Knowing how to cut a dado with a router gives you accurate shelf dados, cabinet partitions, and bookcase grooves without a dedicated dado stack. A straight bit, a straightedge or jig, and patient depth settings produce flat-bottomed channels that fit plywood or solid stock better than many saw-cut dados. This guide covers layout, guides, bit width strategy, and the multi-pass method that protects your workpiece.
Guides
How to Cut a Dado with a Router
How to cut a dado with a router using a straight bit, edge guide or jig, depth stops, and clean multiple passes for shelves.
Dado basics for router work
A dado is a groove cut across the grain; a groove runs with the grain. Routers cut both the same way—the difference is stock orientation and grain behavior. Aim for a fit that seats the shelf with light hand pressure: too tight forces the case out of square, too loose leaves a weak glue joint. Always size the dado to the actual shelf thickness, not the nominal 3/4 in label on plywood.
What you need
- Plunge router or fixed-base router with reliable depth control
- Straight bit sized for the dado, or a smaller bit for multiple passes
- Clamped straightedge, commercial dado jig, or edge guide
- Calipers or a scrap offcut of the shelf stock for fit tests
- Clamps, marking knife, and square
- Dust collection or a shop vac hose near the cut
How to cut a dado with a router
01
Measure the shelf and mark the dado
Measure the shelf thickness with calipers in a few spots. Mark the dado location with a square and knife so pencil fuzz does not widen your layout. Transfer marks to both faces if the dado must stop short of a finished edge. Confirm left/right orientation so mirrored case sides stay consistent.
02
Choose bit width strategy
If you have an exact-width bit that matches the shelf, use it. More often, plywood is undersize—use a slightly narrower bit and sneak up on width with a second pass after a fit test. Spiral upcut bits clear chips well in deep dados; straight two-flute bits leave a cleaner bottom for shallow work. Prefer 1/2 in shank bits when the cut is deep or long.
03
Set up the guide
Clamp a straightedge so the bit’s cutting edge lands on your layout line. Account for the offset from base edge to cutter—make a setup scrap and mark the true offset once for that base and bit. Commercial dado jigs that sandwich the router eliminate offset math. Keep the guide long enough that the router base stays fully supported at the start and finish of the cut.
04
Set depth and cut in passes
Typical shelf dados are about one-third the thickness of the side—often 1/4 in deep in 3/4 in stock. Do not take a full-depth cut in one plunge on dense hardwood. Set a shallow first pass, cut the full length, then deepen in stages. Keep the base flat against the panel and feed against bit rotation for control.
05
Tune the fit
Test the shelf in the dado. If it is tight, shift the guide a hair and take a skim pass on the tight side only. If it is loose, you may need a thicker shelf, veneer shim, or a glue-and-spline rescue later—so err on the tight side of scrap tests first. Clean the dado bottom before glue-up so chips do not hold the shelf high.
Stopped dados and through dados
Through dados are simpler: enter and exit the edges. Stopped dados hide the groove from the front of a bookcase. For stopped cuts, mark the stop, plunge inside the waste, rout to the stop, and square the rounded bit end with a chisel. Practice the stop on scrap so you do not overshoot a visible face.
Common dado mistakes
- Sizing to nominal plywood thickness instead of measured thickness
- Taking full depth in one pass and burning or wandering
- Letting the router tip into the cut at the start or end
- Skipping scrap fit tests before cutting both case sides
- Using a dull bit that leaves a wavy, burned floor
Router vs table saw dado
A table saw dado stack is fast for repetitive through dados on solid stock. A router shines on large panels that are awkward on the saw, on stopped dados, and when you need a flat bottom without a dado set. Many shops use both: saw for production runs, router for panels and fine-tuned plywood fits.
FAQ
01
What bit is best for cutting a dado with a router?
A sharp straight or spiral bit is the standard choice. Match width to the shelf when possible, or use a narrower bit and sneak up on fit. Spiral upcuts clear chips in deep dados; straight bits often leave a cleaner shallow floor.
02
How deep should a shelf dado be?
About one-third of the side thickness is a common rule—roughly 1/4 in deep in 3/4 in case stock. Deeper cuts can weaken the side; shallower cuts reduce glue surface. Adjust for heavy loads and material strength.
03
Can I cut a dado with a palm router?
Yes for shallow, narrow dados in softer materials. Deep or wide dados in hardwood are more stable with a mid-size plunge router and a solid guide. If the tool feels underpowered or chatters, take lighter passes or step up in router size.
04
How do I keep both cabinet sides identical?
Clamp both sides together and cut dados as a pair when the design allows, or use the same guide setup and story stick for mirrored layouts. Mark insides clearly so you do not create two left sides.
05
Why does my dado have a rough bottom?
Dull cutters, too-fast feed, poor chip clearance, or a router base that tips can leave ridges. Slow down, sharpen or replace the bit, add dust extraction, and keep the base fully supported on the panel.
06
Should I glue a dado joint?
Yes for most casework—glue plus mechanical fit makes a strong shelf joint. For adjustable shelves you want holes or pins instead of fixed dados. Dry-fit the whole case before glue so dados and partitions align.
07
How do I cut a dado wider than my largest bit?
Make a first pass on one layout edge, then shift the guide and cut the opposite edge, clearing the middle last. Use a fit scrap of the shelf stock between passes so the final width matches the real part.