6.4 No-Rot Picnic Table
Video: Picnic Table Project Overview
No-Rot Picnic Table
If you’re tired of wobbly all-wood picnic tables with legs that rot too soon, this project is for you. And if you’ve ever hesitated to sit at a picnic table because it looks unreliable, this simple design will improve your outdoor eating experience. The metal framework is strong, stable, solid and rot-proof, while the easily replaceable wooden top and seats make this one long-lasting picnic table.
As a welding project, this gives you practice making perfectly square corners with long pieces of metal. The video overview above introduces some tips you’ll use over and over again in welding.
|Part||Material||Size (thickness x width x length)||Qty|
|Bottom||⅛"-wall mild steel square tube||2" x 2" x 54"||2|
|Seat uprights||⅛"-wall mild steel square tube||2" x 2" x 13"||4|
|Table uprights||⅛"-wall mild steel square tube||2" x 2" x 26 ½"||2|
|Center rail||⅛"-wall mild steel square tube||2" x 2" x 66"||1|
|Table supports||⅛"-wall mild steel angle iron||2" x 2" x 40"||2|
|Seat supports||⅛"-wall mild steel angle iron||2" x 2" x 11"||4|
|Top boards||construction-grade lumber||1½" x 7 1/2" x 96"||6|
|Seat boards||construction-grade lumber||1½" x 7 1/2" x 96"||4|
|Lag bolts||⅜"-diameter x 1½"||20|
I like printing out the plans to bring to the workshop so I can follow the instructions more easily. This project is built using only two types of mild steel: 2" x 2" square tube, and 2"-wide x ⅛"-thick angle iron.
Start by cutting all parts to length following the dimensions in the materials list.
One aspect of this design that speeds construction is that no parts need to fit between other parts. This means you don’t need to cut and fit a part to fit a specific space; you can just cut the parts according to the materials list and put them together as shown in the plans. It’s a forgiving design.
In many other projects, though, you’ll get better results if you cut to fit, rather than just follow a materials list. When a part needs to fit tightly in a gap, measure the gap carefully before cutting. This way, you’ll adjust as you go for slight deviations in materials or inevitable human error.
A metal-cutting chop saw is the ideal tool for preparing parts for this project because it’s fast and accurate. After you’ve cut all the parts to length, trim the corners of the angle iron to 45º (and grind off any sharp edges) for good looks and safety. If you leave the ends square and sharp, there’s a good chance someone sliding down the seat will cut their calves. Ouch!
Bore holes for lag bolts in the top faces of the seat supports and table supports. Since the lag bolts are ⅜" in diameter, make the holes 1/32" or 1/16" larger than the bolts.
Weld the end frames
Begin assembly by welding the two end frames together. You can use the factory edge of a plywood sheet as an accurate, reliable reference for 90º assemblies. Plywood sheets, at least the ones I’ve seen in North America, are remarkably square. You could also use a 24" carpenter’s square.
Start work by welding two seat uprights to each bottom piece. Do this work with the uprights lying on a flat floor. The plans show how the bottom ends of the seat uprights rest on the top edge of the bottom pieces. Complete each end frame by adding one table upright to each bottom member. Leave the seat supports and table supports for now.
TECH TIP: Practice each welding joint
Even skilled welders weld sample joints before starting the welds on a project. Weld quality is the reason why. Different joint situations and metal thicknesses call for different voltage and wire feed settings. Different joint situations are also best welded in different orientations. Practice welds give you the chance to make mistakes, and fix them, on scrap metal.
This picnic table includes two different weld configurations: square-tube-to-square-tube; and angle iron-to-square-tube. Assemble some scraps of 2" square tube and 2" angle iron into mockups of these joints, then try your best to lay down a strong, attractive weld bead.
Square tube of the kind we’re using here has a ⅛"-thick wall that’s fairly easy to weld. That said, too hot an arc can burn through and leave an unsightly hole. Practice on scrap until you can reliably and attractively weld this kind of square tube. Don’t attempt to weld your project until you can reliably complete your mockup welds.
As with all welding, horizontal joints are easier to weld than vertical ones. In vertical welds the tendency is for the molten weld pool to drip down, making for an unattractive weld. While it’s certainly possible to produce a good weld in a vertical orientation, horizontal is easier and better whenever you have the option of laying your parts down flat.
Connect the frames
With the two end frames assembled, get ready to connect them with the center rail. Sounds simple, but there are some tricks you can use to avoid hidden pitfalls. The main issue is ensuring that both end frames are in the same orientation as each other so they come together square and accurately. A 6" magnetic level is the ideal tool for this. In fact, a level is the best tool for orienting parts properly in all kinds of metal projects.
Place each frame upright, spaced 66" apart (the length of the center rail), on a flat working surface such as a concrete garage floor. You can attach a big C-clamp or two on each bottom member as a temporary foot to keep each frame from toppling over – or enlist a helper to give you an extra set of hands.
To orient these frames so they’re parallel to each other, cut two scrap 2x4s to exactly the same length as the center rail. Place one 2x4 spacer between the frames at one end of the bottom pieces, and another at the other end. Pull the frame tight to the ends of the 2x4s with a couple of pipe clamps and they’ll be parallel. If you don’t have pipe clamps, you can improvise with other clamps and extra wood.
Next, put a straight piece of wood extending from the top of one bottom member to the top of the other, then put a level on the wood. If your work floor and the two frames are not level, use shims to raise whichever end of the bottom members is low. The ultimate goal is that both frames are level, parallel, and aligned squarely with each other. Any wonkiness between the two end frames will become permanent after welding, so be sure to get things right.
Support the center rail at the correct height on some 11" wood props. Use a pipe clamp or some rope to pull the two frames tightly towards each other, resting against the ends of the center rail and the ends of the 2x4s. Use your level again to check and adjust the end frames so they’re plumb (standing straight up and down). If the two frames are both level with each other, and both frames are also plumb, then you’re all set to join them together accurately with the center rail.
Use the level again to orient the table supports and seat supports before clamping them in place. As long as the bottom members are level, the seat and table supports will be parallel if they’re level, too. Tweak, clamp, tack weld, remove the clamps, then final-weld all the angle iron parts.
You can paint the metal frame to keep rust at bay, but only after you’ve removed mill scale and oils from the steel. Bolt your tabletop and seat boards to the metal frame with lag bolts, then fire up the barbecue for lunch in the sun.
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