Joinery and fixings

A joint on a drawing is a promise about a machine setting. "Doweled" means somebody drills holes at a spacing, to a depth, in a pattern that has to meet its partner. You cannot draw a joint you cannot picture, and you cannot check one you have not dimensioned.

The rules that apply to every joint

The standard lets the shop choose the joint and then sets a floor under it (AWS Section 10.4.7, rule 22):

• Cabinet members are "securely fastened together, using one or more of the approved methods, at the manufacturer's choice, including: dadoes, lock joints, plows, rabbets, dowels, dowel screws, or biscuit splines".
• Casework is assembled square and true within 1/32" (0.8 mm) top to bottom and 1/16" (1.6 mm) diagonally.
• All joints are "securely glued".
• Mechanical fasteners in the body, back and drawers go at 4" (101.6 mm) centres maximum, with at least two per joint. Face frames may go to 8" (203 mm).
• No exposed fasteners on exposed exterior surfaces. Where exposed fasteners are allowed, they are plated, and "bugle drywall screws are not permitted".
• Mechanical fasteners are not required at dovetail, miter fold, mortise and tenon, and lock miter joints.

Anything else is allowed "provided it is fully documented in a text/illustration explanation, and each material application has been independently tested" against the standard's structural tests (rule 10.4.7, 4). A shop with its own house joint can use it, but somebody has to show it works.

Who chooses matters for the drawing. The standard makes joinery the manufacturer's choice. So the drafter's first job is to find out what this shop does, draw that, and state it once in the general notes. The Woodwork Institute sample does exactly that on its specification sheet: JOINERY TYPE: DOWEL CONSTRUCTION and CAB. CONSTRUCTION- 8mm x 30 mm WOOD DOWELS SPACED PER W.I. SECT. 14/15.

The joints, one by one

Dado, rabbet and plow

Three cuts made with a blade or a router bit. Each one locates a panel in another before glue or screws go in.

Joint	AWS description	Typical use in casework
Through dado	"Conventional joint used for assembly of case body members. Dado not concealed by application of case face frame."	Fixed shelves, bottoms into ends
Blind dado	"Variation of Through Dado with applied edge 'stopping' or concealing dado groove."	Where a banded front edge shows
Stop dado	"Another method of concealing dado exposure. Applicable when veneer edging or solid lumber is used."	Same, cut short of the front edge
Rabbet	An edge step; the standard requires exposed ends to be "rabbeted or plowed to receive backs"	Backs into exposed ends; drawer sides into fronts (Economy)
Plow (groove)	A groove along the grain	Backs into ends; drawer bottoms into sides, at least 3/8" (9.5 mm) up from the bottom edge (rule 7.14.1.3)

Two rules tie these cuts to other chapters. Dadoes and lock joints "shall not run through the edgeband" at Custom and Premium (rule 6.5), so a banded front edge needs a stopped dado. And a plowed back needs a shoulder of at least 1/2" (12.7 mm) (rule 14.6), which sets how far the back sits in from the rear edge (chapter 10).

Draw the cut to the sheet you will actually get. Hardwood plywood may be up to 3/64" (1.2 mm) under nominal (chapter 11). A dado dimensioned at a nominal 3/4" is a loose joint. Dimension it "to suit material" or to the measured thickness.

Dowels

The AWS calls the dowel joint "an established industry standard assembly method" and notes it "is often based on 1-1/4" (32 mm) spacing of dowels". That spacing is not an accident. It is the pitch of the 32 mm system, the grid of 5 mm holes that European hardware mounts to (chapter 15). A shop that line-bores its sides can drill dowel holes and hardware holes from the same grid.

The minimums (rule 22.3.1.5):

Rule	Value
Dowel size, minimum	5/16" × 1-3/16" (8 × 30 mm)
Dowels per joint, minimum	2
First dowel from the front	2" (51 mm) maximum
Spacing	3-21/32" (96 mm) maximum, as drawn in the rule's diagram
Assembly	Glued and clamped

For drawer boxes the spacing tightens: dowels at 1-1/4" (32 mm) centres maximum for joints up to 4" (102 mm) long, and 2-1/2" (64 mm) for longer joints (rule 7.4.2).

Dowel screws (Confirmat)

A one-piece case screw with a coarse thread and a shank that fills its hole. The AWS rule (22.3.1.6):

Rule	Value
Size, minimum	9/32" × 2" (7 × 50 mm)
First screw from the front	2" (51 mm) maximum
Spacing	5" (127 mm) maximum; the diagram shows 128 mm
Glue	"Glue is not required"

Häfele sells one under the name Confirmat. Würth Machinery, a distributor, lists Häfele's #7 × 50 mm Confirmat screw with the maker's feature claims: "Only a single drilling operation for side panels and shelves" and "Consistently secure joints are assured even with repeated assembly and disassembly". It sells the matching drill as a "5mm x 7mm HSS Step Drill Bit for Confirmat". No glue and repeat assembly suit work that ships flat, or has to come apart to get through a door.

The screw goes through the face of one panel into the edge of the other. That edge is the panel's weak direction. Roseburg rates its 3/4" SkyBlend particleboard at 250 lbf screw holding in the face and 180 lbf in the edge. The Wood Handbook warns that "care must be taken when tightening screws in particleboard to avoid stripping the threads" (Chapter 8). Read together: the joint's strength lives in the panel edge, so a stripped hole there needs a repair, not a second drive.

Biscuits

A beech wafer glued into two matching slots. The AWS rule (22.3.1.7): biscuits "a minimum #20 or equal", the first no more than 2" (51 mm) from each edge or end to the centre of the plate, the rest at 6" (152 mm) centres maximum, glued and clamped. Biscuit splines are also a permitted drawer box joint at Custom and Premium (rule 7.2.6).

Lamello, which makes the original system, publishes the sizes:

Lamello biscuit	Size
No. 0	47 × 15 × 4 mm
No. 10	53 × 19 × 4 mm
No. 20	56 × 23 × 4 mm

All three fit a 4 mm groove cut with Lamello's Ø100 × 4 mm standard cutter. The AWS minimum, #20, is the largest of the three.

Loose tenons (Domino)

A machined tenon glued into two matching mortises. The AWS names "mortise and tenon, dowels or loose tenon glued under pressure" as the Premium joinery for stile and rail doors (rule 8.11.1.9.3). Festool's manual for the DOMINO DF 500 gives the machine's limits and its own sizing advice:

• Mortising bits of 5, 6, 8 and 10 mm; maximum mortising depth 28 mm.
• Tenon thickness about one third of the workpiece thickness in hardwood, "why 8mm Domino tenons are the most common for joining ¾-inch lumber".
• For plywood, "it is best to maximize the strength of the substrate by minimizing the thickness of the tenon".
• In most cases the mortise depth is half the tenon length.

A Domino is a hand-held machine. It suits face frames, doors and one-off furniture. It does not come off a CNC nesting table, and a drawing that calls for it on every carcass joint is asking a machine shop to go back to hand work.

Pocket screws

A screw driven at an angle from a pocket bored in one part. The AWS lists "pocket screwed" among permitted face frame joints (rule 27.4.4) and draws a pocket screw joint for fixing a finished end to a face frame. It is quick, needs no clamps, and hides on the back of a frame. Its rule is the face frame rule: at 8" (203 mm) centres maximum, glued (rule 22.3.1.1).

Mitres

A mitre hides both end grains and shows none. The AWS names several: the shoulder mitre, the miter fold (a V-groove through the face to within the laminate, then folded), the lock miter, the spline mitre, and the biscuit-splined mitre. Two rules make them grade markers:

• At Premium face frames, "exposed corners shall be shoulder mitered, lock mitered, spline mitered, or mitered with a biscuit spline" (rule 27.4.5.3).
• Miter-folded drawer boxes, cored with particleboard or MDF with the grain running horizontal, are permitted at Economy and Custom, not Premium (rule 7.2.3).

Dovetails and drawer joints

The AWS drawer rules show how joinery tracks grade (rule 7.2):

Drawer side joint	Economy	Custom	Premium
Nailed to sub-fronts and backs	Yes	No	No
Rabbeted to fronts or sub-fronts and backs	Yes	No	No
Miter folded, particleboard or MDF core	Yes	Yes	No
Multiple dovetail, solid wood or 7-ply plywood, no extra fasteners	No	Yes	Yes
Doweled or dowel screwed	No	Yes	Yes
Biscuit splined	No	Yes	Yes
Lock jointed and nailed	No	Yes	Yes

The nomenclature pages add the French dovetail, "for joining drawer sides to fronts when fronts conceal metal extension slides or overlay the case faces", and the drawer lock joint. At flush overlay without a sub-front, drawer sides are "blind dovetail dadoed to the front" (rule 7.3). Chapter 14 covers the rest of the drawer.

Splines

A strip let into two grooves, "used to strengthen and align faces when gluing panels in width or length, including items requiring site assembly" (AWS nomenclature). Any joint the installer makes on site, such as a long top or a panel run too big to ship in one piece, wants an alignment device drawn and specified.

Which joints fit which shop

No document in hand counts how many shops use each joint, so this section reasons from the documents rather than citing a survey.

• Drilled joints fit machine shops. Dowels and dowel screws are holes. The AWS ties dowel spacing to 32 mm, Blum's line-bore manual builds a whole cabinet on a 32 mm grid, and Häfele sells the Confirmat on "a single drilling operation". A boring machine or CNC router makes all of them from the same program that makes the hardware holes.
• Cut joints fit both. Dadoes, rabbets and plows come off a saw, a shaper or a router, by hand or by machine.
• Fitted joints fit hand work. Dovetails, mortise and tenon, shoulder mitres and loose tenons need setting up per part. The standard reserves several of them for Custom and Premium work.

The practical test is simple. Ask the shop floor what it makes, and draw that (chapter 28).

Screws in wood and panels

Three facts from the Wood Handbook belong in every drafter's head:

• Screws in end grain "should average 75% of the load sustained by screws inserted in the side grain", when splitting is avoided (Chapter 8).
• In particleboard, "tapping screws are commonly used ... where withdrawal strength is important", and overtightening strips the thread (Chapter 8).
• In MDF, every product in Table 12-6 holds a screw better in its face than in its edge.

Plywood is the exception on edges: its cross-laminated layers make it "resistant to splitting, allowing fasteners to be placed very near the edges of a panel" (Chapter 11).

Fixing the cabinet to the building

Joinery holds the box together. Fixings hold it to the wall and floor, and the Woodwork Institute sample draws both on its own sheets.

• Timber stud wall. #14 SMS through the cabinet into 2x6 FLAT BLK'G (BY GENERAL CONT.), with the screw 3" MAX. from the top and 2" MAX. IF LINE BORE.
• Metal stud wall. The same screw into 6"x 16 GA. CONT. (BY GENERAL CONT.) backing.
• Wall screws, detail-standards sheet. #14x3" MODIFIED TRUSS HEAD SCREW, TYPE #17 TIP @ 16" O.C. MIN. 2-PER CABINET, 2" TO CENTER OF BACKING, into METAL OR WOOD BACKING (BY OTHERS), with a screw cleat and a CONTINUOUS HOT MELT GLUE JOINT.
• Toe kick. A 16ga 3"x3"x3" METAL ANGLE shot to the floor with a .145 DIA PIN @ 16" O.C., minimum two per cabinet, and #8 x 1 1/2" SSM @ 16" O.C. into the toe.

Every one of those details names who supplies the backing. That is the standard's allocation too: blocking and backing in the wall "are not to be furnished or installed by the architectural woodwork manufacturer or installer" (AWS 10.1, 14.1), and "it is the design professional's responsibility to evaluate the fastening methods required" (AWS 10, Contract documents). The sample also refers to its own seismic appendix, and the standard says seismic requirements, where they apply, "shall be so specified". Chapter 18 covers installation (chapter 18).

How joints read in a section

A section is only useful if the reader can tell one part from the next. The Student Handbook for Basic Drafting gives the base convention: section lines "distinguish between two separate parts that meet at a given point. Each part is lined or hatched in opposite directions". Both drawing sets in hand add their own shorthand:

• Solid members cut in section, such as stretchers, nailers and blocking, are drawn as a rectangle with an X through it.
• The Woodwork Institute details show dowels and screws as drawn parts with a leader and a note (DOWEL, 3/4" BASE DOWELED @ EA. END (TYP)), so the reader sees the joint and its callout together.
• Its joinery details are grouped on "typical joinery details" sheets, lettered A to X, and called from one isometric reference view, so each joint is drawn once and referenced everywhere it recurs.

What to dimension on a joint detail:

1. Dowels and dowel screws: diameter × length, count or spacing, and distance of the first from the front edge.
2. Dadoes, rabbets and plows: depth, width (to suit material), and setback from the edge.
3. Biscuits and tenons: size and spacing, or "per standard".
4. Fasteners to the building: type, size, spacing, minimum per cabinet, and who supplies what they fix into.

Balance that against clutter. An outsourcing vendor's blog, Ripudaman Singh's "Essential Details You Should Look For in Millwork Drawings", argues that standard screw type and size "can be omitted" so they do not bury the information only the drafter can supply. The workable rule: state the house joinery once, in the general notes, as the Woodwork Institute sample does, and draw a detail only where a joint departs from it.

Knock-down fittings

The AWS includes "shelving, built up or machined and knocked down" in casework scope, and its dowel screw rule covers one knock-down joint. Cam-and-bolt connectors and other proprietary fittings are the maker's products, governed by the maker's documents. If your job uses one, cite that document on the sheet, as chapter 15 does for hinges.

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Sources

• Architectural Woodwork Standards, 2nd Edition, 1 October 2014, © AWI, AWMAC, WI, full text hosted by the Woodwork Institute. Section 10, printed pp. 285 (contract documents, seismic), 292–293 (construction detail nomenclature: dowel, dowel screw, dadoes, dovetails, mitres, spline, pocket screw), 298 (blocking by others), 310–312 (joints, flatness, alternative joinery, edge and dado rules, drawer joints and spacing), 315 (stile and rail joinery), 317 (backs), 322 (joinery rule 22: fasteners, dowels, dowel screws, biscuits), 326 (face frames). Superseded for jobs bid under later editions; see chapter 19. Primary (superseded edition).
• USDA Forest Products Laboratory, Wood Handbook, FPL-GTR-190, Centennial Edition, April 2010. Chapter 8, Fastenings: end-grain withdrawal, fastening of particleboard. Chapter 11: plywood edge fastening. Chapter 12, Table 12-6: MDF screw holding. Primary.
• Roseburg Forest Products, SkyBlend particleboard technical data sheet, 16 Oct 2023. Face and edge screw holding. Primary for the product.
• Lamello, Lamello System brochure, English (lamello.com). Biscuit sizes No. 0, 10 and 20, the 4 mm groove, the Ø100 × 4 mm cutter. Primary.
• Festool, Domino DF 500 Tenon Joiner, Supplemental User's Manual (copy hosted by Waterfront Woods). Bit range, maximum depth, tenon sizing and placement advice. Primary.
• Würth Machinery, product listings for Häfele Confirmat screw #7 × 50 mm (Häfele 264.47.138) and the Confirmat step drill (Häfele 001.22.645), wurthmachinery.com. Screw size, single drilling operation and repeat-assembly claims, drill name. A distributor repeating the maker's feature list. Claimed.
• Blum, Inc., Process 32, drawing BUS0126, 2003–04, hosted by WOODWEB. The 32 mm line-bore grid used as the basis for a whole cabinet. Primary.
• Student Handbook for Basic Drafting (research/ptech_drafting_handbook_new.pdf), "Section Lines". General drafting, not millwork-specific. Primary for the drafting convention.
• Woodwork Institute, Sample Shop Drawings. Specification requirements sheet (joinery type and dowel size), typical joinery details sheets 4–7 of 10, anchorage details, the detail-standards sheet (wall screws, toe kick anchorage). Document.
• A residential millwork submittal, 16 sheets, revision 0, section sheets 09–16: the X-box convention for solid members in section. Not reproduced: live job. Document.
• Ripudaman Singh, "Essential Details You Should Look For in Millwork Drawings", hitechdigital.com, 2 July 2024. The argument for leaving standard fastener details off the drawing. An outsourcing vendor's marketing. Claimed.

Left out for lack of a source I could open: Häfele's own drilling specification for the Confirmat (its product pages refused automated access, so the hole sizes here are the distributor's product name only), cam-and-bolt connector dimensions, pocket screw sizes, and any count of which joints shops actually use.