Maintenance (excluding the power plant) Your primary maintenance concern with chippers and shredders is their knives. You can re-sharpen chipper knives, whereas you can reverse shredder flail-type knives when dull but you can not re-sharpen them. You must sharpen chipper knives with special sharpening equipment because they are made of high-carbon steel. Maintaining sharp knives can lengthen their life and the life of the machine by keeping power requirements low. An over-dulled or chipped chipper knife will need extensive sharpening, which will remove a large portion of the blade. This obviously will shorten its life. As soon as a blade is slightly dull, you should sharpen it to minimize the amount of blade-material that you remove. All knives need sharpening at the same time to keep them in balance-even if only one is worn or chipped. Also, you must use matched sets to keep the knife the same distance from the anvil for proper chipping and feeding. After removing the knives, clean the area where they are fastened with a wire brush to make sure they will align correctly. Be sure to torque the knife bolts to their proper specifications. You will need to examine the anvil and be sure it maintains a good, square edge. Occasionally, you may need to remove and sharpen it.