Do your lawn a favor by replacing the blade or blades on your rotary mower before the turf stirs in a week or two. A sharp blade makes clean cuts on fast-growing spring grass. Make a note of the configuration of the old blade before removing it, and note the sequence of washers. Socket wrenches make quick work of the job, but wear sturdy gloves when handling the blades. Tighten nuts to the manufacturer’s specifications. Test the mower to make sure the blade is centered.