Knock-Down Workbench
A 1,500 mm maple bench that bolts together and unbolts again: the rails clamp to the outside of the legs, so every joint is a bolt through both members with a nut you can reach.
Designthe dimensions everything else is derived from
Cut list sizes are finished sizes. Add 5 mm to the width and 25 mm to the length of every solid-wood part for saw kerf and planing, and buy boards oversize by one thickness so a bowed board can be flattened rather than relegated.
Materialswhat each part is made from, and why
All materialsCut listfinished sizes, worked back from the design
| Part | Qty | Finished size | Stock |
|---|---|---|---|
| Top | 1 | 1500 x 600 x 40 mm | Maple (Hard Maple) |
| Leg | 4 | 90 x 90 x 860 mm | Fir (Douglas) |
| Upper long rail | 2 | 1500 x 90 x 40 mm | Fir (Douglas) |
| Upper short rail | 2 | 520 x 90 x 40 mm | Fir (Douglas) |
| Shelf | 1 | 1320 x 420 x 18 mm | Birch Plywood |
| Shelf cleat | 2 | 420 x 40 x 40 mm | Fir (Douglas) |
Fastenersquantities and lengths that follow from the joints
All standards| Item | Qty | Grip | Standard |
|---|---|---|---|
| M8 x 150 hex bolt | 20 | 130 mm | ISO 4017 |
| M8 x 100 hex bolt | 8 | 80 mm | ISO 4017 |
| M8 plain washer | 56 | — | DIN 125 A |
| M8 nylon-insert nut | 28 | — | DIN 985 |
Grip is the sum of the clamped thicknesses. A bolt has to clear the nut by two full threads, which is what sets the length that appears in each row — not a preference.
Toolsand what each one is for on this job
All toolsOrder of workthe sequence, and where it is not free to change
- Cut the four legs to 860 mm. 900 mm finished height less the 40 mm top.
- Clamp each leg to its rails and bore through all three at once. Drilling the parts together is what makes the frame square.
- Bolt the two long rails and two short rails to the four legs, snug rather than tight, and check the diagonals match.
- Fit the two shelf cleats at 250 mm above the floor.
- Drop the shelf in. It is not fastened: it lifts out for cleaning and it does not fight the frame when the timber moves.
- Counterbore eight 20 mm holes in the top, drill through, bolt down, and plug the counterbores with maple dowel cut flush.
Where it goes wrongthe three failures worth designing out
- Tightening a bolt into softwood with no washer under the nut. The nut crushes the fibres, the clamp disappears, and the bench racks.
- Running the bolts up with an impact driver. The driver will exceed what the timber can take and pull the head into the rail.
- Drilling legs and rails separately. A millimetre of difference per joint is a centimetre across the frame, and the top will not sit flat.
Frequently asked questions
Why bolt the rails to the outside of the legs instead of between them?
Because of where the nut ends up. With the rail between the legs the bolt would have to be driven into the end grain of the rail, which needs a barrel nut or a lag screw. With the rail on the outside face the bolt passes through both members and the nut is on the inside face of the leg, where you can reach it with a spanner. Both members are then in compression, which is the condition the bolt is designed for.
Is there room to unbolt it later?
Yes, and that is the point of the design. Every nut is accessible with the top off, no joint is glued, and no fastener is driven into end grain. A bench that has to move house in two years is a bench that should come apart in twenty minutes.
Can I substitute wood screws and skip the bolts?
For a bench, no. A wood screw holds by compressing the fibres around its shank and it cannot be re-tightened once those fibres are crushed; a bolt with a washer and a nut can. This database does not carry wood screw standards, so the sizes you would need are not published here either.