Sharpen tree pruning shears by removing the retaining bolt that hinges the two blades using a flat file and following the curved bevel on the cutting blade and using a curved file to maintain a crisp 90-degree angle on the blunt edge blade. Check the blade for burrs and remove them using sandpaper.
This type of pruning shear is one of the most difficult to sharpen due to the curved blades. Use a vice to hold the tool steady when sharpening it. Make gentle strokes with the file and maintain the factory bevel by checking after each stroke. The goal of sharpening is exposing fresh metal along the entire curve.
If you find burrs on the back of the blade after sharpening, tape a sheet of 300-grit sandpaper to a workbench with the abrasive side on top. Keep the blade flat against the sandpaper and move it in a small circular pattern to remove the burrs.
Sharpen the blunt cutting blade using a 10-inch half-round file. Because it is critical to maintain the angle, use both hands to control the file. Use the sandpaper technique to remove burrs from both sides of this blade. Reassemble the shears and lubricate the pivot point with a drop of oil. The sharp sheers enable cutting branches up to 1 inch in diameter.