Build a Simple Mobile Workbench on Castors

Why a Mobile Bench Beats a Fixed One in a Small Workshop

If your workshop doubles as a garage, a spare bedroom or half a shed, you already know the problem: whatever you build ends up in the way of everything else. A bench that stays put forces you to work around it. A bench that rolls out when you need it, then tucks against the wall when you don't, gives you a proper work surface without permanently surrendering the floor.

The trick is making a mobile bench that doesn't behave like a trolley. It needs to be heavy enough to take a plane or a mallet blow without skittering, rigid enough that the top doesn't rack when you push it, and stable enough that leaning on one corner doesn't tip it. Locking castors do most of that work, but the frame and the top have to pull their weight too.

Sizing It to Your Space and Your Timber

Before you cut anything, measure the gap you intend to store it in. A bench that fits with 20mm to spare is a bench you'll actually put away. For most small workshops, a top around 1200mm long by 600mm deep is the sweet spot: long enough for a mitre saw or a vice plus a work area, short enough to wheel through a standard 762mm doorway.

Height matters more than people expect. Aim for the top surface to sit level with your wrist when your arm hangs relaxed — usually somewhere between 850mm and 900mm for most people. If you do a lot of hand planing, go slightly lower; if you do fine assembly work, slightly higher.

For materials, a sensible shopping list is:

• Legs and rails: 44mm x 94mm CLS timber or 45mm x 70mm PAR softwood — four legs at 800mm, plus eight rails
• Top: 18mm plywood or MDF, doubled up for a 36mm surface, or a single sheet of 25mm MDF if weight isn't a concern
• Lower shelf: 12mm plywood or 18mm MDF, sized to sit inside the frame
• Castors: four 75mm or 100mm castors, all with brakes, rated at least 50kg each
• Fixings: 8mm coach bolts or 6mm x 100mm screws for the frame, plus washers

Building the Frame Square and Stiff

Cut the four legs to length first, then cut the rails. A simple and stiff arrangement is two long rails at the top of the front and back faces, two short rails at the top of the sides, and the same again about 250mm up from the floor for the shelf. That gives you a box within a box, which resists racking far better than four legs joined by a single apron.

Drill pilot holes before you drive anything in — softwood splits easily near the ends of rails. Work on a flat floor and check diagonals as you go: measure corner to corner on the top frame, and adjust until the two figures match. Clamp a temporary diagonal brace across the frame while you fasten it if it helps hold things true.

Once the top frame is together, fit the lower rails and drop the shelf in. Fix it down with screws through the rails, and add a couple of cross-battens underneath if the shelf is more than 900mm wide. The shelf adds a surprising amount of rigidity, and it's the obvious home for the tools you reach for constantly.

Castors: The Bit That Decides Whether It Works

Buy castors with a brake on the wheel and a swivel lock if you can find them, and buy them all braked rather than two braked and two free. Uneven braking is how benches walk across the floor mid-cut.

Mount each castor on a plywood pad at least 18mm thick and roughly 100mm square, screwed and glued to the underside of the leg. Bolting straight into the end grain of a leg is weak; the pad spreads the load and gives the castor bolts something solid to bite into. Use bolts rather than screws wherever the castor body allows it.

A word on wheels: 75mm castors roll over cables and small offcuts better than 50mm ones, and 100mm are better still, but taller castors raise the bench and can make it feel tippier. If your floor is reasonably smooth, 75mm is a good compromise. Push the bench around once it's assembled and listen — a bench that rattles is a bench with loose fixings.

The Top, Dog Holes and a Vice

Cut the top slightly oversize, fix it down, then trim it flush with a flush-trim bit or a sharp plane. Overhang the top by about 50mm on the front and sides so you have somewhere to clamp, but keep it flush at the back if the bench lives against a wall.

Dog holes turn a flat surface into a workholding system. Drill 19mm or 20mm holes — match whatever bench dogs you plan to buy or make — and space them on a 96mm grid, which is the common standard. Drill them square to the top; a drill guide made from a scrap of thick timber with a hole bored through it will keep you honest. A row along the front edge and a couple of rows further back gives you plenty of options for planing stops and holdfasts.

If you're fitting a vice, do it before you finish the top. A woodworking vice on the front left corner is the traditional spot, and you'll want to reinforce underneath with a block of hardwood between the vice jaws and the bench frame.

Finishing and Living With It

Sand the top to about 180 grit and give it two or three coats of a drying oil or a hard wax oil. Skip varnish — you want a surface you can repair with a scraper, not one you have to strip. Wax the underside of the shelf and the frame lightly so dust doesn't cling.

Once it's in use, check the castor bolts and frame fixings after the first fortnight, then every few months. A mobile bench takes more racking force than a static one, so treat it as a machine that needs occasional tightening rather than a piece of furniture. Get that right and you'll wonder why you waited so long to build it.