Router Bit Guide: Straight, Flush, and Profile Bits Explained

A router is only as capable as its bits. Understanding router bit types, their applications, and how to choose quality tooling will dramatically expand what you can accomplish in your shop. This guide covers the essential bit types every woodworker should know, from basic straight bits to specialized profile cutters.

Straight Bits: The Foundation of Router Work

Straight bits are the workhorses of any router bit collection. These simple cylindrical cutters create flat-bottomed grooves, dadoes, rabbets, and mortises. Available in diameters from 1/8 inch to over 1-1/2 inches, straight bits handle everything from delicate inlay work to large panel rabbets.

Standard straight bits feature two flutes (cutting edges) and work well for most applications. Single-flute bits remove material faster but leave rougher surfaces, while three-flute bits produce smoother cuts at the expense of slower material removal.

For template work and precision cuts, look for straight bits with bearing guides. Bottom-bearing straight bits follow templates placed beneath your workpiece, while top-bearing versions reference templates on top. This simple addition transforms a basic straight bit into a precision pattern-cutting tool.

Flush Trim and Pattern Bits

Flush trim bits feature a bearing the same diameter as the cutting edge, allowing you to trim one piece perfectly flush with another. These are essential for template routing, trimming edge banding, and cleaning up bandsaw cuts to a reference surface.

Top-bearing flush trim bits reference the template or guide piece on top of your workpiece, while bottom-bearing versions (often called pattern bits) reference templates underneath. Having both types in your collection gives you flexibility for different setups and workpiece configurations.

Bit length matters with flush trim work. Choose bits long enough to cut through your workpiece material plus provide adequate bearing contact with your template. Most woodworkers keep several lengths on hand for different material thicknesses.

Edge Profile Bits: Roundover, Chamfer, and Ogee

Roundover bits create smooth, radiused edges and rank among the most-used profile bits. Common sizes include 1/8, 1/4, 3/8, and 1/2-inch radii. Larger roundovers can create a bullnose profile when run on both faces of a board. These bits soften sharp edges, making furniture comfortable to touch and less prone to chipping.

Chamfer bits cut angled edges, with 45 degrees being the most common angle. Chamfers add visual interest, help with assembly alignment, and prevent edge damage. Variable-angle chamfer bits let you cut angles from 15 to 45 degrees with a single bit.

Ogee bits create the classic S-curve profile found on traditional furniture and architectural moldings. Roman ogee and classic ogee patterns differ slightly in their curves but both produce elegant, formal edges. These bits transform plain boards into professional-looking trim and molding.

Other useful profile bits include cove bits (concave curves), beading bits (raised half-round profiles), and edge-forming bit sets that combine multiple profiles for complex molding creation.

Spiral Bits: Up-Cut, Down-Cut, and Compression

Spiral bits feature helical cutting edges that shear material rather than chopping it, producing superior surface quality and more efficient chip evacuation.

Up-cut spirals pull chips upward out of the cut, ideal for mortising, pocket cuts, and through-cuts where chip clearance matters. However, they can cause tearout on the top surface of your workpiece.

Down-cut spirals push chips downward into the cut, leaving a clean top edge. These excel at dadoes, grooves, and any cut where the visible surface faces up. The tradeoff is slower chip evacuation and potential for burning in deep cuts.

Compression spirals combine up-cut geometry at the bottom with down-cut at the top, producing clean edges on both faces. CNC operators favor these for cutting plywood and veneered panels, and they work equally well for handheld routing when both surfaces are visible.

Shank Sizes: 1/4-Inch vs 1/2-Inch

Router bits come in two primary shank diameters: 1/4-inch and 1/2-inch. Shank size significantly affects performance, safety, and bit longevity.

Half-inch shank bits are stronger, more stable, and less prone to deflection and vibration. They run cooler, last longer, and produce cleaner cuts, especially with larger diameter profiles. Always choose 1/2-inch shank bits when your router accepts them.

Quarter-inch shank bits fit smaller routers and excel with detailed work requiring smaller diameters. Laminate trimmers and compact routers typically only accept 1/4-inch shanks. These bits work fine for light-duty operations but can struggle with aggressive cuts in hardwoods.

Carbide vs HSS: Material Matters

Modern router bits feature either high-speed steel (HSS) or carbide cutting edges. Carbide costs more but offers dramatically better performance and longevity.

Carbide-tipped bits stay sharp 10 to 25 times longer than HSS in typical use. They maintain edge quality when cutting abrasive materials like MDF, plywood, and particle board that quickly dull steel bits. For most woodworkers, carbide is the only sensible choice.

Solid carbide bits (not just tipped) offer even better performance and can be resharpened multiple times. These premium bits cost significantly more but justify their price for production work or frequently used profiles.

HSS bits still make sense for occasional use with soft materials or specialized profiles where carbide options are expensive or unavailable.

Building a Starter Bit Set

Rather than buying a large set with bits you’ll rarely use, build your collection strategically. Start with these essential bits:

Must-have bits: 1/2-inch straight bit (general grooving), 1/4-inch roundover (edge softening), flush trim bit (template work), 45-degree chamfer (decorative edges), and a rabbeting bit with multiple bearings (cabinet backs and panel work).

Next additions: 1/4-inch straight bit (dadoes for plywood), 3/8-inch roundover (larger profiles), pattern bit (template work flexibility), and a Roman ogee for traditional profiles.

Quality over quantity: Invest in quality bits from manufacturers like Whiteside, Freud, CMT, or Amana. Cheap bits dull quickly, produce poor cuts, and can be dangerous. A few excellent bits outperform a drawer full of budget cutters.

Store your bits properly in a dedicated holder that protects the cutting edges. Never let bits touch each other in a drawer where they can chip and dull. With proper care, quality carbide bits will serve you for decades.