Backyard swing sets are popular among parents who want to provide their children with playground fun at home. While a variety of wood, metal and plastic swing sets are available on the market, sturdy swing sets can be expensive and some parents decide to build their own. A-frame swing sets are simple to build and very sturdy once in place. When building an A-frame swing set, it is important to plan the structure to conform to your landscape and to place the posts no more than 10 feet apart, to keep the swing set from sagging.
Cut a 12-degree angle into the tops of four of the 4-inch by 4-inch posts using the mitre box. Set the angled ends of two posts together to create a V shape, then outline a 4-inch by 6-inch box at the top of the joint. This box is where the top rail will be set on to the A-frame. Cut out the box and use the two cut-out pieces (one from each post) as a template to make the same cuts on the other two posts.
Cut cross braces for each A-frame. One cross brace should be near the top of the frame and the other just above the midpoint. Measure the length needed for each cross brace, then cut them to size with a 12-degree angle at each end. When measuring for the cross braces, remember that the bottom 18 inches of each post will be buried.
Assemble the A-frames. Clamp the posts together with the cross braces in place. Nail the cross braces to the posts.
Measure the distance between the posts and dig the post holes. Each hole should be 12 inches in diameter and 18 inches deep. Set the posts into the holes.
Bolt the legs together using A-bar metal swing set brackets. Set the top rail in place and check that the swing set is level.
Mix the concrete directly in the holes. Follow manufacturer instructions to ensure your water to concrete mix ratio is exact.
Drill holes through the sides of the A-frame posts into the cross braces and top rail. Insert screws and secure them tightly.
Attach swings and toys to the top rail. Space the swings according to manufacturer instructions and install them as directed.
Allowing the top rail to extend beyond the posts will give you more room for swings or other hanging toys.