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The jig that makes every other project accurate. Built from scrap in an afternoon, using the five-cut method.
| Part | Qty | T × W × L | Material | ✓ |
|---|---|---|---|---|
| Sled base | 1 | 1/2" × 27" × 20" | Baltic Birch Plywood | ☐ |
| Rear fence (the important one) Laminate two pieces of 3/4" for stiffness. This fence is your accuracy — it must be dead straight and stay that way. | 1 | 1 1/2" × 3 1/2" × 27" | Maple | ☐ |
| Front fence Structural only — it holds the two halves of the sled together after the blade cuts through. It does not need to be square. | 1 | 1 1/2" × 3 1/2" × 27" | Maple | ☐ |
| Runners Measure YOUR miter slots. They are not all 3/4". | 2 | 3/8" × 3/4" × 24" | Maple or UHMW | ☐ |
| Item | Qty | ✓ |
|---|---|---|
| Baltic birch plywood, 1/2", for the base Baltic birch, not construction ply. It's flat, it stays flat, and flatness is the entire point of the jig. | 0.25 sheet | ☐ |
| Hardwood, 3/4", for the fences (Maple) Must be straight and stay straight. A bowed rear fence makes a bowed cut. | 3 board feet | ☐ |
| Hardwood or UHMW for runners Sized to slide in your miter slots with zero slop and no binding. UHMW ignores humidity; wood runners swell in summer. | 2 each | ☐ |
| Wood screws, #8 x 1-1/4" | 16 each | ☐ |
| Paste wax On the sled's underside. Makes it glide. | 2 oz | ☐ |
Overall cost: $. Lumber varies by region, species, and season, so we give a band rather than a figure.
Tools: Table Saw. Materials: Hardwood or UHMW for runners
Mill the runners to slide in your miter slots smoothly with no side-to-side play and no binding. Sneak up on the width — take a shaving, test, repeat.
They should slide under their own weight but not rattle. Slop in the runners is slop in every cut you'll ever make on this sled.
Tools: Combination Square, Spring Clamps. Materials: Baltic birch plywood, 1/2", for the base, Wood screws, #8 x 1-1/4"
Set the runners in the slots with a few coins or washers underneath to lift them slightly proud of the table. Put glue on top of the runners, lay the base down on top, aligned square-ish to the blade, and press.
Once tacked, flip and screw through the base into the runners. The coins guarantee the base sits on the runners, not on the table.
Tools: Drill / Driver. Materials: Hardwood, 3/4", for the fences, Wood screws, #8 x 1-1/4"
Screw the front fence across the leading edge. This one is purely structural — after you cut the kerf through the sled, it and the rear fence are all that hold the two halves together.
No need to square it to anything.
Tools: Table Saw
Raise the blade and push the sled through, cutting a kerf through the base and into (not through) the front fence.
Stop before you exit the back. You now have a slot that shows exactly where the blade cuts.
Tools: Combination Square, Drill / Driver. Materials: Hardwood, 3/4", for the fences, Wood screws, #8 x 1-1/4"
Position the rear fence roughly square to the kerf. Fasten it with a single screw at one end, so it can still pivot.
That pivot is what lets you dial in perfect square in the next step. Screw it down solid now and you'll be shimming it forever.
Tools: Table Saw
Take a scrap of plywood, roughly square, maybe 12". Label the edges 1-2-3-4.
Cut a whisker off edge 1. Rotate 90° clockwise, cut edge 2. Rotate, cut 3. Rotate, cut 4. Now make a fifth cut on edge 1 again, but take off a piece about 2" wide.
Measure that fifth strip at both ends with calipers. If the ends differ, your fence is off — and by a known amount:
error per inch = (difference) ÷ (4 × length of the strip)
Multiply that by the distance from your pivot screw to the far end of the fence, and that's exactly how far to move the free end. The four rotations multiply the error by 4, which is what makes an unmeasurably small error measurable.
Tap the fence, re-test. Two or three iterations gets you dialed.
Tools: Drill / Driver, Random Orbit Sander, Table Saw. Materials: Paste wax
Once the five-cut says you're square, screw the rear fence down along its whole length. Re-test once more to make sure nothing shifted while you were driving screws.
Cut the kerf the rest of the way through the rear fence. Add a block of wood over the exit point as a blade guard — the blade comes through there and it will find your hand eventually if you don't.
Wax the underside. Then go crosscut something and enjoy a perfect 90° for the first time.