Router bit types and profiles

What the common router bits cut, how a bearing guides them, and the speed rules bit makers agree on. For the maximum speed of a given bit, use the router bit speed calculator.

Bit types and what they cut

Straight: Flat-bottomed grooves, dadoes and rabbets, and cleaning up edges against a guide.
Spiral (upcut, downcut, compression): A straight cut with helical flutes. Upcut pulls chips up and out; downcut pushes them down for a clean top face; compression does both, for a clean face on each side of sheet goods.
Flush trim: A bearing the same diameter as the cutter rides on a template or a finished edge, so the cut matches it exactly.
Pattern (template): Like flush trim, but with the bearing on the shank side, so the template can sit on top of the work.
Rabbeting: A cutter with interchangeable bearings that set how deep the step is cut into the edge.
Roundover and bead: Rounds a square edge to a given radius; a beading bit leaves a small step (a fillet) as well.
Chamfer: Bevels an edge at a fixed angle, most often 45°.
Cove: Cuts a concave quarter-round into an edge, the inverse of a roundover.
Ogee and Roman ogee: An S-shaped decorative edge, a curve that turns from convex to concave.
Core box and V-groove: Round-bottomed and V-bottomed grooves for flutes, lettering and decoration.
Dovetail: An angled cutter for dovetail joints and sliding dovetails, used with a jig or a router table.
Keyhole: Cuts an undercut slot so a screw head can hang a frame flush to a wall.
Rail and stile, raised panel: Matched sets for frame-and-panel doors: one cuts the frame joint, the other shapes the panel edge.

Bearings, shanks and profiles

Edge-forming bits (roundover, cove, ogee, chamfer, rabbeting) usually carry a ball bearing on the tip that rolls along the edge of the work, so no fence is needed. The shank is the plain round part held in the router's collet; it must match the collet size, often 1/4 in or 1/2 in. A bit's profile is the shape it leaves on the edge, and its cutting diameter is the widest part of the cutter, which is the size the speed charts go by.

Speed

The larger the bit, the faster its edge travels at the same RPM, so big bits run slower. The rules below come from bit makers' and a router maker's own guidance.

Never run a bit faster than the maximum speed marked on it or its package; a bit run over its rated speed can break and fly apart.
3 sources agree , sources [1, 2, 3]
Bigger bits need lower speed: every chart here steps the maximum down as the diameter grows, because the edge of a bigger bit travels faster at the same RPM.
4 sources agree , sources [1, 4, 3, 5]
DeWALT: do not use bits larger than 2-1/2 in in diameter in the DW616 or DW618, and follow the bit maker’s speed.
One source: DeWALT, the maker of that router , sources [6]

Sources