How to Adjust a Jointer Outfeed Table to Match Knife Height
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A jointer works properly only when the outfeed table supports the board immediately after the knives cut it. If the table is too low, the board drops as it leaves the cutterhead and the knives remove a second bite, creating a snipe-like dip at the trailing end. If it is too high, the board rides onto the table before the cut is complete, leaving a ridge or an uncut section.
The target is simple: with a knife at its highest point, the outfeed table should be level with the knife edge, or just a hair below it. On most machines, “just a hair” means roughly 0.001 to 0.002 inch below knife height. Accuracy matters more than a particular brand of measuring tool.
Contents
Before You Adjust Anything
Disconnect the jointer from power. Do not rely on the switch, and do not rotate the cutterhead with the motor connected. Remove the fence if it blocks access, then secure or remove the cutterhead guard according to the manufacturer’s instructions. Keep your fingers away from the knives even when the machine is unplugged.
This adjustment applies mainly to jointers with straight knives in a traditional cutterhead. Helical and segmented insert cutterheads still require the outfeed table to be correctly positioned, but the individual inserts are not normally adjusted to a common height in the same way. Check the manual before loosening anything.
Clean pitch and packed dust from the table tracks, elevation mechanism, and cutterhead area. A dirty track can make the table appear correctly adjusted at one end and wrong at the other. Also confirm that the infeed table is not being used as the reference. The outfeed table is set relative to the knife’s highest cutting arc.
Tools That Make the Job Easier
You can do this with a straightedge and a small ruler, but a few inexpensive tools make the result more repeatable. A 12- to 24-inch machinist’s straightedge is preferable to a framing square, whose edge may not be straight enough. A set of feeler gauges and a machinist straightedge is useful for measuring small gaps.
| Tool | Use | Trade-off |
|---|---|---|
| Steel straightedge | Bridges the outfeed table and cutterhead | Best general-purpose reference; must be genuinely straight |
| Feeler gauge | Measures a small gap under the straightedge | More precise than paper or a ruler |
| Dial indicator jig | Checks table height and variation across the width | Most precise, but slower to set up and unnecessary for occasional tuning |
| Small steel rule | Checks whether a knife moves a reference piece | Cheap and practical, but less quantitative |
A jointer knife setting jig can help if you also need to reset knives. It is not required for an outfeed-table adjustment, though. If your knives are already secure and cutting evenly, a straightedge and feeler gauge are usually enough.
Find the Knife’s Highest Point
Place a straightedge on the outfeed table so it extends over the cutterhead. Turn the cutterhead by hand in its normal cutting direction, using the pulley or a safe rotating point—not the knife edge. If the knife is below the table, the straightedge will not move. Raise the outfeed table gradually until the knife just touches the straightedge.
To confirm the high point, place a small, straight piece of wood about 2 to 3 inches long on the outfeed table with its end extending over the cutterhead. Rotate the cutterhead by hand. A correctly positioned knife will move the wood forward slightly—about 1/8 inch is a useful practical target—without lifting it or pulling it backward. Mark the cutterhead or pulley so you can return to this knife position.
Check the knife at the left, center, and right portions of its cutting edge. A knife that moves the test piece at one end but not the other may be incorrectly installed, unevenly ground, or sitting in a dirty pocket. Do not compensate for a twisted or badly set knife by tilting the outfeed table.
Adjust the Outfeed Table
Lower the outfeed table slightly, then place the straightedge across both the outfeed table and the cutterhead area. Rotate the cutterhead until a knife is at top dead center. Raise the table in small increments until the straightedge rests on the table and the knife just touches it.
For a production-quality setup, lower the table by approximately 0.001 inch. A feeler gauge should just enter the gap between the straightedge and table without forcing it. If you do not have a gauge, a single sheet of ordinary paper is roughly 0.003 inch thick and can indicate a small gap, but it is not a precision standard.
Tighten the table locking hardware gradually and recheck the height after each lock is secured. Many jointers shift slightly when the locks are tightened. Check at both sides of the table and near the center. If the gap changes across the width, inspect the table ways and locking mechanism rather than trying to split the difference.
Some jointers use handwheels, while others have fixed tables with adjustable knife height. If the table will not move smoothly, do not force the handwheel. Remove accumulated dust, lubricate only where the manual allows, and inspect for a loose gib or damaged elevation screw. A dry table lubricant for woodworking machinery can reduce sticking, but it will not correct a bent or worn mechanism.
Test the Setup With Scrap
Reconnect power and make a light cut on a straight, flat board. Use a shallow pass, around 1/32 inch. Keep the board supported on the outfeed table as soon as it clears the cutterhead. If the trailing end dips, the outfeed table is probably too low. Raise it in increments of about 0.001 inch and retest.
If the board rides up onto the outfeed table and leaves a ridge or an uncut strip, the table is too high. Lower it slightly. A table that is only a few thousandths high can produce a noticeable ridge, especially on narrow stock.
Also inspect the board for a hollow at the trailing end, a common sign of poor outfeed support or incorrect hand pressure. Do not press down hard on the outfeed side during the cut; let the table support the board. Once the cut is clean, lock the table and record the setting if your jointer has a scale.
When to Replace or Upgrade Tools
A basic straightedge is fine for a homeowner who tunes a jointer once or twice a year. Spend more on a precision straightedge or dial indicator if you maintain several machines, install knives frequently, or need repeatable results across a wide cutterhead. The expensive option saves time only when the rest of the jointer—knife pockets, table ways, and locks—is in good condition.
If adjustment repeatedly drifts, the problem is probably mechanical rather than measuring. Check loose table locks, worn elevation parts, uneven knife clamping, and a cutterhead that is not seated correctly. Fix those faults before making finer adjustments; no measuring gadget can compensate for a table that moves during use.
