How to Square a Jointer Fence to the Cutterhead Table
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A jointer fence is square when a reliable square shows no gap between the fence face and the cutterhead table. Check it at both ends of the fence: a fence can be square near the knives and still be twisted along its length. A small error can turn into a beveled edge or a board that rocks against the fence, so verify the setup before relying on it for edge-jointing.
Contents
Tools and safety
Unplug the jointer before putting a square near the cutterhead or reaching for fence adjustments. If the machine has a magnetic switch, unplug it rather than relying on the switch being off. Keep hands clear of the knives; do not rotate the cutterhead by pushing on a blade.
Use a machinist’s square or a good engineer’s square with a blade long enough to reach across the table and up the fence. A 6-inch square is often adequate on small jointers, but a longer square makes a slight error easier to see. A framing square is usually too large and may not be accurate enough for this check. A 6-inch machinist’s square is a sensible choice for most shop setups.
Clean the table and fence first. Dust, pitch, or a chip trapped under the square can create a false reading. Also check the square against a known straight reference or flip it against the same surface: if the gap changes sides, the square may be out of true.
Check the fence at both ends
Move the fence to 90 degrees using its scale or stop, but treat the scale as a starting point, not proof. Set the square on the outfeed table with its stock flat against the table and its blade against the fence. Avoid resting it over a gap or directly on a knife. Bring it close to the cutterhead without touching the cutting edge.
Look for daylight between the square and fence. Check near the front of the fence, then near the back, using the same table surface as your reference. If the square contacts at one end but leaves a gap at the other, the fence is twisted or the table, square, or fence face is not giving a trustworthy reference. A consistent gap across the fence suggests the fence is simply not at 90 degrees.
For a more controlled check, use a feeler gauge to estimate the gap. For example, a 0.005-inch leaf that slips in at one end but not the other shows a measurable twist. Don’t chase tiny readings until you have cleaned the surfaces and confirmed the square. On a jointer, chips and burrs can easily exceed the error you are trying to measure.
Adjust the fence
Fence mechanisms differ. Some have a 90-degree stop screw; others use a trunnion, a pivot bolt, or adjustable support brackets. Find the manual’s adjustment procedure before loosening hardware. Mark the current position with pencil or tape so you can return to it if the adjustment goes the wrong way.
If the fence is consistently out of square, adjust its 90-degree stop or pivot in small increments. Hold the fence against the stop, tighten the lock, then recheck. Tightening can pull the fence slightly out of position, so take the final measurement with the lock engaged. If one end reads square and the other does not, look for a twist adjustment or a loose mounting point rather than moving the stop alone.
Some fences are not adjustable for twist. In that case, check for a bent fence, damaged mounting surfaces, or debris between the fence and its support. Don’t shim a fence with loose paper or cardboard; it can compress or shift. A properly fitted metal shim may be appropriate if the manufacturer allows it, but a distorted casting or damaged support may need service or replacement.
Choosing a checking tool
| Tool | Best use | Trade-off |
|---|---|---|
| Machinist’s or engineer’s square | Routine 90-degree checks and fence setup | Costs more than a basic square, but is compact and easy to verify |
| Combination square | General shop work and quick checks | Useful and inexpensive; blade can shift or be less dependable if worn |
| Feeler gauges | Estimating a visible gap after squaring | Helpful for comparing ends, but do not establish 90 degrees by themselves |
A decent combination square is fine for occasional setup if its blade is straight and its head locks securely. If you already own one, check it before buying another. For frequent machine setup, a dedicated precision engineer’s square is easier to handle and less likely to move during the check.
Confirm with a test cut
After the fence reads square, make a shallow pass on a straight, flat board with a clean edge. Keep the board firmly against the fence and table, using push blocks and safe feeding technique. Check the jointed edge with the square in several places. A test cut can expose a problem that a static check misses, such as a fence that shifts under pressure or a table surface that is not clean.
If the edge is beveled, first confirm that the board was held consistently and that the square itself is true. If the bevel changes from one end of the board to the other, suspect fence twist or inconsistent pressure. If it is uniform, the fence may be set off 90 degrees. Do not use the fence to compensate for a different problem, such as a table-height issue or knives that are not set correctly.
Keep the setting reliable
Recheck the fence after moving it, tightening hardware, or taking a hard knock. Dust buildup at the fence pivot and table edge can affect repeatability, so clean those areas before setup. Store the square where its blade cannot be bent, and periodically verify it against a known reference.
A small, repeatable gap matters more than a reading that changes every time you check. Clean, lock, measure, and test-cut in that order. If the fence will not hold square after adjustment, stop using it for precision edge work until you find the loose or damaged part.
