I wanted a robust portable workbench that was quick to assemble and dis-assemble, and that I could easily fit in the car. It needed to be light enough for one person to handle, but sturdy enough to carry a vice and a drill press. The challenge was to use hinges for fold-up legs but to make the bench stable at the same time. This was achieved with bolt-on diagonal braces, which attach & detach quickly with engineers bolts and wing nuts. The bench top is 1200mm x 650mm, height is 735mm (to match another table I use). The design is for indoor use (the fixings and boron treated framing timber would have a limited life if left out in the weather)
Step 1: Materials
A half sheet of 18mm plywood (1200 x 1200 x 18mm). 10m total length of 75 x 50 gauged (about 65 x 45mm) boron treated timber. The boron treatment makes it pink. Packet of 10g x100mm self-drilling screws, Jar of 8g x 45mm self-drilling screws, 8 x 100mm x 8mm engineers bolts and wing-nuts. 4 Hinges (about 65mm wide). 8g x38mm wood screws for fixing the hinges.
Step 2: Cut the Bench Top & Shelf
I cut the plywood into a 650 wide 550 wide pieces (1200 long). The smaller piece is the shelf. I used the 75 x 50 timber to support the plywood off the floor. I clamped a ply offcut from another project as a straight edge 'fence' / guide for the circular saw.
Step 3: Cut the Top Frame
The bench top overhangs the frame by 50mm all around, so the frame will be 1100 x 550mm. I deliberately didn't mitre the corners because some of the hinge screws would have been to close to the mitre. Cut two pieces of 75x50 1100 long & two pieces about 420mm long (so that the width will be 550mm).
Step 4: Assemble the Top Frame
Pre-drill the 1100mm timbers for two 100mm self-drilling screws. Use the square to set the corners square. Screw the frame together.
Step 5: Fit Spacer
The spacer is used so that the legs will lie flat on each other when folded up. This does mean that the two sets of legs are cut to different lengths. I counter-sunk the holes about 20mm so that the 45mm self-drilling screws would get a good hold on the frame below.
Step 6: Cut Legs & Fit Hinges
Very carefully measure, check, measure again & cut carefully the legs (remember one pair of legs is shorter than the other because of the spacer in the frame). You don't want a rocking bench! Screw the hinges to the frame and the legs so that the legs bear directly on the frame. The hinges should not have to carry any weight. The frame is very wobbly at this point. Be careful it doesn't fall on anyone.
Step 7: Strengthen Leg Frames
This step could have (or should have been) be done before fitting the legs and hinges. Measure and cut to fit a length (about 400mm) of 75 x 50 timber and screw fix (with 2 x 100mm self-drilling screws each side) between each pair of legs. This makes a 'goal post frame' out of the legs which stiffens the bench in it's short direction very well. This 'beam' also supports the shelf later on. I set the height of the beam so that when the table is folded flat the beams sit one on top of the other.
Step 8: Make Diagonal Braces
I made four diagonal brace pieces. Each is 300mm x 40mm with an 8mm hole 20mm from each end (260mm centre to centre). I used some 12mm tri-board, but some 12mm pine or similar would have been fine. The corners are cut so the braces can rotate and not catch on the underside of the benchtop.
Step 9: Fit Diagonal Braces
The braces need to be fit such that the legs are fully open (and should be perfectly vertical). Drill 8mm holes for the 8mm engineers bolts in the bench top frame and legs. Watch out for the screws in your hinges (you might need to adjust the brace length, bolt holes and/or brace angle slightly to miss drilling through those screws). Using the brace pieces as a template helps get the holes in the right place. Label each brace and the corner of the frame (each corner could be a slightly different fit) - mine were. Test fit the bolts and wing-nuts. I had to run the drill through the holes a few extra times to loosen the hole enough for the bolts to be snug (but not too tight or too loose).
Step 10: Fit Bench Top
Choose the best side of the ply to go face up. Mark out the screw positions so that they will land in the middle of the top framing timber. I spaced the 8g x 45mm self-drilling screws evenly at no more than 150mm centres. Position the ply centrally over the frame (with equal overhang all around). Screw in the 4 corners, each time checking that the ply hasn't moved. Progressively fit the other screws. I found my cordless drill had enough power to 'self counter-sink' the screw heads below the surface of the ply, so there was no need to pre-drill & counter-sink the holes.
Step 11: Cut and Fit the Shelf
The 550mm wide ply off-cut makes the shelf. Cut to 1100mm long (to match the frame length) and cut out the 4 corners to fit around the legs. I cut the corners a little larger, so the shelf was a relatively loose fit.
Step 12: Make a Handle
I used self-drilling screws and small washers to secure the carry handle (a piece of leather belt). This conveniently fits between the corner braces when folded down. The weight balance was quite good. I also used a bit of bungee cord to tie the legs together so they don't swing out when you pick up the bench.
Step 13: Folded Up Bench
Here's the bench all folded up.
Step 14: Ready for the Next Project
Here's the finished bench, laid out with the tools I used. I also used a compound saw (it appears in some of the other photos). I built the bench over a weekend, maybe about 6 hours total. Still to come is mounting a vice (which will be removable, using engineers bolts and wing-nuts again), and maybe a small drill press. I always wore my ear-muffs and safety glasses when using the power tools.