A wood jointer flattens one face and squares one edge of a board using a rotating cutterhead between an adjustable infeed table and a fixed outfeed table — but it never makes the opposite face parallel.
Run a cupped board across a jointer and you get one dead-flat reference surface. That’s the whole job. The opposite face stays rough and unparallel, which is why a planer follows the jointer in almost every real workflow. Confusing the two machines wastes money and produces tapered boards, so it’s worth knowing exactly which one does what before you buy.
The Two Tables That Control Everything
Cut depth is set entirely by the height difference between the infeed and outfeed tables, and the outfeed table must sit flush with the cutterhead’s cutting circle or every board will come out tapered.
The infeed table is the one you adjust. Lowering it below the outfeed table increases how much material the knives remove; raising it reduces the cut. The outfeed table supports the freshly cut surface as it leaves the cutterhead and normally stays fixed.
The cutterhead sits between the two tables, fitted with either straight knives or helical/spiral insert cutters. Helical heads use small replaceable carbide inserts arranged in a spiral, which cuts quieter and lets you rotate a damaged insert instead of replacing a whole knife set. The fence holds the board at a controlled angle — usually 90 degrees for a square edge, though many machines bevel from 0 to 45 degrees.
One piece of hardware is non-negotiable: the guard covers the exposed cutterhead everywhere except where the workpiece passes. Never defeat it.
How Does a Jointer Actually Flatten a Board?
A jointer removes the high spots and nothing else, because the board rides on the flat tables rather than being forced against a fixed thickness stop. That distinction is why the machine can straighten a twisted board but cannot thickness it.
Here’s the documented sequence, drawn from Harvard’s Graduate School of Design shop procedure and a published jointer standard operating procedure:
- Inspect the stock for knots, warping, and embedded metal. Remove jewelry, secure loose clothing, confine long hair, and wear eye and hearing protection.
- Set the fence, cut depth, and tables with the power disconnected.
- Confirm the guard works, the fence is locked, the tables are tight, and the stock isn’t touching the cutterhead at startup.
- Start dust collection before the jointer — connect the hose and open the gate first.
- Place the concave or rough face down for face jointing, hold the board firmly against the fence and table, and feed steadily from the infeed side only.
- Use push sticks or safety blocks whenever fingers would come within 2 inches of the cutters.
- Switch off and wait for the cutterhead to stop completely before cleaning or adjusting anything.
Success looks like this: a single continuous shaving along the full length of the board, with no snipe at either end. Stop-and-start shavings mean you’re feeding unevenly or the outfeed table is out of alignment. New users should also read the machine-specific setup instructions — Harvard GSD’s jointer-planer procedure covers the guard, dust collection, and table-alignment requirements in detail.
Face Jointing Versus Edge Jointing
Face jointing flattens the wide surface of a board with the fence set at 90 degrees; edge jointing squares the narrow edge so glue joints close tight. Both use the same cutterhead and tables — only the board orientation changes.
In practice, the order matters. Flatten a face first, then reference that flat face against the fence to joint the edge square to it, then run the board through a planer to bring the opposite face parallel. Skipping the planer leaves you with one flat face and one rough one, and any project requiring consistent thickness will show it.
If you’re comparing machines for a home shop, this breakdown of tested wood jointing tools for home shops covers benchtop versus long-bed models and what each class actually handles.
Benchtop Versus Long-Bed: What the Numbers Look Like
Benchtop jointers handle shorter stock and cost a few hundred dollars; long-bed and helical-head floor models cost thousands and support longer boards through the cut. Prices below are retailer listings and shift with sales.
| Model | Key Specs | Listed Price |
|---|---|---|
| WEN JT630H | 6-inch spiral benchtop, 10-amp motor | $273.83 |
| WEN JT833H | 8-inch spiral benchtop, extendable table | $463.79 |
| Grizzly G0947 | 8-inch benchtop, 1.5 HP, 120 V, 11,000 RPM spiral head, 1/8-inch max depth, 16 HSS inserts | — |
| Jet 708466DXK | 6-inch long-bed helical head, 1 HP, 115/230 V | $1,899.00 |
| Jet JWJ-8HH-BLK | 8-inch helical head, 2 HP, 230 V | $2,699.00 |
| Powermatic 60HH | 2 HP, 230 V, single-phase | $2,999.00 |
The spec that matters most for home shops is bed length relative to the boards you actually buy. A benchtop model with a short bed struggles to flatten anything past about four feet because the board rocks as it exits. If most of your stock is dimensional lumber from a big-box store, a benchtop unit is fine. If you’re milling rough-sawn hardwood, the long bed earns its price.
Common Questions
Can a jointer replace a planer?
No. A jointer creates one flat face and one square edge but leaves the opposite face rough and unparallel. A planer is what brings the second face parallel and sets uniform thickness. Most shops need both machines, or a jointer plus a thickness planer, to turn rough stock into finished lumber.
What causes snipe at the end of a jointed board?
Snipe — a shallow dip at the board’s end — usually comes from the outfeed table sitting slightly below the cutterhead’s cutting circle, or from letting the board tip as it leaves the infeed table. Check the outfeed table alignment first, then keep steady downward pressure on the outfeed side as the trailing end passes the knives.
How much material should I take per pass?
Light passes produce cleaner surfaces and safer cuts. Grizzly lists 1/8 inch as the maximum cut depth on its 8-inch benchtop model, and that figure is a ceiling, not a target. On figured or hard stock, take half that or less and make additional passes until the face is clean.
Sources
- Harvard Graduate School of Design Fabrication Lab. “Standard Operating Procedure: Jointer-Planer.” Supports cutterhead, fence, guard, and dust-collection requirements.
- K–12 Newfoundland and Labrador. “Jointer Safe Operating Procedure.” Supports the step sequence, inspection, and push-stick guidance.