Build the A-frame ends first.
The swing set has become an icon of the British back garden. You can spend hundreds or thousands of pounds on these structures that now include forts, slides, see-saw, gliders and more. For some, these prices are out of reach. Others would simply rather build their own out of common materials and save their money for more important things. This simple swing set is easy to build and easy on the budget.
Child safety first: round the edges and ends of all pieces of timber with a belt sander. Use 9 mm (3/8 inch) carriage bolts for fasteners and countersink the holes on the threaded side, so that no bolts protrude from the frame. Construct the A-frame ends from 2.4 or 3 m (8 or 10 foot long, 10 by 10 cm (4 by 4 inch) pressure-treated posts. The two posts meet at an angle of 60 degrees. To accommodate a cross beam between end frames, cut the post top ends at 30 degrees. Cut the post bottom ends at 60 degrees to sit flat on the ground. See the illustration. Use a rafter square to mark the angles. You are making an equilateral triangle in which the base is the same as the height. To use 8-foot long posts, make the base 2.1 m (7 feet) wide and the finished height will be about 2.1 m (7 feet). Cut the posts on a mitre saw. For the bottom ends of the posts, you will have to cut complementary angles since the maximum angle on a mitre saw is 45 degrees. Add two 5 by 10 cm (2 by 4 inch) cross pieces, one at the apex where the angle cuts end and the other at a height of 105 cm (3 1/2 feet) from the bottom of the A-frame. The opening for the swing support beam should be 105 cm (3 1/2 feet) wide or slightly more--measure the beam for the opening size. Drill holes for 9 mm (3/8 inch) carriage bolts and countersink the holes on one side so that the bolt ends, washers and nuts are below the surface of the wood. Trim the ends of the cross pieces to match the 60-degree angle of the A-frame.
Stand the A-frames up in place and temporarily brace each with two 2.5 by 7.5 cm (1 by 3 inch) boards. Plumb the frames with a level. Lift a 10 by 15 cm (4 by 6 inch) beam (get a helper, they are heavy) into place between the two frames. Secure with two 1.2 cm (1/2 inch) bolts by drilling through the post, into the beam and out the other post. Countersink the holes to hide the nuts, washers and bolt ends. Make swings seats from 3 by 15 cm (5/4 by 6 inch) deck boards. Drill two holes in each end for ropes. A good width is 30 to 35 cm (12 to 14 inches). In the swing support beam, drill 9 mm (3/8 inch) holes and install 9 mm (3/8 inch) eye-bolts. Countersink the holes on top of the beam to hide the nuts, washers and eye-bolt ends. Suspend the swings with soft, 1.5 cm (5/8 inch) braided rope. Synthetic rope is best since it doesn't rot. Thread the rope through an eye-bolt and take both ends down through one end of the swing seat, one rope end through each hole. Tie a knot and secure the tag ends of the knot with waterproof duct tape.
Dig post holes 15 cm (6 inches) in diameter and 60 cm (2 feet) deep next to each post. Set a pressure-treated 5 by 10 cm (2 by 4 inch) upright in the hole and bolt it to the 16 by 16 cm (4 by 4 inch) frame post. Counter sink the nut and bolt end into the 16 by 16 cm (4 by 4 inch). Add half a 18 kg (40 lb) bag of quick setting concrete to the hole and stir in water per instructions. Once the concrete sets, typically after 30 to 60 minutes, refill the remainder of the hole with soil.
- "Modern Woodworking"; Willis H. Wagner; 1967