How to Build a Posthole Digger
Fence posts must be driven deep into the ground so they are stable and cannot get carried off by wind or rain. A posthole digger allows you to dig a hole that is deep but not wide with straight edges, so you do not disrupt the surrounding soil. A posthole digger is basically composed of two shovels hinged together that you can drive straight into the ground and pull straight out to remove dirt. If you will only be installing one fence, you can make your own posthole digger rather than buying one that you'll use only once.
Cut two 60-inch lengths of the 3/4-inch electrical metal tubing. Measure 8 1/2 inches from the end of each and mark. From the same end measure and mark 20 1/2 inches, 47 1/2 inches and 53 1/2 inches. Use the conduit bender to bend each piece to a 35-degree angle at the 8 1/2 mark. Bend the 20 1/2 mark to a 35-degree angle in the opposite direction to form an "S' shape. Bend the 47 1/2 mark in the same direction as the 8 1/2, and the 53 1/2 mark in the same direction as the 20 1/2.
Assemble your handles. The length of pipe above the 8 1/2-inch mark are your handles. Snuggly fit a bicycle grip over each pipe.
Make your spades. Cut the 4-inch electrical metal tubing in half so you have two 3 1/2-inch pieces. Cut each pipe vertically open in a straight line and use the conduit bender to open each pipe into a semicircle. Draw a rounded edge around the bottom of each piece and use your saw to cut along it. Cut four small triangles into the bottom of each piece to form teeth.
Drill a hole half way between the 47 1/2 inch bend and the 53 1/2 inch bend in each pipe. Use your 5/16 machine bolt to connect the two pipes together so that they face each other symmetrically.
Attach the spades. Drill two holes vertically in the top of the spades 1 1/2 inch apart and drill corresponding holes into the bottom of your pipes. Join each spade to its pipe using the carriage bolts so that they are facing each other.
- Fence and shadow of fence on snowy ground.. image by LiteWave from Fotolia.com