Garden shears are designed to make clean, precise cuts that promote plant health and minimize the risk of disease or pest entry. A dull blade crushes and tears plant tissue, leaving a slower-healing wound that makes the plant vulnerable to infection. Maintaining a sharp edge also significantly reduces the physical effort required, making the task easier and more efficient. Sharpening your shears with a hand file is a simple, low-cost method that restores the cutting ability of the steel blade, ensuring the tool slices smoothly through stems.
Preparing the Shears and Selecting the File
Before sharpening, the shears must be prepared, often requiring disassembly to access the cutting blade fully. Cleaning is essential, as sap, rust, and debris can damage the file and obscure the blade’s geometry. Use a solvent like mineral spirits or a dedicated resin remover, along with steel wool, to thoroughly scrub away any hardened material on the blade surfaces.
Once cleaned and dried, secure the blade, ideally clamped firmly in a vise, with the beveled edge facing upward. The most effective tool is a mill bastard file, designed for general-purpose sharpening of steel edges. A 10-inch or 12-inch length is manageable for most shears, and the “bastard cut” offers a good balance of material removal without being overly aggressive.
Filing Technique for the Cutting Edge
When sharpening, precisely follow the factory angle, or bevel, of the blade, which is generally 10 to 20 degrees for most garden shears. Examine the blade to identify this existing angle, as maintaining it is essential for creating a sharp, functional edge. If the original angle is lost or heavily damaged, use a general-purpose angle around 40 degrees.
The file must be pushed only in one direction—away from your body and across the bevel—in a long, smooth stroke from the pivot point to the tip. Never pull the file back along the metal, as this dulls the file’s cutting teeth and can create a weak edge. Maintain the file flat against the bevel, following the established angle to remove metal evenly and expose clean, shiny material along the entire edge.
Continue this one-directional filing process, using steady pressure, until a slight ridge of metal, known as a burr, forms on the back, or flat, side of the blade. This burr indicates that you have successfully filed all the way through the edge. For a well-maintained blade, achieving this result may only take about six to ten strokes. Once the burr is felt along the entire length, the sharpening of the bevel is complete.
Finishing the Edge and Reassembly
The burr that forms on the flat side of the blade must be removed to achieve a clean edge. To remove it, lay the blade flat side up and use a single, extremely light stroke of the file or a fine sharpening stone along the flat surface. This action should not create a new bevel but simply slice off the raised metal ridge, restoring the blade’s flat back.
After the burr is removed, the newly exposed steel surfaces should be protected from rust and corrosion. Wipe down the blades with a clean rag and apply a thin coat of machine oil, mineral oil, or a specialized tool lubricant to all metal components. Pay particular attention to the pivot point, applying a drop of oil to ensure the mechanism operates smoothly and prevents binding.
Reassemble the shears, ensuring all bolts and nuts are correctly tightened to hold the blades in proper alignment. A final test involves cutting a small piece of paper or a thin, dry branch; a properly sharpened shear will slice through the material cleanly without crushing or tearing it. Regular cleaning and oiling after use will help maintain the newly sharpened edge and extend the tool’s lifespan.