Jointer vs Planer for Flattening Reclaimed Timber
What's inside
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Reclaimed timber can look flat and still rock on a workbench. Old boards may be cupped, twisted, bowed, or covered with nails and grit. A jointer and a planer do different jobs: the jointer creates one flat face and a square edge; the planer makes the opposite face parallel to that reference face. Neither machine, used alone, reliably flattens a badly twisted board from both sides.
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Contents
What each machine does
A jointer cuts the underside of a board against its table. Its infeed table is lower than the outfeed table by the depth of cut, and the cutterhead shaves high spots as you feed the wood. With a sound technique, repeated passes establish a flat face. The fence can then help make one edge square to that face.
A thickness planer feeds a board over a cutterhead and removes material from its top face. It is good at making boards a consistent thickness, but it does not correct twist by itself. If a twisted board enters the planer, rollers press it down temporarily. It springs back after the cut, still twisted but thinner.
For a board with a genuinely flat reference face, the planer is usually the faster way to bring the opposite face parallel. For a single face that must be flattened, the jointer—or a sled in the planer—is the relevant tool.
Quick comparison
| Task | Jointer | Planer |
|---|---|---|
| Flatten one face | Yes, within machine width and cut capacity | Not reliably without a flattening sled |
| Make opposite face parallel | Not its main job | Yes, once one face is flat |
| Square an edge | Yes, with a properly set fence | No |
| Typical limitation | Board wider than the cutterhead or too short to control safely | Twist or bow remains when rollers release the board |
| Useful reclaimed-wood concern | Hidden metal can damage knives | Metal can damage knives and create a serious hazard |
Check the wood before switching on
Metal is the first failure mode to prevent. A nail or screw can chip knives, damage carbide inserts, or be thrown from the machine. Look over every surface and edge, use a detector suited to locating metal in wood, and remove fasteners completely. A detector is not a guarantee: old timber can contain broken nail tips or fragments embedded below the surface. If you cannot establish that the board is clear, do not put it through a jointer or planer.
Remove loose dirt and grit with a stiff brush. Sand or scrape off surface contamination that could dull cutters. Check for loose knots, splits, and rot; a cutter can lift a loose knot and turn it into a projectile. Also let the timber acclimate to the shop. Wet wood can cut poorly and may move as it dries. A moisture meter is useful when the finished piece needs stable dimensions; for indoor furniture, wood around 6–9% moisture content is common, though local conditions matter.
Jointer, then planer: the usual workflow
For boards narrower than the jointer’s cutterhead, joint the best face first. Take light cuts—often about 1/32 inch (0.8 mm) or less on rough, unpredictable stock—and inspect the board between passes. Press down over the infeed table at the start; once most of the board is on the outfeed table, shift pressure there. Holding the board down hard across its full length can make the machine follow a bow instead of removing it.
When the face no longer rocks against a straightedge, mark it as the reference face. Run that face down in the planer, taking modest cuts until the opposite face is parallel and the board reaches the needed thickness. Then joint an edge square to the reference face if the project requires it. A board that is badly twisted may need to lose substantial thickness before it cleans up; check the likely finished dimensions before cutting away good material.
Do not try to flatten a very short or narrow piece if it cannot be held and fed securely. Follow the machine manual’s minimum workpiece dimensions and use push blocks where specified. Reclaimed boards also vary in grain direction, so tear-out may occur even with sharp knives and shallow cuts. Reversing the feed direction is not a safe fix on machines that are not designed for it.
If you own only a planer
A planer sled can let a planer flatten one face without a jointer. Support the board on a rigid, flat sled, shim beneath the low spots so the board cannot rock, and secure it so it cannot shift. The planer removes high spots while the board stays fixed in that position. Once the first face is flat, remove the board from the sled and plane the other face parallel.
This method is slower than jointing and uses extra height in the machine, so check the planer’s capacity. Thin shims or wedges must be secured; a loose piece can be pulled into the cutterhead. A sled also does not make metal detection or stable board support optional. For occasional flattening, this can be a sensible reason to buy a benchtop thickness planer instead of buying two machines.
Which machine should you buy?
Choose a jointer first if your main problem is twist and cup on boards narrower than its capacity, or if you need to prepare square edges for glue-ups. A 6-inch jointer handles many furniture parts, but it cannot flatten a board wider than 6 inches in one pass. A wider jointer costs more and takes more floor space; for wide slabs, a router sled or local milling service may be more practical.
Choose a planer first if your stock already has one reasonably flat face, you need repeatable thickness, or you plan to flatten occasional boards with a sled. For a budget-conscious shop, a planer plus sled can be enough. Buying a planer and assuming it will flatten twisted lumber unaided is the more expensive mistake.
If reclaimed timber is the main material, prioritize capacity, cutter condition, dust collection, and safe support over extra features. A benchtop jointer can establish faces on manageable parts, but short beds make long boards harder to control. A planer flattening sled is a lower-cost workaround for occasional wide stock, not a substitute for checking the board’s support and stability.
Make the choice around your boards
Measure the widest and longest pieces you actually expect to use, then check the machines’ stated capacities and minimum workpiece sizes. If most boards are narrow and twisted, a jointer solves the reference-face problem directly. If they are already flat on one side, a planer does more useful work per pass. If boards are wider than either machine can safely handle, consider a sled or outside milling rather than forcing the stock through.
