If your post hole digger tool no longer goes as deep or cuts the soil as easily as it did when it was new, it is probably time to sharpen the blades. You should keep the blades of all your hand tools sharp so that they work more efficiently and last longer. Sharpening the blades on a pair of post hole diggers is an easy task, and this simple how-to guide will show what to do. Let's get started.
Step 1 - Disassemble the Post Hole Diggers
Before you begin, you should disassemble the post hole diggers. Because the blades on a pair of post hole diggers don't open very wide, you will find it much easier to sharpen the blades if you disassemble the unit. To do this, take a pair of pliers and loosen the wing-nut on the side of the tool. Once the wing-nut is loosened, use your hand to remove the wing-nut and set it aside. Then, push out the bolt which holds the two blades together.
Step 2 - Clamp First Piece
Take one piece of the post hole diggers and clamp it down into device. Clamp the the tool so that the blade looks like an arc when you look at it from the front. In other words, it should look like an upside down "U".
Step 3 - Clean the Blade
Before you sharpen the blade, take a high-pressure spray nozzle and water hose and spray away any dirt or grime that may be on the blade. Then, allow the blade to dry. Take a wire brush and scrape the edges of the blade so that is free from any debris or obstructions.
Step 4 - Grind Damaged Areas
If the blade is damaged in any area, or has deep chips or dents, you can use an angle grinder with a medium grit wheel to take care of this.
Step 5 - File Sharp Edge
Once you have prepared the blade, take the sharpening file and begin filing the blade. Hold the file at a 45 degree angle and slide the file back and forth in a front to rear motion. Continue doing this across the entire surface of the blade. From time to time, take a look at the blade and make sure that the outermost part of the blade has a sharp 45 degree angle.
Step 6 - Remove File Burr
Once you have created the angle on the blade, there will be some file burr. Basically this is a result of uneven strokes and is to be expected. To remove it, lay the file flat on top of the bevel of the angle and give the file a couple of quick strokes. This will remove the burr.
Step 7 - Repeat for Other Blade
Remove the first piece of the the tool from the vise, and insert the second blade into the clamp. Repeat the process for the second blade.
Step 8 - Wipe with Penetrating Oil
Once you finish sharpening the blades, take an old towel and wipe some penetrating oil over the surface of the two blades. This will help prevent rust and corrosion, and also help create a nonstick surface for dirt and soil when using the tool.
Step 9 - Re-Assemble Post Hole Diggers
Line up the 2 pieces of the tool and reinsert the bolt. Then, twist on the wing-nut and tighten about a half turn past hand-tight with the pliers.