Tutorial 3 of 7
Joinery, back panels and cut sizes explained
Intermediate 12 min
How Kerfwise turns a cabinet size into part sizes — plinths, dados, rabbets, grooved backs, drawers, doors, hinges and edge banding — with worked numbers you can check.
Kerfwise does not guess part sizes; it applies explicit rules. Here they are with a worked example: a 600 × 870 × 560 mm base cabinet in 18 mm melamine on 150 mm legs.
Carcass
- Sides run full height: side height = cabinet height − plinth = 870 − 150 = 720 mm.
- Top, bottom and fixed shelves sit between the sides: length = inner width = 600 − 2 × 18 = 564 mm.
- With dado joints they grow by 2 × dado depth (T/3 = 6 mm) → 576 mm; with rabbets by 2 × rabbet depth (T/2 = 9 mm) → 582 mm.
- Butt + screws, dowels, confirmat, pocket screws and cam-and-dowel do not change lengths; they change holes and hardware (e.g. dowels Ø8 × 12 in the side and Ø8 × 25 in the panel edge, 50 mm from each end and at most 150 mm apart).
Change the joint under Carcass & back → Carcass joinery and watch the cut list and the drilling on the part drawings update.
Back panels
| Back type | Size rule | Example |
|---|---|---|
| Grooved (8 mm HDF in 8 mm grooves) | (inner height + 2 × groove) × (inner width + 2 × groove) | 700 × 580 with a full top |
| Grooved, base cabinet with rails | inner height + T + groove (runs up to the carcass top) | 710 × 580 |
| Inset (fitted between all four panels) | inner height × inner width | 684 × 564 |
| Nailed on the rear edges | outer size − 2 mm | 718 × 598 |
A grooved back sits 16 mm from the rear edge, so the usable depth for shelves and drawers becomes 560 − 16 − 8 = 536 mm.
Doors and hinges
- Full overlay: width = cabinet width / doors − gap (3 mm) → one door 597 mm, two doors 297 mm each; height = carcass height − gap = 717 mm.
- Inset: (opening − (n + 1) × gap) / n.
- Hinges per door by height: ≤ 900 mm → 2, ≤ 1600 → 3, ≤ 2000 → 4, taller → 5, placed 100 mm from the ends. Each hinge gets a Ø35 × 13 mm cup 22.5 mm from the door edge plus two Ø8 dowel holes; the mounting plates go on the side panel 37 mm from the front.
Drawers
- Slide length = longest standard length ≤ inner depth − 10 mm → 500 mm here.
- Box width: side-mount slides need 12.7 mm per side (564 − 25.4 = 538.6 mm); undermount slides use the “inside width = opening − 42 mm” rule (with 15 mm sides: 552 mm outside).
- Box height = front height − 40 mm (side-mount) or − 47 mm (undermount).
- Box front/back length depends on the drawer joint: butt or dowel = box width − 2t, dado = box width − t, dovetail = full box width.
Shelves and the 32 mm system
Adjustable shelves are inner width − 2 mm (1 mm play each side), set back 20 mm, and the sides get two rows of Ø5 holes at 32 mm pitch, the first row 37 mm from the front.
Edge banding and cut sizes
Each part has four edges: L1 (front/visible long edge), L2, W1, W2. With Deduct edge banding from cut sizes on, the banding thickness is subtracted: a 717 × 597 door with 2 mm ABS on all four edges is cut at 713 × 593.
You can verify all of this yourself in Drawings (key 8), which lists the key dimensions of the selected cabinet next to its front, side and top views.