Prepare and reference the stock
A joint can only be as accurate as the parts it joins. Veritas starts its dovetail instructions with boards dressed flat, to even thickness and with square ends, before any layout, and every joint method assumes the same. Then choose one face and one edge of each part as the references and mark them, and lay out and cut every joint from those. Leigh's jig depends on it — the same face of every part goes against the jig — and so does work by hand: gauged from one face, any small error repeats on both parts and cancels out. Stock preparation is in hand planes and cutting straight; reference faces in BenchRoot's reference method.
Marking a joint
Mark the references
Face side and face edge on every part, before anything else.
Knife the shoulders
A knife line is finer than a pencil line and gives a chisel or saw a place to register. Square it round from the reference face — see measuring and marking and squares.
Gauge from the reference
Set the marking gauge once and run every line that should match from the reference face — see marking gauges.
Mark the waste
An X in every piece to be removed, as Veritas does, so no cut lands on the wrong side of a line.
Cut on the waste side
- Saw beside the line, not on it. The kerf goes into the waste so the line survives on the part; the joint is then pared to the line. See backsaws and Japanese saws.
- Pare, do not hack. Take waste in small bites, starting short of the line and finishing in it, with the work held down. OSHA's hand-tool guidance is to secure the work with clamps or a vise so both hands are free for the tool. See using a chisel.
- Machine joints the same way. A box joint or a routed tenon is set up on test pieces of the finished stock, as Freud and Leigh both direct, and adjusted before the real parts are cut. Leigh notes that different species do not always cut to quite the same fit.
Fit before you glue
| Joint | Maker | Right fit |
|---|---|---|
| Mortise and tenon (routed) | Leigh | About 0.005 in loose: pushes together fairly easily, does not fall apart; a mallet means too tight |
| Box joint | Freud | Goes together easily but with slight friction |
| Dovetail (hand-cut) | Veritas | Fits together with very little effort |
Each maker's description for its own jig, cutter or guide.
A dry fit tests more than tightness. Assemble the whole piece without glue, with the clamps you will use, and check that it closes and is square; then mark the parts so they go back in the same order. The Wood Handbook adds two reasons to cut the glue surfaces cleanly and close to glue-up. It recommends surfacing within 24 hours of bonding, so the wood is clean and has not changed shape, and flat, parallel surfaces so the glue forms a uniformly thin layer. Its micrographs show a planed surface as ideal for bonding and one sanded with coarse 36-grit paper with layers of crushed cells. A joint that needs glue to fill its gaps is a loose joint. Clamping is in clamps, bar clamps and corner clamps.
- Next: choose the joint for the job in choosing a wood joint, then see dovetails, mortise and tenon or box joints.
- Practise: the dovetailed box and the kumiko lattice panel use these techniques on real pieces.
Fitting a joint
- Stock flat, to thickness and square before layout
- Reference face and edge marked on every part
- Knife and gauge lines from the reference
- Every cut on the waste side, pared to the line
- A dry fit that closes without force, then a full dry assembly
- Glue surfaces cut cleanly, close to glue-up
Sources
Fit descriptions are each maker's for its own jig, cutter or guide; together they describe the same feel. Bonding findings are the Wood Handbook's (2021). Glue selection and clamping times publish separately, on the glue pages.
- 1.
FMT Pro Frame Mortise & Tenon Jig User Guide. Leigh Tools (a Lee Valley Tools company).
Used for: The same face of every part referenced against the jig; a best fit about 0.005 in loose, pushing together fairly easily but not falling apart, a mallet meaning too tight; mortises slightly deeper than the tenon; different species not routing to quite the same fit.
- 2.
SBOX8 Box Joint Instructions. Freud (instruction sheet, distributor-hosted copy).
Used for: A box joint that goes together easily but with slight friction, adjusted on test pieces of the finished stock before cutting the real parts.
- 3.
Dovetail Saw Guides — instructions (INS-622_B). Veritas Tools Inc. (Lee Valley), 2018.
Used for: Boards dressed flat, to thickness and with square ends before layout; waste marked with an X; cutting on the waste side of the line; a dovetail that fits with very little effort.
- 4.
Chapter 10: Wood Adhesives: Bond Formation and Performance. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Surfacing within 24 h of bonding for a clean, wettable surface that has not changed shape; flat, parallel surfaces for a uniformly thin glue line; a commercially planed surface shown as ideal for bonding and coarse 36-grit sanding as crushing layers of surface cells; shaped joints that cannot be machined to meet perfectly bonding no better than flat ones.
- 5.
Hand and Power Tools (OSHA 3080). Occupational Safety and Health Administration, 2002.
Used for: Securing work with clamps or a vise so both hands are free for the tool.
About this guide
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