What Router Planes Do That Other Planes Can't

A router plane blade points straight down through the plane body and extends below the sole by an adjustable amount. The sole rides the wood surface surrounding a recess—a dado, hinge mortise, or inlay pocket—while the blade cuts the bottom of that recess. Each pass removes material from the recess floor until it reaches a uniform depth below the reference surface. No other hand plane type works this way because all other planes cut surfaces parallel to the sole rather than perpendicular to it.

The depth adjustment on a router plane determines how far the blade extends below the sole, which directly controls how deep the recess gets cut. Set the blade to extend 1/4 inch below the sole and the plane cuts recesses 1/4 inch deep. Extend it 3/8 inch and you get 3/8-inch deep recesses. This direct depth control creates uniform recess bottoms regardless of how the recess was roughed out initially.

The L-Shaped Blade Configuration

Router plane blades form an L-shape with a horizontal cutting edge at the bottom and a vertical shank rising through the plane body. The cutting edge sits perpendicular to the direction of travel, scraping across the recess bottom rather than slicing along it like bench plane blades do. This scraping action works across all grain directions without caring which way fibers run.

The blade mounts in the plane body with the cutting edge facing forward, backward, or sometimes to the side depending on plane design. The mounting method allows blade rotation to position the cutting edge appropriately for different operations. Some router planes include multiple blade positions within a single body, providing versatility for reaching into various recess configurations.

The blade's vertical shank passes through a clamp or collar in the plane body. Loosening this clamp allows the blade to slide up or down for depth adjustment. Tightening it locks the blade at the desired depth. The mechanism provides precise, repeatable depth control that other plane types can't match because their blades don't extend perpendicular to the sole.

Premium router planes use thick blades (perhaps 1/4 inch square in cross-section) that resist flexing under cutting pressure. Budget versions sometimes use thinner blades that deflect slightly, affecting depth precision. The blade rigidity matters more in router planes than most other planes because any flex directly translates to depth variation in the finished recess.

Hinge Mortise Reality

Hinge mortises represent the classic router plane application. A butt hinge requires a recess exactly the thickness of one hinge leaf—typically 1/16 to 1/8 inch deep. The recess must be flat across its bottom for the hinge to sit flush. Rough out the mortise with a chisel to approximate depth, then clean the bottom to exact depth with the router plane.

The router plane sole rides the door or cabinet face surrounding the mortise. The blade extends into the mortise by the exact hinge leaf thickness. Passes across the mortise bottom remove high spots until the blade takes continuous shavings across the full mortise area. This indicates the bottom has reached uniform depth.

Traditional methods involve chiseling hinge mortises entirely by hand, using careful technique to achieve flat bottoms. This works but requires significant skill and attention. The router plane makes the operation nearly foolproof—set the depth correctly and the plane physically can't cut deeper than intended. The surrounding surface acts as a positive stop.

Door hanging involves installing multiple hinges per door, often three or four. Each hinge needs a mortise cut to identical depth. The router plane maintains consistency across all mortises by using the same depth setting. Chisel work alone struggles to match this repeatability without constant measurement and checking.

Dado and Groove Cleanup

Hand-cut dados and grooves roughed out with saws and chisels rarely come out perfectly flat on the bottom. Variations of 1/64 inch or more appear commonly, creating problems when fitting shelves or panels that need to seat properly. Router planes flatten these bottoms to uniform depth after the rough cutting establishes the channel.

The router plane sole rides the wood surfaces on both sides of the dado. The blade works the dado bottom, taking light passes that remove high spots. The final pass takes continuous shavings, indicating the bottom has reached consistent depth across the full dado length and width.

Stopped dados (ending before the board edge) particularly benefit from router plane work because the stopped end often shows torn or compressed wood from chisel chopping. The router plane cleans this area to the same depth as the rest of the dado, ensuring shelves seat properly at the stopped end.

Machine-cut dados from table saws or routers might seem unnecessary to clean with hand tools, but even power tools sometimes leave slight ridges or variations. Running a router plane through machine-cut dados as a final pass guarantees perfect flatness that glue-ups and panel insertion will appreciate.

Inlay Work Applications

Inlay pockets must reach precise, uniform depths for inlays to sit flush with surrounding surfaces. Too shallow and the inlay stands proud requiring sanding that thins the inlay. Too deep and the inlay sits recessed creating visible gaps. Router planes create the depth precision inlay work demands.

The process involves routing the inlay pocket roughly to depth with chisels or a power router, then using a router plane to bring the pocket to exact final depth. The router plane sole rides the surrounding wood while the blade works only the pocket bottom. This ensures the inlay will sit exactly flush when installed.

Contrasting wood inlays show every depth variation as shadow lines or proud spots. The router plane's ability to create dead-flat bottoms at precise depths eliminates these visual defects. The resulting inlay appears as a continuous surface rather than showing installation flaws.

Metal inlays like brass or pewter demand similar precision. The metal doesn't compress or sand down easily, making initial depth accuracy critical. Router planes provide this accuracy through positive depth stops created by the sole-to-blade relationship.

Tenon Cheek Adjustment

Tenon fitting sometimes requires removing material from tenon cheeks to achieve proper joint fit. The tenon already exists, roughed to approximate dimensions. Final fitting involves removing specific amounts from individual cheek surfaces. Router planes handle this by riding the tenon shoulder while the blade works the cheek surface.

The depth adjustment controls how much material comes off the cheek. Need to remove 1/64 inch? Set the blade to extend 1/64 inch below the tenon shoulder height and make passes across the cheek. The blade can't cut deeper than set, preventing over-removal that would loosen the joint.

This application requires router planes with blades that can work right up to internal corners. Standard router plane blades typically work surfaces but leave small uncut areas at corners. Specialty corner blades or careful chisel work addresses these remaining spots.

The technique proves particularly useful for through-tenons that show on the opposite side of the joint. Getting both cheeks exactly parallel and at precise thickness ensures the tenon shows uniform gaps on all sides when assembled, creating clean visual lines.

Rabbet Bottom Truing

Rabbets cut for panel grooves or lid lips must have flat bottoms for components to seat properly. Hand-cut rabbets often show variations where the shoulder meets the bottom or where grain changes affected cutting. Router planes true these bottoms after the rabbet profile is established.

The router plane sole rides in the rabbet, supported by the rabbet bottom and the remaining wood ledge. The blade works perpendicular to travel direction, scraping the bottom flat. This differs from rabbet planes which cut the rabbet profile, while router planes refine existing rabbets to perfect flatness.

Through rabbets (running the full board length) clean up easily with router planes. Stopped rabbets require more care to avoid damaging the stopped end, though the controlled depth prevents cutting too deep even if you run past the stopped point slightly.

Box construction often uses rabbets to join corners. Getting these rabbet bottoms perfectly flat ensures box sides meet at precise angles without gaps. The router plane provides this flatness quickly compared to trying to achieve it through careful initial cutting alone.

Depth Control Mechanism

Most router planes use a threaded rod or knurled nut to adjust blade depth. Rotating the adjuster raises or lowers the blade in fine increments—perhaps 1/64 inch per rotation depending on thread pitch. This provides the precision control that makes router planes useful for exact depth work.

Some designs include depth stops—threaded rods that contact the plane body at set positions, providing repeatable depths for multiple identical recesses. Set the stop for hinge mortise depth and all mortises come out identical without re-measuring.

Vintage router planes sometimes use simpler clamp mechanisms where you position the blade by eye or measurement, then tighten a screw to lock it. These work but lack the precision adjustment and repeatability that threaded adjusters provide. The difference matters when cutting multiple identical recesses.

Premium router planes include depth scales marked on the adjustment mechanism. These show blade extension directly, allowing setting specific depths without trial passes. Budget versions might lack scales, requiring test cuts to establish proper depth settings.

Grain Direction Independence

Regular bench planes care deeply about grain direction because they slice along fibers. Cutting against the grain causes tearout and rough surfaces. Router planes scrape perpendicular to travel direction, meaning grain direction barely affects cutting quality. The blade encounters grain at varying angles within single passes but the scraping action handles all orientations similarly.

This grain independence makes router planes reliable in figured woods that tear out badly under regular planes. The curved, interlocked grain that causes bench plane nightmares doesn't affect router plane performance significantly. The scraping cut works regardless of fiber orientation.

The trade-off involves slower cutting speed compared to slicing actions. Scraping removes material less efficiently than slicing. But the reliability across all grain directions and the precision depth control make this slower speed acceptable for the operations router planes handle.

End grain cuts work fine with router planes despite end grain being challenging for other plane types. The scraping action across fiber ends creates clean results without the resistance and tearing that block planes working end grain must overcome through low cutting angles.

Size Range and Applications

Small router planes—perhaps 4 to 6 inches long—handle detail work in tight spaces. These work well for small inlays, narrow dadoes, and delicate joinery. The compact size allows reaching into assembled work or working small components that larger planes would overhang awkwardly.

Medium router planes at 8 to 10 inches cover general purpose applications. Hinge mortises, typical dados, and most joinery work fall into this size range. These planes provide enough mass for stable cutting without being too large to maneuver in typical furniture-scale work.

Large router planes exceeding 12 inches handle wide surface work like panel fields or large inlay areas. The extended sole provides better reference across wide surfaces. The mass helps maintain consistent cutting depth. These see less use than smaller versions because fewer operations require their capacity.

Specialized versions include corner router planes with blades mounted to cut right into corners, and old woman's tooth routers (so named for their resemblance to remaining teeth in elderly mouths) which work surface cleaning in timber framing and similar heavy work.

When Router Planes Don't Help

Initial recess cutting doesn't benefit from router planes because the blade works best refining existing recesses rather than creating them from flat surfaces. Use chisels, saws, or power routers to establish the recess rough profile, then employ router planes for final depth and flatness.

Deep recesses beyond 3/8 to 1/2 inch deep can exceed practical router plane capacity. The blade can only extend so far before becoming unstable. Very deep mortises or recesses get worked in stages—rough to depth, then router plane the bottom—or get cut entirely with other methods.

Through-width dadoes on wide panels might exceed router plane sole capacity. If the plane sole can't reach both sides of the dado simultaneously, it lacks the reference surfaces needed to maintain consistent depth across the width. These require different approaches or multiple passes with careful technique.

Angled surfaces don't suit router plane work because the sole needs flat reference surfaces to ride. Cutting recesses in curved surfaces or on angled faces requires different tools or techniques that don't depend on flat reference planes.

The Market Reality

Vintage router planes from Stanley (No. 71) or Record remain common in usable condition for $40 to $100. These tools saw regular use historically, so finding functional examples proves easier than with some specialty planes. The simple mechanism means fewer potential failure points compared to more complex plane types.

New router planes from Veritas or Lie-Nielsen cost $150 to $300 depending on size and features. These include precisely machined soles, rigid blades, and fine depth adjustments. The premium prices reflect the specialized nature and limited production volumes compared to common bench planes.

Budget new router planes exist at $40 to $80 but often suffer from thin blades that flex or sloppy depth adjustments that don't hold settings reliably. The specialized function demands precision that budget manufacturing struggles to provide consistently.

The investment in a quality router plane pays off for woodworkers doing joinery regularly. Cabinet makers hanging doors, furniture makers cutting dadoes and inlays, and anyone doing hand-cut joinery find router planes indispensable. Casual woodworkers might not encounter enough applications to justify the cost.

Sharpening Considerations

Router plane blades sharpen differently than regular plane blades because of their L-shape and scraping orientation. The cutting edge gets honed at 90 degrees to the blade shank typically, creating a square edge rather than a beveled one. Some woodworkers add a slight bevel (perhaps 5 to 10 degrees) to create a stronger edge.

The small size and odd shape make router plane blades challenging to hold during sharpening. Some woodworkers fabricate holding jigs. Others free-hand sharpen carefully. The small surface area means less material removal compared to sharpening full-size plane blades, making the process quicker despite the awkward geometry.

The sharpening angle affects cutting behavior. A 90-degree square edge scrapes aggressively but might chip in hard woods. A slight bevel reinforces the edge but reduces aggressiveness. Finding the balance depends on the woods typically worked and personal preference.

Blade condition affects router plane performance more than many realize. A dull blade compresses wood instead of cutting cleanly, leaving fuzzy surfaces requiring cleanup. Sharp blades produce smooth recess bottoms that need no further work. Regular sharpening proves as important for router planes as for any other plane type.

Router planes occupy a unique position in the hand plane family by cutting perpendicular to the sole rather than parallel to it. This geometry creates capabilities no other plane type provides—specifically, cutting flat-bottomed recesses to precise, uniform depths. The applications involve joinery refinement, inlay work, and any situation requiring exact depth control on interior surfaces. Understanding how hand planes work generally helps appreciate what makes router planes different, but the perpendicular blade orientation creates fundamentally different capabilities that make these planes essential for specific operations despite being unnecessary for others. The specialized function means router planes don't replace other plane types but rather complement them for the particular jobs where precise depth control on recessed surfaces matters.