Which router bit do I need for what I want to do?
Eight bits that cover almost all home routing, what shape each produces, and why a bearing changes how a bit is used rather than what it cuts.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 4 min
Short answer
Start from the shape you want, not the bit name. Square groove or rebate: straight bit. Softened edge: round-over. Angled edge: chamfer. Decorative edge: cove or ogee. Trim one surface level with another: flush-trim. Copy a template: template bit or a guide bush. Decorative line: V-groove. Buy them one job at a time.
Router bits are sold in sets of thirty because that is how they sell, not because that is how they are used. In practice a straight bit, a round-over, a chamfer and a flush-trim bit will cover the first two years of most people's routing, and buying good versions of those four beats a box of thirty poor ones.
Step by step
- Choose a straight bit for anything square-sided.Grooves, housings for shelves, rebates cut with a fence, mortises, and rough waste removal in a template. Buy two or three sizes matched to what you cut — a bit the exact thickness of your usual sheet material is the most useful bit you will own.
- Choose a round-over for softening an edge.A concave cutter with a bearing that turns a square arris into a quarter circle. It is the standard treatment for shelf fronts, worktop edges and anything that gets handled. The radius is the specification — small radii soften, large radii become a visible detail.
- Choose a chamfer for an angled edge.Cuts a flat bevel, usually 45 degrees, with a bearing following the edge. Crisper looking than a round-over, and the standard way to break the edge on a frame or a post.
- Choose a cove or an ogee for a moulded edge.A cove cuts a concave hollow; an ogee cuts an S-curve. Both are bearing-guided and both are used for shelf edges, plinths and anything that wants to look like joinery rather than carpentry.
- Choose a rebate bit for a step along an edge.A straight cutter with a bearing below it. The bearing diameter sets the width of the rebate, and many are sold with a set of interchangeable bearings so one bit cuts several widths.
- Choose a flush-trim bit for levelling one thing with another.A straight cutter with a bearing exactly the same diameter as the cutter, mounted at the tip. The bearing runs on the lower surface and the cutter trims everything above it exactly flush — laminate, edge banding, an oversize panel glued to a substrate.
- Choose a template bit for pattern copying.The same idea with the bearing at the top, above the cutter, so the bearing runs on a template clamped on top of the work. Combined with a template it produces identical parts indefinitely.
- Understand what carbide versus HSS means.High speed steel bits are cheap and cut cleanly when new, but blunt very fast in man-made board. Tungsten carbide tipped (TCT) bits cost more and last many times longer, which makes them cheaper per cut. Buy TCT for anything you will use twice.
- Match the shank to the job.A 1/2in shank flexes far less than a 1/4in one, so it cuts cleaner and is safer, and any large-diameter profile bit should be 1/2in. Small bits are often only made in 1/4in, and that is fine at that size.
- Look after them.Bits blunt from heat and from resin build-up as much as from wear. Clean resin off with blade cleaner and a brass brush, store bits so the cutting edges cannot touch each other or anything metal, and never leave a bit in a collet between jobs.
Tips
- Cutting man-made board — MDF, chipboard, plywood — is far harder on a bit than solid timber because the glue is abrasive. Expect bits to blunt several times faster.
- A bit's stated diameter is nominal. If you are cutting a housing to fit a specific board, cut a test slot and measure it rather than trusting the marking.
- Bearings are replaceable and they do wear and seize. A seized bearing burns a stripe down the edge of the workpiece — check it spins freely before every job.
- Compression and down-cut spiral bits give a cleaner edge on veneered and melamine-faced board than a straight bit, at a higher price. Worth it for visible edges.
Common mistakes
- Buying a thirty-piece boxed set — Most of the profiles are never used, and the bits in a cheap set are usually HSS or poorly brazed carbide that dulls quickly.
- Using a large-diameter bit at full speed — The rim speed becomes dangerous and the cut burns. Large bits need the router's speed turning down.
- Leaving a bit fully seated against the bottom of the collet — It should be inserted fully then withdrawn slightly before tightening, so the collet grips the shank rather than the bit bottoming out.
Questions people ask
What is the difference between a flush-trim bit and a template bit?
Only where the bearing sits. Bottom bearing (flush-trim) follows the surface below the cutter; top bearing (template) follows a pattern above it. Some bits have both and can be used either way up.
Can I use router bits in a drill?
No. Router bits are designed for speeds a drill cannot reach and a drill chuck cannot hold them safely. It is one of the genuinely dangerous improvisations in DIY.
How do I know when a router bit is blunt?
The cut burns where it used to be clean, the surface off the cutter becomes fuzzy rather than crisp, the router needs pushing, and the noise changes. Carbide bits can sometimes be resharpened by a service; small ones rarely justify it.