Things You'll Need
Instructions
Lay out four 4 by 4 boards, each 10 feet long. These will be the main supports for the swing set. In addition you will need to set out a 4 by 4 by 8 for the overhead cross piece and two additional sections of 4 by 4's which will hold the main supports together. These will be cut to length later and bolted into place.
Dig four holes 18 inches deep. In order to properly place each hole, dig them one at a time. When the first is dug, set a 4 by 4 by 10 into the hole. Angle the board at a 30 degree angle. Have someone hold this board in place while you position a second 4 by 4 to intersect with the top of the first board. The second board must also be set at a 30 degree angle. Dig your second hole where the board touches the ground. Repeat this process 9 feet to the side of the first pair of holes.
Drill a hole through both 4 by 4's. With the 4 by 4 by 10's positioned in the holes and set at 30 degree angles, drill a hole at the point where they intersect. The boards will be side by side with approximately 18 inches of board extending above the point where they intersect. Once the hole is drilled insert a 9 inch bolt and tighten it down until the nut digs slightly into the wood. Fill the holes with dirt, making certain the frame is level. Pack the dirt to firmly hold the frame in place. Repeat this to form 2 sets of frames 9 feet apart.
Measure the distance between the two angled 4 by 4's at 36 inches off the ground. Cut a 4 by 4 to match this length. Make the cuts at 30 degrees to match the uprights. Hold the board against the outside of the two upright pieces at a height of 36 inches, making certain it is level. Mount the board to the frame by drilling holes and inserting additional 9 inch bolts. When you are finished you should have what appears to be two large "A"s nine feet apart.
Lay the 10 foot 4 by 4 atop the two "A" frames. Where the uprights criss cross they create a "V" which will act as a craddle to hold the cross section. Center the board until you have the same amount of overhang on each side of the frame. Secure this cross section in place by drilling holes through the cross piece and "A" frame where they intersect. You will only need to put a bolt through one of the upright pieces to hold the cross section in place. Use additional 9 inch bolts, making certain they are tight. The basic frame is now complete and ready for the swings to be added.