What's inside
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What does a planer do? A wood planer removes a controlled amount of material from the top face of a board so the board reaches a more uniform thickness and a smoother, more parallel face.
In a typical workshop, “planer” means a thickness planer, also called a surface planer or thicknesser. It is different from a jointer: a jointer flattens one reference face and squares one edge, while a thickness planer makes the opposite face parallel to that reference face. Used together, the two machines turn rough-sawn timber into accurately sized stock.
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What a planer machine does to a board
Imagine a rough board that is approximately 25 mm thick, but varies between 22 and 28 mm, with saw marks across its surface. A thickness planer feeds the board beneath a rotating cutter head. Infeed and outfeed rollers hold the timber down while knives remove a thin layer from the upper face.
After several passes, the board might be reduced to a consistent 20 mm. The newly cut face will be smooth enough for many projects, and its thickness will be much more uniform. The planer does not simply “sand” the wood: it cuts material with knives, so it removes stock quickly and establishes a dimension.
- Uniform thickness: it brings boards to a repeatable measurement.
- A smoother face: sharp knives remove much of the rough-sawn texture.
- Parallel faces: when one face starts reasonably flat, the new face follows it.
- Repeatability: multiple boards can be processed to the same setting.
That is the practical answer to “what does a planer tool do?” It sizes and smooths a board’s upper face relative to the face resting on the planer bed.
Thicknessing versus jointing
| Task | Machine or method | What it establishes | What it cannot reliably do alone |
|---|---|---|---|
| Flatten one face | Jointer, hand plane, or flattening sled | A flat reference face | Consistent thickness across the board |
| Square one edge | Jointer or table saw with a straight reference | An edge at 90 degrees to the face | Flatten a badly twisted board |
| Make the opposite face parallel | Thickness planer | Uniform thickness and a smoother upper face | Remove severe bow or twist safely without support |
| Improve final surface quality | Sander, scraper, or hand plane | Finer finish and removal of minor cutter marks | Correct major dimensional errors efficiently |
A jointer cuts from a fixed table and can create a flat first face. A thickness planer references the board from below, so it follows the shape presented to it. This distinction explains why a planer can make a bowed board thinner without making it flat: the board may simply flex as it passes through, then spring back after leaving the machine.
Step-by-step: taking a rough board to finished thickness
1. Inspect and prepare the stock
Check for nails, screws, stones, loose knots, and dirt. Remove metal before it reaches the knives. Mark the grain direction and circle defects. Measure the board at several points with calipers or a reliable rule, then choose a finished thickness that leaves enough material for flattening and cleanup.
For example, if a board varies from 22 to 28 mm and has a moderate cup, planning directly to 20 mm may leave thin areas or fail to remove the distortion. A safer target may be 18 or 19 mm after flattening, depending on the project.
2. Establish a flat reference face
Use a jointer, a well-tuned hand plane, or a flattening sled on a suitable router setup. Remove high spots gradually until the board rests without rocking. Mark the completed face with a pencil. This is the face that will sit on the planer bed.
If the board has a serious bow, twist, or cup, do not expect the thickness planer to correct it by itself. A sled supports the board in a stable position while the first face is cut. Wedges or hot-melt glue can hold the timber in place; remove the supports before processing the opposite face in the normal way.
3. Set the planer above the current thickness
Set the cutter head for a light cut, often about 0.5 to 1.5 mm on a straight-grained hardwood. Take less on wide, figured, brittle, or difficult stock. The ideal depth depends on machine power, board width, species, knife condition, and the manufacturer’s instructions.
4. Feed the board with the reference face down
Keep the board flat on the bed and support long stock at the infeed and outfeed sides. Do not force it into the rollers or pull it through while the cutter head is engaged. Keep hands clear of the cutter opening and follow the machine’s guarding and dust-collection requirements.
5. Take successive light passes
After each pass, measure the board at both ends and in the middle. Reduce the setting in small increments rather than trying to remove the entire difference at once. Stop when the full face has been cleaned and the board is slightly above its final dimension.
As a worked example, suppose the board is 24.0 mm after flattening and the target is 20.0 mm. Four passes removing 1.0 mm each may be reasonable on a capable machine, but a difficult hardwood might require eight passes at 0.5 mm. The cutting distance is the same, but the lighter approach reduces strain, tear-out, and the chance of stalling.
6. Make a finishing pass and check the result
Take a shallow final cut, then measure thickness across the board. A planer is doing its job when the readings are consistent within the tolerance your project requires. Light cutter lines can often be removed with sanding or a finishing plane.
What a planer cannot fix
A thickness planer cannot reliably flatten a board that rocks, twists, or has a pronounced bow when placed on the bed. It also cannot make a crooked edge square, remove deep end checks without shortening the board, or guarantee a perfect finish on reversing grain.
It may reduce a mild cup after one face has been flattened, but that is not the same as correcting the defect. For badly distorted stock, flatten the first face with a jointer, hand plane, or sled. Then plane the second face parallel. If you skip the reference-face step, the finished board can be consistently thin while still carrying unwanted distortion.
Typical planer specifications that matter
| Specification | Common benchtop range | Why it matters |
|---|---|---|
| Maximum width | 305–330 mm | Determines the widest board the machine can accept. |
| Maximum stock thickness | 150–180 mm | Sets the upper limit for beams and thick slabs. |
| Minimum stock thickness | 3–6 mm | Important when making thin panels or strips; check the manual. |
| Typical cut depth | Up to about 2–3 mm per pass | The maximum is usually for narrower, softer stock, not a recommended everyday setting. |
| Motor input | 1,500–2,200 W corded | More capacity can help with wide hardwood, but knife sharpness and feed rate also matter. |
| Approximate machine weight | 25–40 kg | Heavier machines tend to be easier to keep stable and may produce less vibration. |
| Dust port | 63–100 mm | A compatible extractor helps visibility, chip evacuation, and cleanup. |
These are representative categories rather than guarantees for every model. Before buying, compare the actual maximum width, minimum thickness, cutter-head design, knife availability, noise level, table extension quality, and the space needed for infeed and outfeed. A machine that weighs 30 kg may fit on a bench, but a 2-metre board still needs several metres of clear handling space.
Choosing a planer by situation
| Your situation | Sensible choice | Reason |
|---|---|---|
| Occasional DIY work and limited budget | Compact benchtop thickness planer | Lower purchase cost and storage footprint; accept more noise and setup time. |
| Regular furniture making | Sturdier 305–330 mm benchtop model or stationary planer | Better support, repeatability, and durability for repeated stock preparation. |
| Mostly rough, twisted reclaimed timber | Planer plus a flattening method | The planer alone cannot create the first flat reference face. |
| Small workshop with infrequent use | Portable machine with folding tables and accessible replacement knives | Easier to store; consumable availability matters more than peak capacity. |
| Large volumes of hardwood | Heavier stationary machine with stronger dust extraction | Improves stability and reduces interruptions, but requires more space and budget. |
As a broad 2026 market guide, compact benchtop machines commonly occupy the lower-to-middle hundreds in local currency equivalents, while heavier stationary equipment can cost several times more. Include the cost of knives, sharpening or replacement cutter inserts, dust extraction, a mobile stand, and electrical upgrades where relevant.
Ownership realities: knives, snipe, and maintenance
The parts that usually need attention first are the knives or cutter inserts, feed rollers, drive belts, and table surfaces. Dull knives increase noise, tear-out, motor load, and the temptation to take overly deep cuts. Keep spare knives available and replace or rotate them according to the design. Disposable double-edged knives are convenient; resharpenable knives can be economical if you already have suitable sharpening equipment.
- Vacuum chips from the bed, rollers, and cutter-head area after use.
- Keep the tables clean and apply only a manufacturer-approved low-friction treatment.
- Inspect rollers and belts for resin buildup, slipping, or uneven feeding.
- Support long boards to reduce snipe, the shallow dip often cut at the leading or trailing end.
- Do not plane wet, dirty, painted, or metal-contaminated timber.
- Use hearing protection, eye protection, and effective dust extraction.
Common mistakes include feeding a bowed board without a sled, taking the maximum advertised cut on every pass, ignoring grain direction, and measuring only one location. A planer is most useful when treated as a precision sizing machine—not as a substitute for every flattening and jointing operation.
Bottom line
What does a surface planer do? It cuts the upper face of a board to a controlled height, producing smoother, more uniform, and generally parallel stock. It is excellent for thicknessing rough timber after one face has been flattened. It cannot, by itself, correct significant bow or twist; that requires a jointer, hand plane, or flattening sled first.