Key takeaways
- A fence out of parallel with the blade by even 0.010 inch causes trouble out of proportion to the number. If it angles toward the blade at the back, the board gets pinched against the rising rear teeth, which burns…
A fence out of parallel with the blade by even 0.010 inch causes trouble out of proportion to the number. If it angles toward the blade at the back, the board gets pinched against the rising rear teeth, which burns the edge, dulls the blade, and sets up the classic kickback. If it angles away, the cut wanders and glue joints show gaps. On a cast iron saw the table and trunnions are heavy and stable, so once the blade is aligned to the miter slot and the fence to the slot, the setting holds for months. The job takes about an hour the first time and 15 minutes after that.
What You Need
| Item | Why | Optional? |
|---|---|---|
| Combination square or machinist square (12 inch) | Measures the gap between the miter slot and the fence at front and back | No |
| Dial indicator with a miter-slot jig, or a feeler gauge set | Reads alignment to 0.001 inch instead of eyeballing | Yes, but strongly recommended |
| Hex keys and wrenches that fit your fence and trunnion bolts | Most fences adjust with 4 to 6 mm hex screws or 7/16 inch bolts | No |
| Straightedge, 24 to 36 inch | Checks that the fence face itself is flat before you align it | No |
| Fine-tip marker | Marks one blade tooth so you measure the same tooth front and back | No |
| Scrap plywood, 12 x 24 inch, straight factory edge | Test rips confirm the setting on real wood | No |
| Replacement or upgrade fence system | If the stock fence will not hold a setting; a 46-inch rip fence system such as the O’SKOOL kit runs around $179.99 | Yes |
Step-by-Step
Step 1: Unplug the saw and clean the table (5 minutes)
Pull the plug, not just the switch. Remove the blade guard and riving knife if they get in the way of the measuring tools. Scrape pitch and sawdust out of the miter slots with a putty knife, then wipe the cast iron with mineral spirits. A 1/32 inch chip of wood in a slot will throw every measurement off.
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Step 2: Check the fence face for flatness (5 minutes)
Lay the straightedge along the face of the fence and look for light gaps. Most stamped-steel or extruded aluminum fences are flat within 0.005 inch, but a fence with a bow of 0.02 inch or more cannot be aligned; it will be parallel at the ends and off in the middle. If yours has a bowed laminate or UHMW face, shim it or replace the face before continuing.
Step 3: Align the blade to the miter slot first (15-20 minutes)
The fence is aligned to the miter slot, so the slot and blade must agree first. Raise the blade fully and mark one tooth. Rotate that tooth to the front of the table opening and measure from the left miter slot to the tooth face with a dial indicator in a slot jig, or a combination square locked against the tooth. Rotate the same tooth to the rear and measure again. The readings should match within 0.003 inch for a cabinet saw or 0.005 inch for a contractor saw. If not, loosen the trunnion bolts, tap the assembly with a wood block and mallet, re-measure, then snug the bolts to about 25 to 30 ft-lb and check once more, since tightening often shifts things a thousandth or two.
Step 4: Lock the fence near the blade and measure front and back (10 minutes)
Set the fence about 3 inches from the blade and lock it. Measure from the miter slot edge to the fence face at the front of the table and again at the rear, using the same slot edge each time. Write both numbers down. On a well-aligned saw they will match, or the rear reading will be 0.002 to 0.005 inch larger. That tiny rearward opening, about the thickness of a sheet of paper over 24 inches, is deliberate: it gives the cut edge a whisper of clearance from the back of the blade and reduces burning.
Step 5: Adjust the fence (10-15 minutes)
On T-square fences found on most cabinet and hybrid saws, the adjusters are two or four hex screws on the fence head where it clamps the front rail. Loosen them a quarter turn, pivot the fence tail until the rear measurement is where you want it, and snug them evenly. On older rail-and-clamp fences, adjust the set screws bearing on the rear rail. Move in small increments; a 1/8 turn can shift the tail 0.010 inch. Relock, re-measure, and repeat until the numbers hold through three lock-and-release cycles.
Step 6: Check the fence is square to the table (5 minutes)
Stand a machinist square on the table against the fence face. Any lean shows as a gap at the top or bottom. Most fences have a pair of set screws under the head to correct this. A lean of 0.010 inch over a 3-inch fence height is acceptable for general work; for joinery, get it under 0.005 inch.
Step 7: Test rip and verify (10 minutes)
Plug in, reinstall the riving knife, and rip the plywood scrap to about 6 inches wide. Burn marks near the rear of the cut mean the fence is pinching; a fuzzy or stepped edge means it is opening too far. Measure the offcut at both ends with calipers; a difference under 0.005 inch over 24 inches is excellent.
Step 8: Wax and record (5 minutes)
Wax the table and fence rails so the fence glides and locks consistently, and write your front and rear readings with the date on tape inside the cabinet for next time.
Mistakes to Avoid
Measuring to the blade plate instead of a marked tooth: plates can wobble 0.005 inch or more. Aligning the fence to the blade instead of the slot: if the blade is out, you build the error into the fence too. Measuring different slot edges at front and back: slots are not always a constant width. Cranking adjustment screws tight before verifying: uneven torque twists the head. Trusting the fence scale afterward without recalibrating the cursor.
How Often
Check parallelism monthly if you use the saw weekly, and any time you notice burning or after moving the saw. Cast iron saws with T-square fences generally hold within 0.003 inch for six months or more; contractor saws with the motor hanging off the back drift faster. Always re-check after a kickback event, which can shift a trunnion.
When to Call a Pro or Replace
If the trunnion bolts are seized or the cast iron mounting ears are cracked, stop; trunnion work on a cabinet saw means lifting a 300 to 500 pound machine, and a saw technician charges $150 to $400 for a full alignment. Replace the fence when the face is bowed more than 0.02 inch, the locking cam is worn so the fence shifts when locked, or the head has cracked. Aftermarket T-square rip fence systems in the 46 to 52 inch range cost $180 to $400 and bolt to the original front rail holes; for anyone upgrading in 2026, a quality fence is usually the single best accuracy improvement for a saw under $1,500.
FAQ
How much fence misalignment is acceptable?
Parallel to the miter slot within 0.003 inch, or opening away from the blade at the rear by up to 0.005 inch over the table length. Any toe-in toward the blade at the rear is unacceptable because of kickback risk.
Do I really need a dial indicator?
No, but it turns a guessing game into a two-minute measurement. A combination square and a set of feeler gauges will get you within 0.005 inch if you are careful. Dial indicator jigs for miter slots cost $30 to $60 and pay for themselves the first time you diagnose burning.
Why does my fence move when I lock it?
The locking cam or the rear glide pad is worn, or the front rail is dirty. Clean the rail, wax it, and adjust the rear pad so the fence rests on it lightly before locking. If it still shifts more than 0.003 inch, the head mechanism is worn and replacement is the practical fix.
Should the fence be perfectly parallel or slightly open at the back?
Slightly open, by 0.002 to 0.005 inch, is the safer setting for ripping solid wood. Dead parallel is fine for plywood and gives marginally cleaner edges, but the margin for error is zero.
