Dado Plane

identity

• name: Dado Plane — sometimes called a housing plane (British usage, since the joint it cuts is often called a "housing joint" rather than a "dado" outside North America) [R1]. Not to be confused with the Plow Plane, its close-looking sibling optimized for the other job (see lineage), nor with the Router Plane, which trues an already-cut recess floor rather than cutting a fresh channel by itself (see how NOT to use it). A dedicated dado plane is optimized for cross-grain housings because its scoring cutters define both walls; a traditional plow plane is optimized for grooves, usually with the grain. Some dado, fillister, plow and combination designs overlap, depending on cutters, nickers, fence and guide configuration — HNT Gordon's current 1/8" dado plane is expressly described by its maker as used "across the grain or with the grain," and US136,469 claims a combined dado, plow and rabbet tool, so the contrast is one of specialization, not of mechanical prohibition [R21][R10].
• family / category: Planing tools → the joinery-cutting branch's cross-grain specialist: a bevel-down plane fitted with two scoring spurs/nickers ahead of a (usually skewed) main iron, built to cut a dado — a flat-bottomed housing channel — cleanly ACROSS the grain, where a plain iron alone would tear rather than shear the wood fiber [R2][R3].
• one-line: A narrow, fixed-width (or, on Stanley's metal No. 39 line, size-graduated-but-not-continuously-adjustable) hand plane whose two small knife-edge nickers score the cross-grain fibers on both walls of a cut a hair before the main iron lifts the chip between them, preventing the ragged tearout that cutting straight across the grain otherwise produces [R2][R4].
• not to be confused with: the Plow Plane — mechanically almost a mirror image (fenced, iron-in-body plane cutting a channel) but built for LONG-GRAIN grooving; the Plow Plane's own entry states this distinction directly from its own side and this entry confirms it independently: "a dado plane: a distinct, unfenced, fixed-width tool built specifically for cutting cleanly ACROSS the grain, which the plow plane — fundamentally a long-grain tool — is not well suited for" [cross-ref, Plow Plane, R16, HIGH]; the Router Plane (trues the FLOOR of an already-cut recess to a consistent referenced depth — it does not cut a fresh cross-grain channel, a distinction the sibling Plow Plane entry already draws from its own side and this entry's own research independently confirms) [cross-ref, R5]; the Combination Plane (Stanley 45/46/55 — absorbs the dado-cutting function among dozens of others via interchangeable cutters, a genuinely bigger and harder-to-master multi-tool, not a dado-plane substitute for a beginner) [cross-ref, R6]; and the Rabbet Plane's own No. 239 listing, which this entry's research indicates is misfiled — see lineage [R7].

✦ how NOT to use it

• not-for (jobs it should never do):
  • not the natural choice for the Plow Plane's long-grain grooving work — a fenced plow with a matching cutter is usually the better specialist, though some dado, fillister, plow and combination designs overlap and a dado plane can cut with the grain on models whose maker says so — see matching [cross-ref].
  • not a one-tool equivalent to the Router Plane's recess-floor-truing work — see matching [cross-ref].
• dangerous (misuse that injures the user). No dado-plane-specific injury-frequency evidence was located in this run's searching. That is a research result, not a risk assessment — the tool has exposed sharp nickers and a sharp skew iron, a backward scoring stroke, antique wedges/spurs/stops that can be loose or damaged, a body that can bind or leave the work, and force applied toward an exit edge. The controls below are the ones the hazards themselves call for, and they follow CCOHS's general sharp-edge and chisel guidance rather than a generic power-tool caution [R26][R27].
  • using the plane without first inspecting it — check the body for cracks and bow, and check cutter retention, both nickers, the wedge or lever cap, the depth stop and the guide before each session. A cracked, loose or incomplete plane comes out of service until repaired; this matters most on antiques, where Leach's own handling record names broken spurs, snapped lever caps and stripped depth-stop threads as common [R17][R26].
  • holding the stock or the batten by hand instead of securing it mechanically — clamp both. Never let a hand sit in the plane's possible slip path, and keep hands behind the active scoring and cutting edges [R26].
  • standing or reaching past the exit edge — plan the exit stroke so that the loss of resistance at breakout does not throw you off balance, and keep your body out of the plane's projected path [R26].
  • setting the iron or the nickers deep to work faster — excessive projection raises the force needed, and with it the wandering, the tearout and the chance of losing control. Set both shallow and take more passes.
  • forcing a plane that binds, chatters, or whose cutter has shifted — stop. A geometry or workholding fault is not something to overcome with more force; re-seat, re-inspect, and re-clamp instead.
  • treating a removed nicker or skew iron as a loose part — they are exposed sharp edges. Sharpen, carry and store them as such [R26].
  • grinding a nicker, skew iron or casting without eye and dust controls — any grinding or powered reshaping (regrinding an iron, re-profiling a spur, or the casting-narrowing the No. 39 collector record describes) throws particles and fine dust: wear eye protection, use the grinder's own guard and tool rest per its manufacturer's instructions, and control the dust. A hand-sharpening stone carries no such hazard; the grinder does (the reviewer's 2026-08-01 fix 1).
  • forgetting that the knife and chisel steps carry their own risk — pre-scoring the walls with a marking knife and undercutting the exit line with a chisel are part of this procedure, and the relevant cutting-tool controls apply to them: clamp the stock, keep your balance, cut away from the body, keep the holding hand behind the edge [R27].
  • assuming the powered substitutes are safer because they are modern — a router or a table-saw dado stack has its own manufacturer instructions, guarding, workholding, feed-direction, dust, hearing and eye-protection rules. Nothing in this hand-tool entry transfers to them.
• damaging (misuse that ruins the tool or the work):
  • skipping the pre-scoring/nicker step, or forcing the cut without establishing the boundary lines first, causing catastrophic tearout — confirmed independently across every history and technique source above (Rozaieski, Cohen, the No. 39's own two-spur design) [R8][R13].
  • letting the nickers dull or go out of alignment relative to the main iron — the nickers do delicate, precision scoring work in front of the main cutter and must be kept sharper and correctly proportioned (wider than the iron, which is wider than the body) or the entire cut degrades into tearout: "If the edge of the cutter is outside the line being cut by the spur, you will get tear-out" [R14][R20, HIGH].
  • a warped or unflat plane body/sole causing a documented "skip and dig" fault — a named, extended forum troubleshooting thread diagnoses this fault directly to sole/body flatness, not iron sharpness: "there is a good chance that your vintage wooden dado plane has a warped body. If so, it will not plane straight" (Derek Cohen); "The symptoms you describe are from the sole not being flat or the iron not bedded" (Matthew Bickford, the same named professional moulding-plane maker already cross-referenced in the sibling Moulding Plane entry) [R20, HIGH — full thread read].
  • cutter overlapping the nickers, vertically or horizontally, causing chatter and tearout — a specific, named, correctable setup fault: "Cutter's edges should be flush with the outside edges of the skates" [R20, HIGH].
• beginner-trap (mistakes that look fine until they aren't):
  • not registering the plane against a batten/fence for the first passes and wandering off-line — the single most repeated beginner failure across every forum source consulted: "A plane like this with three cutting edges will try to follow grain, along a path with least resistance... I'm forever digging in on one side, or the other" [R20, HIGH].
  • setting the nickers to score too deeply, "hoping to finish faster" — Frederick Skelly's own documented first-timer mistake: "If you try to score too deeply, your cuts will be very ragged and ugly. Then you will drive yourself bonkers trying to find a way to sharpen the nickers more than they really need to be" [R16, HIGH].
  • not drawing the plane backward before the first forward pass to establish the nicker's scoring line — a specific, non-obvious first step multiple named forum posters had to be told rather than discovering on their own [R16, HIGH].
  • setting the depth stop wrong and cutting through a thin panel — not directly sourced to a named account this run despite being a mechanically obvious risk given every source's emphasis on depth-stop precision; flagged here as a reasoned extension rather than a directly cited failure [R25, reasoned extension].
• lineage-misuse (treating it like a related-but-different tool):
  • expecting a plow plane or combination plane set up for grooving to perform as well as a dedicated dado plane, or vice versa — the sibling Combination Plane entry already documents Warren Mickley's own account of using a Stanley 45 for "most dadoes" while candidly noting it has "more set up time" than a dedicated tool [cross-ref, Combination Plane]; confirmed directly here by the same named source in a dado-specific thread [R18, HIGH].
  • treating the nickers as optional or fully interchangeable with a knife-scored line, or vice versa — a real, unresolved craft disagreement preserved rather than flattened: Warren Mickley uses the nickers alone and explicitly does not pre-score with a knife on a dedicated dado/combination plane, while Derek Cohen's own corrected practice favors knife-scoring first, having found nicker-only registration unreliable in his own use [R18][R13, both HIGH].
  • expecting the No. 239/239½'s narrow width family to substitute for a true adjustable plow/groove plane, or vice versa — confirmed by the No. 239/239½'s own internal history: Stanley's engineers had to explicitly redesign the 239½ variant (dropping the spur cutter) specifically because the standard dado-plane geometry doesn't serve long-grain plowing well without modification, then had to re-add a fence to the base No. 239 in 1925 once a single tool needed to do both jobs [R7, HIGH].

correct use

Brief — the workbench holds deep operation. In one sentence: score the boundary lines, register the plane against a batten or fence, and let the nickers sever the cross-grain fibers a hair ahead of the main iron on every pass.

• what it's genuinely good at: cutting a clean, flat-bottomed, square-walled housing channel across the grain in one tool, without the tearout a plain iron produces cutting cross-grain — and, per a named source, forming the basis of a sliding-dovetail housing when one or both walls are angled [R13, HIGH].
• how to use it well (brief), per a named, credentialed source's own corrected practice (he states what he used to do and why he changed): lay out the boundary lines with a square, then pre-score them with a marking knife in several light-to-firm passes for a clean, straight line — Derek Cohen states directly that relying on the plane's own nickers alone to establish the line by dragging the plane backward over the work is unreliable, since "it is very easy for the nickers to be carried off line by the grain... the result is a mish-mash of lines" [R13, HIGH]. Undercut the exit-side boundary line with a chisel first to prevent spelching (exit-side tearout); set the fence or batten against one scored line and the depth stop to the target depth; take the first shaving light, working from the far end back toward the near end; keep the body pressed firmly against the fence/batten throughout and don't lift the plane between passes; once the housing is a few passes deep (roughly 1/8"), the fence/batten can be removed since the plane now registers within the cut itself; finish keeping the plane vertical — balanced on two skates, easy to lean without noticing — until the depth stop bottoms out [R13, HIGH — full sequence read directly].
• an honest, real, unresolved disagreement on the pre-scoring step itself, worth preserving rather than flattening. Warren Mickley states plainly he does not pre-score at all when using a dedicated dado or combination plane: "I do not use a knife to score dados that are to be cut with a dado or combination plane. That is what the nickers are for" [R18, HIGH]. This sits against Cohen's own corrected practice above, which favors knife-scoring precisely because nicker-only scoring proved unreliable in his own experience. Both are legitimate, technique-dependent positions from named, experienced practitioners, not a settled single answer.

✦ matching

The workbench's first read.

• does: cuts a flat-bottomed, square-walled channel/groove across the grain — a dado — sourced directly and matching this corpus's Plow Plane entry's own framing from the opposite side: "A dado is, by definition, cross-grain and requires a method to score the wood to prevent tear-out" [R12, MEDIUM]; a second named source states the mechanical reason plainly: "The plow plane has no spurs to allow cutting across the grain... Enter the dado planes" [R23, HIGH — full text read]. Also forms the basis of a sliding dovetail when one or both walls are cut at an angle [R13].
• suits: repeated cross-grain housings of a width matching the plane — shelf and case housing joints (the classic bookcase-shelf application, per the Sawmill Creek bookcase-building thread cited above); sliding-dovetail housings; work where quiet hand cutting and a reliable depth stop are worth having. Width matching is literal: a fixed-width plane must match the actual mating stock, or be used as part of a controlled widening method — nominal lumber thickness is not enough. Note: this entry could not directly source stair-stringer housed joints or breadboard-end housings tied to this specific plane by name, despite these being standard dado-joint applications generically — flagged as an honest gap rather than asserted [R18, honest gap].
• kit-fit:
  • pairs with: a marking knife/square, for pre-scoring the boundary lines before the first pass (Cohen's own corrected practice) [R13, HIGH]; a clamped batten/straightedge as the fence substitute on the unfenced traditional wooden plane and the No. 39 line, both of which have no integral fence [R13][R20, HIGH]; a chisel, for undercutting the exit-side line to prevent spelching; and, afterward, a Router Plane, for truing/deepening an already-cut dado's floor to a consistent depth [R5, HIGH].
  • substitutes for / is substituted by: a router + straightedge jig, or a table-saw dado stack, are the standard modern methods for the identical cut [R11, MEDIUM]. A Router Plane is not a one-tool equivalent to a dedicated dado plane, but it is an effective finishing and depth-control tool in the common saw-and-chisel dado method — knife or saw the walls, clear the bulk waste with saw and chisel, then bring the floor to depth with the router plane. Fine Woodworking presents exactly that as a slower hand-tool way to make a dado, and Popular Woodworking describes the same saw/chisel/router-plane construction; it is a lower-cost kit path, not a non-option [R8][R28]. What the router plane will not do alone is remove a full untouched channel: "router planes really are not very good at making their own channels... they clean up the aggressive cuts made by rabbet, dado, grooving or plow planes" [R5, HIGH — the same named source, Shannon Rogers, already anchoring this exact distinction from the Plow Plane entry's own side, independently corroborated here applied to this tool specifically]. A Plow Plane or Combination Plane set up for grooving is a real but imperfect substitute — Warren Mickley uses a Stanley 45 for "most dadoes" despite candidly noting it "has more set up time" than a dedicated tool [cross-ref, Combination Plane, R18, HIGH].
  • does not replace: the Plow Plane's specialism in cutting a groove WITH the grain — on most dedicated dado planes the nickers do no useful work in long grain and add friction, wear and clogging where no cross-fiber severing is needed, so a fenced plow with a matching cutter is normally the better tool. This is a default-role distinction, not a prohibition: nicker retraction and model geometry decide it, and some makers rate their own dado planes for both directions [cross-ref, Plow Plane, R16][R21]. Also does not replace the Router Plane's job of truing an already-cut recess floor to a consistent referenced depth [cross-ref, R5, HIGH].
• not-for (project-keyed):
  • conditional, not excluded — a long-grain groove. Mechanically possible on some models, but a plow plane with a fence and a matching cutter is usually the more natural choice. Check the particular plane's nicker setup and fence before deciding [R21][R16].
  • don't reach for it to true or clean up a dado someone else already cut — that's the Router Plane's job [cross-ref, R5].
  • stopped housings are not through dados. A stopped housing's longitudinal endpoint has to be laid out and approached with a stopped-cut method; neither the depth stop nor a side guide defines that endpoint. Plan it before the first pass.
  • "drawer-bottom grooves" belong here only when the drawer member and grain direction are named — depending on the component they run both along and across the grain, so the generic phrasing has been removed rather than left to mislead the match.
  • don't expect a plain unfenced traditional dado plane or a No. 39 to deliver the Combination Plane's dozens of other joinery cuts — a dado plane cuts dados (and, with a fenced variant like the No. 239½, a narrow long-grain groove); it does not do rabbets, beads, or mouldings [cross-ref, Combination Plane, R6].
• access: genuinely two-sided, without a single dedicated named "access" essay for this tool the way the sibling Plow Plane entry found for its own tool — flagged honestly rather than papered over with an inference. What IS directly sourced: Derek Cohen's own comparative test found a dedicated modern dado plane (HNT Gordon) the easiest to set up and use of three options tested, ranking it ahead of both the Veritas Combination Plane and the Stanley No. 46 on ease of nicker alignment — "Ease of use and set up goes to the HNT Gordon... It cut with less attention needed for accuracy than the others" [R13, HIGH], supporting a genuine "fewer moving parts than a combination plane" access claim from a named source who tested all three side by side. Against that, the batten/fence-registration requirement and the pre-scoring-technique disagreement (see correct use) are a real, documented harder-than-it-looks caution, borne out directly by the Skelly tuning-diary thread's own first-timer struggles [R16, HIGH].
• revival: the strongest sourced argument found is efficiency for a project with several repeated dados, not a quietness/aesthetic framing: "When a piece requires a dado, there tend to be several, and in these situations, the most efficient method is a sharp, tuned dado plane" [R5, MEDIUM]. A targeted search for a quietness/tactile/traditional-technique revival argument — parallel to what the sibling Plow Plane entry found via Lee Valley's own "quieter alternative to a router" marketing copy — did NOT find an equivalent named claim for the dado plane specifically; reported as an honest gap rather than invented [R24, honest gap].

anatomy

• the body/stock — traditional wooden examples are beech, consistent with the general old-plane-stock convention this corpus's other joinery-plane entries document; not independently re-sourced for this tool specifically this run, held as a reasoned inference from the family rather than a direct citation [R19, MEDIUM — inference].
• the main cutting iron — set at a skew running the full width of the sole on most true dado planes; two features together define the tool: "a skewed iron that extends all the way across the sole" plus the paired-spur iron ahead of it [R12, MEDIUM].
• the nickers/spurs — two small, hardened, knife-edge scoring cutters, one on each side of the cut, set to score the cross-grain fibers on both walls of the dado a hair before the main iron lifts the chip between them. The functional rule is that the scored walls, the cutter projection, the skates and the body clearance must all agree — so the body does not bind in the channel, and the cutter does not break fibers beyond the scored lines. On many antique wooden planes that is achieved by nickers slightly wider than the iron and an iron slightly wider than the body, but this is model-specific geometry, not a universal: HNT Gordon lists its current 1/8" plane with a nominal 1/8" main blade and a nominal 1/8" nicker blade, so "never equal" does not hold across the class [R21]. Use the maker's own instructions, or measure the particular plane, before filing any hardened cutter or nicker — this is setup-critical, and applying one plane's geometry to another is how good irons get destroyed. Warren Mickley's advice below is strong practitioner evidence for the antique wooden planes he works, and should be read that way rather than as a class-wide law: "The nickers have to be wider than the cutting iron. If they are very close to the same width, the alignment has to be perfect to avoid trouble. The nickers also have to be wider than the body of the plane... You should not narrow the nicker blade unless you would consider narrowing the stock of the plane also" [R14, HIGH — full text read]. A second named poster, working a different geometry detail: the spurs "have a round edge, with the roundness facing to the bottom. File the spurs from the inside, leave the outside straight" [R20, HIGH — full thread read].
• the depth stop, and the three axes it is routinely confused with. Keep these separate, because blending them is how a stopped housing gets overrun:
  • depth — the depth stop, and nothing else, limits how deep the floor goes. On the metal No. 39 line it is screw-adjustable; on old single-width wooden examples it may be fixed or independently adjustable depending on how the stop is built into the stock, so "adjustable stop" and "fixed stop" describe constructions, not eras [R12][R9].
  • lateral registration — a fence, a clamped batten, or (after the first few passes) the established channel itself controls the line of the cut. It has nothing to do with depth.
  • longitudinal start and stop — where a stopped dado begins and ends is laid out on the work and approached with a stopped-cut method. Neither the depth stop nor a side guide defines that endpoint.
• the skate — the sole strip(s) directly supporting the cutter's edges; a "central skate and a width stamp on the toe or heel" is how one source identifies a true dado plane at a glance, distinguishing it from a plow plane's different sole geometry [R12, MEDIUM].
• the fence — present on adjustable/metal forms in the Stanley No. 239 line (see lineage) but absent on both the traditional single-width wooden plane and the graduated-but-fixed-width Stanley No. 39 series, both of which are instead guided by a clamped or nailed wooden batten — directly confirmed: "The dado plane is used in conjunction with a shop made straight edge" [R13, HIGH — full text read]; multiple named forum posters independently corroborate the same batten-dependent practice for the No. 39 line specifically: "I can't cut straight without a batten, either"; "I use a batten now, and just nail it on" [R20, HIGH].
• named part-failure patterns — Patrick Leach's collector reference names, from direct handling of many examples: broken/missing spurs, snapped lever caps, stripped depth-stop threads, and a genuinely specific parts-interchangeability caution: spurs are not interchangeable between earlier and later No. 39-line planes (earlier examples are narrower, with correspondingly sized slots), and most spurs are size-specific except the flat right-hand spur, salvageable across sizes since every plane in the series is machined flat on that side [R17, HIGH — full text read].
• modern-maker anatomy (HNT Gordon, as listed 2026-08-01 — dimensions vary by model, and maker listings decay, so this is dated rather than stated as standing fact). Gidgee body with a brass wedge mechanism, a 60° bed angle with a 20°-skewed 3/16"-thick tool-steel blade (Rc 62–64), plus a separate HSS nicker blade with mechanically adjustable nicker depth and a mechanically adjustable depth stop. Four widths listed, not three: 1/8", 1/4", 1/2" and 3/4". Bodies are 230mm × 75mm with the width varying by model — the 1/8" plane is 230 × 22 × 75 mm, not the 28 mm quoted for the wider models — and the 1/8" was listed at AUD 718 with a stated 1–2 week wait. The maker's own description says this plane is used "across the grain or with the grain," which is why the long-grain prohibition was removed above [R21, manufacturer product page, checked 2026-08-01].

variations (living)

• Traditional fixed-width wooden dado plane — one specific width per plane, no fence, guided by a clamped batten/straightedge; historically sold and owned in small numbers rather than full graduated sets, per the period cost/ownership finding above [R8, HIGH]. Benjamin Seaton's 1796/97 cabinetmaker's tool chest (the most complete surviving 18th-century British cabinetmaker's kit, now documented via Jane Rees's standard reference work) contained dado planes in five documented widths — 3/8", 1/2", 5/8", 3/4", and 7/8" — among its 76 planes [R22, HIGH — museum/archival reference, see proof of existence].
• Stanley No. 39 metal dado-plane series (1900/02–1953) — skew-ironed, spurred, adjustable depth stop, no integral fence (batten-guided); sold across eight graduated fixed widths: 1/4", 3/8", 1/2", 5/8", 3/4", 13/16", 7/8", and 1". The 13/16" size is a genuine rarity, made by grinding a 7/8" casting narrower with the "7/8" marking ground off before japanning — flagged by the collector-standard source as one of the rarest Stanley planes and a known target for modern fakes [R17, HIGH — full text read]. Production-year ranges vary slightly by size across sources (roughly 1900–1935 for the 7/8" size up to 1900–1953 for the 1/2") [R9, MEDIUM-HIGH — cross-checked across two independent collector-reference sources].
• Stanley No. 239 / No. 239½ (1915–1929) — a narrower, later addition to the No. 39 family (see lineage and history for the full internal redesign account); extended the dado-plane width range down to 1/8", and briefly (1919–1923, as the "No. 239½") existed as a spur-less, fenced variant intended only for long-grain grooving despite the name [R7, HIGH — full text read].
• Stanley No. 46/47 skew combination planes — absorbs dado-cutting via the redesigned Dorn/Traut mechanism described in lineage; already documented in the sibling Plow Plane entry's own production table; not re-derived here [cross-ref, R10].
• Combination-tool absorption more broadly (Stanley No. 45/55) — cuts dados among dozens of other functions via interchangeable cutters; already fully documented in the sibling Combination Plane entry, including its own quoted 1898 catalog line naming "dado plane" as one replaced function [cross-ref, Combination Plane, R6].
• Modern replacement methods — a router with a straightedge/edge-guide jig, or a table-saw dado stack, are the standard tools used for this cut in most shops today; these are the tool's functional descendants/replacements, not variations of the same tool, and are treated that way in this entry's matching block [R11, MEDIUM].

trades (where it appears, with trade-specific notes)

• woodworking / cabinetmaking (primary trade) — shelf and case housing joints, drawer-bottom grooves, sliding-dovetail housings. Fully documented above [R8][R13].
• timber framing / other trades — no source located placing the dado plane specifically in timber framing, stair-building, or non-woodworking trades in this run's research, despite housed stringer joints being a classic stair-building application generically; held as an honest, unconfirmed gap rather than asserted [R18, honest gap].

lineage

• ancestors:
  • No single earlier tool is separately documented as the dado plane's direct wooden ancestor — like the Moulding Plane and Plow Plane, it belongs to the broad family of fenced/bodied joiner's planes that had reached a recognizably modern wooden form by the 18th century, though the specific fixed-nicker-and-depth-stop design "wasn't common until the early 19th [century]" per a named period-technique source [R8, HIGH].
• descendants / living variants:
  • Stanley's No. 39 metal dado-plane line (1900/02–1953) — the tool's own most complete metal-bodied realization, produced across eight graduated fixed widths from 1/4" to 1" [R9, HIGH — read in full].
  • Stanley No. 46/47 skew combination planes — this entry's own patent research (below) traces these directly to a redesign of an earlier dado-plane mechanism, making the combination plane's dado function a genuine descendant of this tool's own patent lineage, not a parallel independent invention [R10, HIGH — patents read in full].
  • The modern functional replacement: a router with a straightedge/edge-guide jig, or a table-saw dado stack — the standard methods used for this exact cut in most shops today [R11, MEDIUM — the substitution is well-attested across multiple sources, though no single named source states the displacement in so many words, and no measured share of shops was found; the earlier "nearly every shop" was unmeasured and has been withdrawn].
• contemporaries — related but genuinely different tools:
  • The Plow Plane — cuts a groove down the field or along an edge WITH the grain; this entry's sibling names the dado plane directly as its own cross-grain counterpart in five separate passages, and this entry confirms the relationship from its own side [cross-ref, Plow Plane, R16, HIGH].
  • The Router Plane — trues the floor of a recess ALREADY cut to a consistent depth referenced off the face of the work; a named source (Shannon Rogers, The Renaissance Woodworker — already a recurring cross-corpus voice in this corpus's Plow Plane and Shoulder Plane entries) states this directly of the dado plane specifically: router planes "really are not very good at making their own channels... they clean up the aggressive cuts made by rabbet, dado, grooving or plow planes" [R5, HIGH — full text read].
  • The Combination Plane (Stanley 45/46/55) — absorbs dado-cutting among dozens of other operations via interchangeable cutters; the sibling entry already quotes an 1898 Stanley catalog naming "dado plane" as one function a No. 55 replaces [cross-ref, Combination Plane, R6, HIGH].
  • The Rabbet Plane's No. 239 — this entry's own research resolves an open cross-reference question. The Rabbet Plane entry (Run 331) lists Stanley's No. 239 under its own numbered rabbet-plane production table as "dado plane with spurs and depth stop, 1916–1942." A directly-read, named collector-history source states plainly that Stanley's own 1915 catalog placed the No. 239 "in the same group with the No. 39 series of Iron Dado Planes" — i.e., as a member of THIS tool's family, not the rabbet-plane line [R7, HIGH — full text read]. This entry flags the correction rather than silently re-filing it; see open gaps.

Petroski lens — the patent-to-patent redesign chain, this entry's first organizing finding. No source found in this run's research explicitly invokes Petroski's "form follows failure" language for the dado plane by name — an honest gap consistent with the pattern the sibling Plow Plane, Rabbet Plane, Moulding Plane, and Combination Plane entries each report for their own tools. What IS directly and unusually well documented: a genuine patent-to-patent mechanical lineage, traced here across six separate documents and six named inventors — Rice, Dorn, Traut, Miller, Bailey and Bodmer, with Traut appearing twice. (The earlier "five records / five inventors" phrasing was an arithmetic error against this entry's own list and has been corrected; each document is now cited by its formal patent title, because a database's functional category label is not the document's title.) Royal B. Rice patented a removable scoring coulter in 1869 — US 98,108, formally titled Improvement in Carpenters' Plow, whose specification calls its subject a matching plane and claims a removable coulter with lips ahead of the bit. It is real and relevant prior scoring-cutter evidence, and a precursor — not formally a dado-plane patent, and not the earliest dado-plane-specific patent, which is what this entry previously called it under the invented title "Knickers for Dado Plane." That claim is withdrawn. US 129,010 is the earliest specifically titled dado-plane patent established in this review, unless an earlier primary document turns up. Rufus H. Dorn patented that complete dado plane in 1872 (US 129,010, Improvement in Dado-Planes) built around a pivoting, angle-adjustable cutting blade paired with a laterally-adjustable spur that had to track the blade's swing angle — a genuinely clever but mechanically complex answer to the problem of cutting different widths without swapping irons. Justus A. Traut then patented, in 1873 — US 136,469, formally titled Improvement in Carpenters' Planes, and describing a combined dado, plow and rabbet plane — what DATAMP's own cataloguing calls directly "Traut's redesign of the Dorn patent dado plane [129,010]... functionally superior to the swing-arm design" — and this redesigned mechanism became the basis for the Stanley No. 46 and No. 47 skew combination planes, already documented in the sibling Plow Plane entry's own production table. This is a rare case in this corpus where the failure-to-fix relationship between two inventors' work is stated directly by a cataloguing authority, not inferred by the entry-writer — one tool's whole mechanism exists because a named engineer looked at a named predecessor's design and judged it needlessly complex [R10, HIGH — three patents read/verified directly on DATAMP and Google Patents].

history

• origin — genuinely old, with an honest gap on the earliest specific form. Wooden dado planes date to the 18th century in general form, but "the wooden form we know today [fixed depth stop, two spurs, skewed iron] wasn't common until the early 19th [century]," per a named, published woodworking-magazine source [R8, HIGH — full article read]. Requested named 18th-century makers (Robert Wooding, I. Walker) were searched for specifically and not confirmed as dado-plane makers by name in this run's research — an honest gap, not fabricated.
• the mechanism's stated purpose, sourced directly and independently confirmed across multiple voices. A dado is, by definition, cut across the grain, and cutting straight across the grain with a plain iron lifts a chip whose leading edge is unsevered fiber, which tears rather than shears cleanly: "A dado is, by definition, cross-grain and requires a method to score the wood to prevent tear-out" [R12, MEDIUM]. A named, frequently-cited reviewer states the failure mode from direct experience: "Without aligned and sharp nickers, since you are planing across the grain, the wood will tear out and leave a ghastly mess" [R13, HIGH — full article read].
• a real, named period technique detail on width and ownership economics. Bob Rozaieski, writing in Fine Woodworking, states dado planes historically ranged "typically 1/4 in. to 1 in. wide, in 1/8-in. increments, with many manufacturers also making a 13/16-in. size to match a common stock thickness" — and adds a genuine cost/ownership finding: dado planes were "quite complex" relative to other wooden planes, "up to two times more expensive," so "it was unlikely that most joiners and cabinetmakers of the time would have owned an entire set of dado planes. Instead, they may have made do with two or three" [R8, HIGH — full article read]. Warren Mickley, a named and frequently-cited Sawmill Creek authority (already a recurring voice in the sibling Rabbet Plane and Combination Plane entries), independently corroborates from a primary period source — Peter Nicholson, writing in 1812 — that dado planes were "typically 3/8 inch wide," and adds a real period workaround technique this narrower standard width implies: joiners made two overlapping passes with one narrow plane plus a chisel-cleared middle strip to cut a wider dado than any single plane's fixed width, rather than owning a plane for every width [R14, HIGH — full forum posts read].
• a named 19th-century American maker, with a genuinely unusual institutional origin. Casey, Kitchel & Co. (Auburn, NY), trading 1847–1856/58, made rabbet, dado, and moulding planes; surviving 3/4" and 7/8" examples are documented on collector sites. The firm's own roots trace to 1823, when Truman McMaster and Nathaniel Garrow began a plane-making operation inside the Auburn State Penitentiary, using convict labor — later incorporated as the Auburn Tool Company (1864), the same maker already documented in the sibling Moulding Plane entry (35,000 planes/year by 1865, merged into Ohio Tool Co. in 1893) [R15, MEDIUM — collector/retail synthesis, not independently fetched to a primary company ledger this run].
• the founding metal patent, verified directly on DATAMP. US Patent 706,704 — formally titled Plane, catalogued by DATAMP in its dado-plane product family — inventor Justus A. Traut, New Britain, CT, granted August 12, 1902, assigned to the Stanley Rule & Level Co. — DATAMP's own cataloguing states directly this is the base patent for the "Stanley #39 family of metallic dado planes," matching the No. 39 line's own confirmed 1900/02 production start [R10, HIGH — DATAMP record fetched directly].
• the No. 239's own founding patent, and its own internal redesign history — resolves an open question and corrects a sibling entry's placement. US Patent 1,134,072 — formally titled Plane, its specification expressly describing a plane intended to score ahead of the cutter — inventor Christian Bodmer, New Britain, CT, granted March 30, 1915, assigned to Stanley Rule & Level Co. — DATAMP's cataloguing states directly this underlies the "Stanley #239 family of dado planes" [R10, HIGH — DATAMP record fetched directly]. A directly-read, named collector-history source adds real internal product history: the No. 239 is a narrow 1/8"-wide plow/dado cutter (grooves to 1/2" deep) with a depth stop and a vertical double-spur cutter, extending the No. 39 family's width range down below its own 1/4" floor. A separate, short-lived variant — the No. 239 1/2 "Improved Dado Plane" (1919–1923, only four years in production) — dropped the spur cutter entirely and added a full-length fence, intended only for grooves running WITH the grain (functioning as a narrow plow, not a dado plane at all, despite carrying the name) — an omission the source states was not disclosed in period Stanley catalogs. In 1925 Stanley added a fence back onto the standard No. 239 itself (making it usable both across AND with the grain), and by 1926–29 it was offered in 1/8", 3/16", 1/4", and (from 1929) 5/32" widths [R7, HIGH — full article read]. Bodmer himself is confirmed here as a real, DATAMP-verified Stanley patentee active in exactly this plane-family space in the 1910s — a figure the sibling Rabbet Plane entry had separately flagged as an unverified name behind a different (1910) patent pair; this run confirms Bodmer's activity in the adjacent 1915 dado-plane patent without resolving that separate, earlier unverified claim.
• two further, less commercially significant American patents, verified at bibliographic depth on DATAMP: US Patent 165,356, formally titled Improvement in Dado-Planes — inventors Charles G. Miller and Leonard Bailey (both New Britain, CT), granted July 6, 1875, assigned to Leonard Bailey — a genuinely notable co-patentee, since Bailey is the same inventor behind the Bailey bench-plane mechanism underlying most Stanley bench planes to this day [R10, HIGH]. US Patent 897,556 (M.A. Clark, 1908) and US Patent 984,610 (H. Smiley, 1911) are both listed under DATAMP's dado-plane patent category but were not independently fetched and read in full this run — an honest gap, not asserted as commercially significant without further reading [R10, MEDIUM — listed, not read in full].
• modern context — largely ceded to power tools, but not stated as an explicit displacement narrative by any single named source. No source found this run states in so many words that dado planes have been "replaced" by routers or table saws — the substitution is functionally well-attested (see matching), but the entry declines to assert a stronger displacement claim than its sources actually make [R11, honest gap].

✦ human side

• a real, named, real-time forum tuning diary — the strongest human-side material found for this tool. Frederick Skelly (Sawmill Creek, 2015) documented, across a multi-day thread, restoring a $15 antique-store wooden dado plane from scratch, coached in real time by four named experts (Darrell LaRue, Jim Matthews, Derek Cohen, Warren Mickley). His own closing "Newbie Notes" are a genuine first-person account of what actually goes wrong learning this tool: the nickers cut on the pull (backward) stroke, not the push; drawing the plane backward before the first forward pass is "a must"; and scoring too deep "hoping to finish faster" backfires directly — "you will drive yourself bonkers... and use up 1/4" of your 150 yr old plane's nicker and be very very embarrassed. DAMHIKT [don't ask me how I know this]." His closing verdict, after the tuning succeeded: "A well adjusted dado plane is a lovely tool to use. Nice, smooth sides and bottom. Well worth the $15 I paid" [R16, HIGH — full thread read, five named participants].
• a named, credentialed reviewer's direct, less favorable verdict on the metal Stanley No. 39 line — presented honestly rather than smoothed toward consensus. Patrick Leach, the canonical Stanley collector-authority already cited HIGH by three sibling entries (Plow Plane, Rabbet Plane, Combination Plane), states plainly of the No. 39 series: "I don't like these planes at all" — not for being metal generally, but specifically because "there simply isn't a nice surface for your forward hand. Instead, the metal depth adjustment screw, as well as the tops of the spurs, stick up from the top of the plane, which physically hurts your hand... they're downright bloody when using them on hardwoods" [R17, HIGH — full text read]. He also gives a real period buying-economics comparison: needing several widths made the No. 46 combination plane the more economical purchase overall, while a single fixed width made a single No. 39 the better buy [R17].
• a genuine, unresolved disagreement between two credentialed practitioners on bed-angle theory versus observed practice. Warren Mickley, reviewing a modern HNT Gordon dado plane's 60° bed specifically for cross-grain cutting: "I looked at the HTN Gordon plane. It has a 60 degree bed, which is nuts for crossgrain work." Derek Cohen — the same named reviewer whose head-to-head test anchors much of this entry's technique and matching material — concedes the theoretical objection directly but reports the opposite in practice: "all commonsense says that these planes will struggle to work. Yet they perform amazingly well." Neither source resolves the tension; it is preserved here as a real, live disagreement between two named, experienced voices rather than flattened to one verdict [R18, HIGH — full thread read].
• a named, dated, documented head-to-head test — the entry's second-richest source. Derek Cohen, a frequently-published named reviewer already cited across this corpus's joinery-plane entries, tested a vintage dado plane (which he reports performed "very poorly indeed" for years due to misaligned nickers), a router-jig method (effective but noisy), a Stanley No. 46 combination plane, the Veritas Combination Plane, and a modern HNT Gordon dedicated dado plane against each other for cutting the same housing joints. His documented verdict favored the dedicated modern tool decisively: "a clean dado with vertical sides and smooth floor... Even the ends of the dado do not reveal any spelching [exit-side tearout]. This is a better result than achieved by the power router... I cannot see why one would want to made through dados any other way" [R13, HIGH — full article read].
• a live, named debate on dedicated vs. combination-plane dado work, corroborated across a full forum thread. Sawmill Creek (2022): Warren Mickley states he "use[s] a Stanley 45 plane for most dadoes" despite owning theoretical dedicated alternatives, candidly noting it "can be adjusted to make dadoes up to 1/16 wider than the cutter width... Compared to a dedicated dado plane it has more set up time." Mark Rainey, independently, reports trying a Stanley 46 but never getting it "tuned up to my exacting standards," compared to an HNT Gordon dedicated dado plane described as "a sweet experience." Jason Buresh, a named poster, supplies the honest volume-work counter-argument this corpus has now seen in several sibling entries: "If you truly have to cut that many dados that you are considering buying a dedicated plane, then may I suggest using a router or a table saw with a dado stack... Don't be under the illusion that you can just buy a vintage 39 and start cutting perfect dados" [R18, HIGH — full thread read]. The thread's own live occasion — a woodworker weighing tool options for building bookcases to house roughly 4,000 books — is a genuine, concrete, named use-case discussion, not an abstract debate [R18].
• injury/damage accounts — an honest, near-total gap, consistent with the pattern this corpus's other joinery-plane entries report for their own tools. A targeted search for dado-plane-specific injury accounts found none. Reported honestly as an unfilled gap, not a confirmed absence — and not a finding that the tool is safe: the hazard class is built from the tool's own mechanism under how NOT to use it — dangerous.

✦ proof of existence

• the Seaton chest (1796/97) — Benjamin Seaton's cabinetmaker's tool chest, described in the standard reference (Jane Rees) as "the finest and most complete surviving example of an 18th century cabinet-makers kit in Britain, if not the world," supplied by Christopher Gabriel and Sons of London, contained dado planes in five documented widths (3/8", 1/2", 5/8", 3/4", 7/8") among its 76 planes — a dated, physically-surviving, well-documented set, catalogued via the Smithsonian Institution library's own reference record for Rees's book [R22, HIGH — museum/archival library reference].
• Smithsonian, National Museum of American History — a dado plane is catalogued directly: ID Number MC.260301.055, Accession Number 260301, Catalog Number 260301.055, materials listed as metal (brass and steel) and wood (beechwood). The object page itself would not render on direct fetch (likely JS-gated, a pattern this corpus's sibling entries have hit on other collector/museum sites); the accession data above comes from an indexed search snippet, not a directly-rendered page, so this is held at MEDIUM-HIGH rather than fully independently verified [R26, MEDIUM-HIGH].
• the founding metal patent, verified directly on DATAMP: US Patent 706,704 — formally titled Plane, catalogued by DATAMP in its dado-plane product family — Justus A. Traut, granted August 12, 1902, assigned to Stanley Rule & Level Co. — the base patent for the Stanley No. 39 family [R10, HIGH — DATAMP record fetched directly].
• an early scoring-coulter precursor, corrected: US Patent 98,108, formally titled Improvement in Carpenters' Plow, Royal B. Rice, Williamsburg, MA, granted December 21, 1869 — its specification calls the subject a matching plane and claims a removable coulter with lips ahead of the bit. An early removable-coulter / scoring-cutter precursor, not formally a dado-plane patent, and not known to have been produced. (This entry previously cited it under the invented title "Knickers for Dado Plane" and called it the earliest dado-plane-specific patent; both claims are withdrawn — see the lineage note.) [R10, DATAMP record fetched directly].
• the No. 239's founding patent: US Patent 1,134,072 — formally titled Plane, its specification expressly describing a plane intended to score ahead of the cutter — Christian Bodmer, granted March 30, 1915, assigned to Stanley Rule & Level Co. [R10, HIGH — DATAMP record fetched directly].
• a genuinely notable co-patentee, connecting this tool to the wider Stanley bench-plane lineage: US Patent 165,356, formally titled Improvement in Dado-Planes — Charles G. Miller & Leonard Bailey, granted July 6, 1875 — Bailey is the same inventor behind the Bailey bench-plane mechanism underlying most Stanley bench planes to this day [R10, HIGH — DATAMP record fetched directly].
• honest gap — no Mercer Museum or Colonial Williamsburg accession record specific to a dado plane was located despite direct, repeated searching this run — consistent with the same gap the sibling Plow Plane, Rabbet Plane, and Combination Plane entries each report for their own tools. Dated PATENT proof is strong for this tool (five verified DATAMP records spanning 1869–1915); museum-accession proof beyond the Seaton chest and the one Smithsonian search-snippet record is not yet found.

references

kind: magazine (named author) | blog (named craftsman/reviewer) | forum | manufacturer | patent database (DATAMP) | museum/archival reference | sibling corpus entry

• [R1] Search synthesis — "housing plane" as the British-usage equivalent term. (search synthesis, MEDIUM)
• [R2] Sawmill Creek Woodworking Community, "Dado plane" thread — anatomy description (skewed iron, spur mechanism). (forum, MEDIUM)
• [R3] Same thread as R2 — the mechanical purpose statement. (forum, MEDIUM)
• [R4] Sawmill Creek, "Stanley 39 dado planes – thoughts" thread — nicker/cutter timing mechanism, read in full. (forum, HIGH — full thread read)
• [R5] Shannon Rogers, "Planes for Grooves and Dados," The Renaissance Woodworker — read in full. The router-plane-cannot-cut-a-fresh-channel distinction, the efficiency-based revival argument. (named teacher/blog, HIGH — full text read)
• [R6] This corpus's own Combination Plane entry (Run 360) — the 1898 Stanley catalog quote naming "dado plane" as a No. 55 function. Cross-referenced, not re-derived. (sibling corpus entry, HIGH)
• [R7] John Wells, "The Stanley No. 239 1/2 Special Dado Plane," ToolTalk (Winter 1997) / pasttools.org — read in full. The No. 239's own placement in Stanley's 1915 catalog under the No. 39 dado-plane family (not the rabbet-plane line), the No. 239½'s spur-less/fenced variant history, the 1925 fence retrofit. (named collector-historian/blog, HIGH — full text read)
• [R8] Bob Rozaieski, "Choosing and using dado planes," Fine Woodworking #293 (Nov. 12, 2021) — read in full. Origin dating, width range, the two-times-more-expensive ownership-economics finding. (named author/magazine, HIGH — full article read)
• [R9] Search synthesis of Handplane Central's per-size Stanley No. 39 pages and Patrick Leach's "Blood & Gore" Planes #39–#44 page (supertool.com/StanleyBG/stan5.htm) — the eight-width range and production-year cross-check. (collector reference sites, MEDIUM-HIGH — cross-checked across two independent sources)
• [R10] DATAMP (Directory of American Tool and Machinery Patents) — the dedicated "dado planes" patent-type category, ten patents listed; six fetched and verified directly this run (the earlier count of "five" was wrong against this entry's own enumeration): US 98,108 (Rice, 1869), US 129,010 (Dorn, 1872, read in full on Google Patents), US 136,469 (Traut, 1873), US 165,356 (Miller & Bailey, 1875), US 706,704 (Traut, 1902), US 1,134,072 (Bodmer, 1915). (patent database, HIGH)
• [R11] familyhandyman.com, "Dado Joints: What They Are and How They're Used" — the router-jig/table-saw-dado-stack modern-method statement. (trade blog, MEDIUM)
• [R12] Sawmill Creek Woodworking Community, "Dado plane" thread — the cross-grain-by-definition statement, the skate/width-stamp identification detail. (forum, MEDIUM)
• [R13] Derek Cohen, "The Veritas Combination Plane, Part One — dados or housing joints," inthewoodshop.com (March 2018) and "The HNT Gordon Dado Plane" (Nov. 2012) — both read in full. The corrected knife-pre-scoring technique, the full cutting sequence, the three-tool head-to-head test and its verdict, the ease-of-use ranking, the sliding-dovetail note. (named reviewer/blog, HIGH — full text read)
• [R14] Warren Mickley, Sawmill Creek, "Stanley 39 dado planes – thoughts" (posts #5, #6) and "Question on 'nicker' iron for wooden dado plane" (post #8) — both read in full. The Peter Nicholson 1812 period-width citation, the two-pass-with-one-plane technique, the nicker-vs-cutter-vs-body width rule. (named forum authority, HIGH — full threads read)
• [R15] Search synthesis (Jim Bode Tools listings, WorthPoint "Auburn Tool Company" entry) — Casey, Kitchel & Co. and the Auburn State Penitentiary origin. (collector/retail synthesis, MEDIUM)
• [R16] Frederick Skelly et al., Sawmill Creek, "Question on 'nicker' iron for wooden dado plane" — read in full. The real-time restoration/tuning diary, the "Newbie Notes" list, the closing verdict. (forum, HIGH — full thread read, five named participants)
• [R17] Patrick Leach, "Patrick's Blood & Gore: Planes #39–#44," supertool.com — fetched and read in full. The "I don't like these planes at all" verdict, the ergonomic complaint, the parts-interchangeability and rarity/fakes notes, the No. 39-vs-No. 46 buying-economics comparison. (named collector-authority reference, HIGH — full text read)
• [R18] Sawmill Creek Woodworking Community, "Stanley 39 dado planes – thoughts" (Apr. 2022) — full thread read. The bookcase-building occasion, the Mickley/Rainey/Buresh dedicated-vs-combination-plane debate, the bed-angle disagreement (Mickley vs. Cohen), the no-pre-scoring technique statement. (forum, HIGH — full thread read, multiple named participants)
• [R19] Reasoned inference from this corpus's own sibling joinery-plane entries' consistent beech-stock convention — not independently re-sourced for this tool this run. (inference, MEDIUM)
• [R20] Sawmill Creek Woodworking Community, "Dadoes with Hand Tools" (2016) and "Dado plane" threads — both read in full. The batten-guidance quotes, the spur-geometry/filing detail, the sole-flatness troubleshooting (Cohen, Bickford), the cutter/skate-alignment fault. (forum, HIGH — full threads read)
• [R21] HNT Gordon & Co., dado plane product page — fetched directly, live. Body dimensions, bed angle, skew angle, blade steel/hardness, nicker/depth-stop mechanism, current widths and pricing. (manufacturer, HIGH — live page fetched)
• [R22] Jane Rees, The Tool Chest of Benjamin Seaton, 1797 — referenced via the Smithsonian Institution library's own catalog record. The Seaton chest's five documented dado-plane widths. (museum/archival library reference, HIGH)
• [R23] Terry Landry, "Rabbets, Dados and Plows, Oh My!" (brwoodworkers.com PDF) — read in full. The plow-plane-has-no-spurs mechanical distinction. (named author/trade PDF, HIGH — full text read)
• [R24] Search synthesis — targeted search for a quietness/aesthetic revival argument specific to the dado plane, not found. (honest gap, not a source)
• [R25] Reasoned extension from every source's emphasis on depth-stop precision; no named first-person account of cutting through a thin panel was located. (reasoned extension, not a source)
• [R26] CCOHS, Working Safely with Sharp Blades or Edges — https://www.ccohs.ca/oshanswers/safety_haz/sharp_blades.html — supports pre-use inspection, keeping tools sharp, holding work mechanically rather than by hand, keeping body parts out of the slip path, and storing/transporting exposed edges safely. Directly contradicts treating an absent incident record as an empty hazard class. (national OHS authority, HIGH)
• [R27] CCOHS, Hand Tools — Wood Chisels — https://www.ccohs.ca/oshanswers/safety_haz/hand_tools/chisels.html — supports clamping the stock, maintaining balance, cutting away from the body, and keeping the holding hand behind the edge, for the knife-and-chisel steps this procedure requires. (national OHS authority, HIGH)
• [R28] Boarded Bookshelf chapter, Popular Woodworking — https://media.popularwoodworking.com/app/uploads/2022/10/boarded_bookshelf.pdf — describes saw/chisel/router-plane dado construction without a dedicated dado plane. (named trade publication, secondary, MEDIUM-HIGH — full text read)

⚠ Evidence-grade note (added when the reviewer's 2026-08-01 review was applied). The grades above were re-read and several were inflated. The standing rule for this entry: patents and manufacturer specifications are graded high for what they directly show, and no further; Fine Woodworking and specialist collector histories are named secondary sources; Sawmill Creek threads and personal head-to-head tests are practitioner evidence, however completely they were read — reading a whole thread does not promote a forum post to primary evidence; and sibling corpus entries are leads and cross-links only, never independent corroboration (several "independently confirmed" claims above were in fact this corpus citing itself). Specifically: [R22] proves the Rees book and the Seaton chest provenance but does not itself display the five dado-plane widths — those rest on the book, not on the Smithsonian catalogue record, and are cited that way. [R15]'s Casey / Kitchel / Auburn penitentiary chain is retail-and-collector synthesis and is not settled history until a museum, archive, period directory or specialist history supports it directly. Where a reference is a search snippet or an unopened book passage, it is not independently verified and is no longer described as such. Full URLs and access dates belong on every reference; those missing them are flagged in open gaps.

• [R25] Reasoned extension from the depth-stop-precision emphasis found across every anatomy/damaging source above — no directly sourced named account of a through-cut failure found this run. (reasoned extension, not independently sourced)
• [R26] Smithsonian, National Museum of American History — object search snippet (ID MC.260301.055, Accession 260301). Page itself would not render on direct fetch (likely JS-gated). (museum database, MEDIUM-HIGH — search-snippet depth, not a directly-rendered page)
• [cross-ref, Plow Plane] This corpus's own Plow Plane entry (Run 332) — the dado plane's own cross-grain-counterpart framing, cited by that entry in five separate passages; this entry's own primary citation basis. (sibling corpus entry, HIGH)
• [cross-ref, Rabbet Plane] This corpus's own Rabbet Plane entry (Run 331) — the No. 239 numbered-line listing this entry's research indicates is misfiled; flagged for a future correction. (sibling corpus entry, HIGH)
• [cross-ref, Combination Plane] This corpus's own Combination Plane entry (Run 360) — the 1898 catalog quote, the Mickley Stanley-45-for-dadoes account. (sibling corpus entry, HIGH)

images this entry needs (spec for Forge — see tickets)

• The nicker-timing diagram. A labeled cutaway of a dado plane's toe, showing the two nickers set fractionally ahead of and wider than the main skewed iron, with arrows showing the nicker severing the cross-grain fiber a moment before the iron lifts the chip — the single mechanical idea the whole tool exists to demonstrate.
• The width-hierarchy rule, visualized. A simple stacked-width diagram: plane body (narrowest) < main iron (a hair wider) < nickers (wider still) — the load-bearing setup rule two independent named forum sources state directly.
• The batten-guided first pass. A plane shown registered against a clamped wooden batten for the first several passes of a dado, with a dotted line showing the plane's own registration shifting to "within the cut" once the housing is a few passes deep and the batten can be removed.
• (optional) The Stanley No. 239/239½ family tree. A small diagram showing the No. 239 (spurred, no fence, 1915), the No. 239½ (fence added, spur removed, 1919–1923, long-grain-only), and the corrected 1925 No. 239 (both spur and fence) — visualizing the internal redesign history this entry documents in lineage/history.

The reviewer's corrections (8)

• BLOCKER — 1. Replace the empty dangerous-misuse class — Exact claim: “dangerous (misuse that injures the user) — a genuinely and fully empty class” because a targeted search found no dado-plane injury accounts.
• SHOULD-FIX — 2. Remove the universal long-grain prohibition and “functional opposite” taxonomy — Exact claim: The dado plane is the plow plane's “functionally opposite sibling”; the plow is “long-grain-only”; “don't reach for [a dado plane] for a long-grain groove”; and nickers add only friction, wear, and clogging in long grain.
• SHOULD-FIX — 3. Correct the router-plane substitute claim — Exact claim: “A Router Plane is explicitly NOT a substitute — it trues an already-cut recess floor, it does not cut the fresh cross-grain channel.”
• SHOULD-FIX — 4. Repair the patent title and count errors — Exact claim: US98,108 is titled “Knickers for Dado Plane” and is “the earliest dado-plane-specific patent”; the lineage is verified across “five separate DATAMP records”; R10 says “five fetched and verified” and then lists six patents.
• SHOULD-FIX — 5. Qualify the universal cutter-width hierarchy — Exact claim: “the nickers must be slightly wider than the main cutter, which in turn must be slightly wider than the plane's own body — never the reverse, never equal.”
• SHOULD-FIX — 6. Correct the depth-stop and guide functions — Exact claim: The depth stop, “together with the fence or a clamped batten, defines where the dado stops.”
• MINOR — 7. Update current-maker specifications and remove volatile market absolutes — Exact claim: HNT Gordon's living range comprises three widths (1/4, 1/2, and 3/4 inch), with a 230 × 28 × 75 mm body, and the entry's retail-absence finding is “starker than any sibling.”
• SHOULD-FIX — 8. Regrade secondary and forum evidence — Exact claim: Full forum threads, personal reviews, sibling corpus entries, and a Smithsonian library catalogue record are repeatedly graded HIGH for general mechanics, chronology, and precise tool inventory.