The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →A loose-fitting dado can be repaired with a veneer or matching-wood shim, a wedged spline for a gap smaller than 1/16 inch, or a glued-in filler strip followed by recutting for a larger gap. Choose based on the gap, how visible the repair will be, and whether you can safely recut the joint.
Choose a repair for the gap
WOOD Magazine’s 2016 guide describes three approaches. It does not compare their strength or durability, so choose by the size and location of the gap and the work your repair requires.
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Ridge Carbide 6 pcs 100mm, 1-3/8" Bore Magnetic Shim Kit, 2 pcs Each of .010", .012", .015" | $32.67 | Buy on Amazon |
| Repair | When to use it | Work involved |
|---|---|---|
| Veneer or matching-stock shim | To fill a remaining gap where a thin fitted piece can close it | Fit and glue the piece, then trim or sand it smooth |
| Wedged spline | WOOD specifies this method for gaps smaller than 1/16 inch | Cut a slot in the inserted board’s end and tap in a beveled spline |
| Similar-wood filler strip and recut | For a gap too wide for the first two repairs | Glue in a strip, flatten it, then recut the dado to the correct width |
These methods and dimensions are from WOOD Magazine Staff’s “Cures for Loose Dadoes,” published September 27, 2016.
Fit a veneer or matching-stock shim
- Fit a piece of veneer or rip a thin shim from matching stock so it fills the gap.
- When practical, place the shim on the less visible side of the joint.
- Glue the shim to the shelf and the dado wall.
- After the glue has set, trim or sand the shim flush. WOOD Magazine describes scoring a fitted shim flush with a utility knife, removing it, and trimming it on the workbench before installing it.
This approach addresses the gap with a fitted piece rather than changing the dado’s width.
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- Guaranteed not to fall off or get hung up on your saw's arbor.
- Holds additional metal or plastic shims to dado blades.
- Includes two (2) each of .010", .012", and .015" thick shims.
- Shims measure 100mm Outside Diameter x 1-3/8" ID (bore diameter). Can be cut down to smaller diameter if required.
- These magnet shims are very thin and not very "strong". Please make sure the blade and magnet are VERY clean before applying. If the magnetic shim does not "stick" at first, please flip it over and try the opposite side.
Use a wedged spline for a gap under 1/16 inch
WOOD Magazine specifies a wedged spline when the gap is smaller than 1/16 inch. The spline spreads the ends of the inserted workpiece to tighten the fit.
- Cut a slot centered on the end of the inserted board. The guide specifies a slot 1/8 inch wide and 1/2 to 3/4 inch deep. It describes a slotting cutter, with a 1/8-inch table-saw kerf as an alternative.
- If using a table saw for a long or unwieldy workpiece, support it with a tall auxiliary fence, as the guide recommends.
- Make a spline with 5-degree bevels on each face and a narrow edge that matches the slot thickness.
- Tap the spline into the slot gently. Trim or sand it as needed to achieve a fit.
Fill and recut a wider gap
- Glue a strip of similar wood into the dado, matching its color and grain as closely as possible.
- Orient any exposed sliver of filler toward the less visible side when the layout allows.
- Plane or sand the filler flush with the surrounding surface.
- Before recutting the dado, make test cuts in scrap to confirm the width and fit.
- Once the test fit is right, recut the dado to the correct width.
This repair involves recutting, so it requires a suitable setup for the workpiece and the machine. OSHA’s woodworking machine-hazards guidance says that when guards cannot be used during operations such as dadoing, suitable jigs, combs, or featherboards should be provided. Follow the machine manufacturer’s instructions and safeguards for your specific setup, and let glued joints dry before working on the stock.
Quick Recap
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