirements. An auxiliary bed changes the effective bed height, but it doesn't eliminate the need to follow the machine's operating guidelines.
4. Plane Matching Parts to Exactly the Same Width
When you're building doors, face frames, or other assemblies with multiple matching parts, small differences in width can create problems later.
Your planer provides a simple way to make a group of parts match.
Start by cutting all of the pieces to approximately the same width. Then stand the pieces together as a group and feed them through the planer at the same time.
Because all the parts pass beneath the cutterhead together, their edges are planed to the same dimension.
This is particularly useful for parts such as:
- Door rails and stiles
- Face-frame components
- Table aprons
- Drawer parts
- Other sets of matching components
Take light passes and continue until the entire group reaches the desired width.
The real advantage isn't simply hitting a particular dimension. It's consistency. Even if the finished parts end up a few thousandths above or below your target, they'll all match one another.
5. Support Short Workpieces
Short boards present another challenge at the planer. The feed rollers need enough workpiece length to maintain control as the stock moves beneath the cutterhead.
If a part is shorter than the minimum length specified for your planer, don't simply feed it through by itself.
One approach is to temporarily make the workpiece behave like a longer board.
Attach longer, narrow scraps along the sides of the workpiece with double-sided tape. The auxiliary pieces extend beyond both ends of the workpiece and span the feed rollers as the assembly travels through the machine.
The support strips should be at least as thick as the workpiece and installed with their bottom edges flush with its bottom face.
This gives the planer a longer assembly for its feed system to control.
WOODSMITH TIP: Manufacturer Guidelines Come First. Minimum stock length varies by planer. Check the owner's manual before using any technique involving short stock. If a setup doesn't meet the manufacturer's operating requirements, use another method to thickness the part.
Turn Your Planer Into a More Versatile Shop Tool
A thickness planer is still at its best when it's doing what it was designed to do — creating smooth, parallel faces. But understanding how the machine works makes it possible to tackle a much wider range of stock-preparation jobs.
The common thread behind all five techniques is support and reference. A sled gives warped lumber a stable reference surface. Outriggers keep an edge square. An auxiliary bed supports thin material. Gang planing keeps matching parts consistent. And longer support pieces provide better control for short workpieces.
A few simple shop-made accessories can turn a seemingly single-purpose machine into one of the more versatile stock-preparation tools in your shop.
Flatten Warped Boards & Plane Thin Stock with One Jig
Want a more permanent solution for two of the most common planer challenges? Our Double-Duty Planer Sled combines a sturdy torsion-box base with five adjustable, non-slip levelers to support bowed, warped, or twisted boards up to 48" long.
Remove the levelers and the same sled can serve as an auxiliary bed for planing thin stock. It's a simple shop-built upgrade that adds a lot more capability to your thickness planer.
GET THE STEP-BY-STEP WOODWORKING PLANS → Build a Double-Duty Planer Sled
