help me salvage my newish lawnmower.

Factual Questions
21

Sharpening the blade is not a big chore.

  1. Pull the plug wire for safety.
  2. Use a wooden chock and a wrench to remove the blade. (Sounds like the OP has already done this before).
  3. Clamp the blade in a vise or to a sturdy surface using vice-grips.
  4. Use a long mill bastard file to shape a new, even edge on each cutting blade. You want to preserve the existing angle if you can, as it’s likely the optimum between cutting and wear resistance.
  5. Remount the blade - ensure it’s locked in place and the bolt is tight.

If you do it frequently enough, you can do touch-up sharpening without removing the blade. Never forget to pull the plug wire before doing ANYTHING under the deck.

22

Not so much cut as bludgeon. Years ago, many rotary mowers had blades made from flat stock and the back edge was not that much different from a never sharpened cutting edge. Only ever saw homeowner blades that dull. Did see some blades put on backwards/upside down by new hires but it was always quickly discovered by the mess it left.