How do I round over or chamfer an edge with a router?

The easiest routing job there is, and the four details that separate a crisp professional edge from a wavy one with burn marks and a step at each end.

Difficulty: beginner
Time: 20 min
Read: 4 min

Short answer

Fit a bearing-guided round-over or chamfer bit, set the depth so the bearing runs on the face below the cut and the profile just meets the surface without leaving a step, and feed anticlockwise round the outside of the board in two passes. Do the end grain first and the long grain last, so the final passes remove the corner blow-out that end grain always causes.

What you'll need

Router, ideally a palm router
Bearing-guided round-over or chamfer bit
Clamps or a non-slip mat with stops
Scrap for test cuts
Eye, ear and dust protection

Step by step

Prepare the edge first.A bearing copies whatever it runs on. Every dent, saw mark and bump in the edge will be reproduced exactly in the profile, so plane or sand the edge straight and smooth before routing it. This is the step people skip and then blame the router for.
Fit the bit and set it against the workpiece.Insert the bit fully into the collet, withdraw it a couple of millimetres, and tighten. Stand the router on the workpiece and set the depth by eye so the profile will just blend into the face.
Test on scrap of the same thickness.The difference between a perfect round-over and one with a small step or ridge at the top is under a millimetre of depth. Cut scrap, look at it in a raking light, and adjust.
Set the depth so there is no step.If the bit is too high, it leaves a fine ridge along the top of the profile — router snipe on an edge. Too low and it cuts into the face, leaving a shallow scoop. The correct setting is where the curve runs out exactly at the surface.
Cut in two passes for a large radius.A small round-over can be done in one. Anything larger, or anything in hardwood, comes out better with a first pass at part depth and a light final pass, which removes the marks the first left.
Route the end grain first.Do the two end-grain edges before the two long-grain ones. End grain blows out a small chip at the far corner as the cutter leaves, and the subsequent long-grain passes cut that damage away.
Feed anticlockwise round the outside.Standing over the board, work anticlockwise so the cutter meets the timber against its own rotation. Inside an aperture, reverse to clockwise.
Keep the base flat and the bearing in contact.Two failures produce a wavy profile: letting the base tip so the bit rocks, and letting the bearing lift off the edge. Press the base down and in, and keep moving steadily.
Do not stop mid-edge.The cutter burns the moment it stops. Plan each pass as a single continuous movement from off one end to off the other.
Finish lightly.A crisp routed profile needs very little sanding — one pass with a fine abrasive to break the two arrises where the profile meets the face. Heavy sanding rounds and blurs the shape the router just made.

Tips

Rounding over the corners of a board where two profiled edges meet takes a moment with a small block and fine paper, and it is the detail that makes a piece feel finished.
For a narrow workpiece, mount the router in a table instead. Trying to balance a router on a 40mm edge by hand is where profiles go wavy.
A chamfer shows every wobble more clearly than a round-over does, because a flat surface catches the light. If you are new to the tool, start with a round-over.
Softening the top edge of a worktop or a shelf with a small round-over stops the finish wearing off the arris, which is where every painted edge fails first.

Common mistakes

Routing an edge that has not been trued first — A bearing follows the edge exactly, so the profile reproduces every bump. Prepare the edge, then profile it.
Doing the long grain first — The end-grain passes then blow out the corners of the profile you have just finished, and there is nothing left to cut the damage away.
Setting the bit slightly too high — It leaves a fine ridge that you cannot see now and will see clearly the moment it is painted or oiled.
Pausing to reposition halfway along an edge — The bit scorches at the exact spot it stops, on the visible face of the work.

Questions people ask

Why is there a step or ridge along my round-over?

The bit is set fractionally too high, so the profile does not run out at the surface. Lower it a fraction and take a second light pass along the same edge.

Which radius round-over should I use?

Small radii soften an edge without being noticed, which is what you usually want on shelves and furniture. Larger radii become a visible design feature and remove enough material to change the look of a board. Test on an offcut and look at it in place.

Can I round over plywood edges?

You can, but the exposed plies look like plies — a round-over emphasises the layered edge rather than hiding it. Edge banding or a solid timber lipping first, then a round-over on that, is the usual answer.