What is backlapping, and why does it work?
Backlapping sharpens a reel mower by grinding the reel blades against their own bed knife with an abrasive paste, so the two surfaces mate perfectly. It works because a reel cuts by shearing grass between the spinning blades and the fixed bar — keeping those two edges matched matters more than making them razor-sharp on their own.Most manual reels have a backlapping port or simply let you turn the reel by hand or with a drill-driven kit. The compound does the cutting; you supply the motion.
How do you backlap a reel mower step by step?
Work methodically, and keep your hands clear of the reel while it moves.- Disconnect any power and, on powered reels, remove the battery or spark-plug lead before touching the blades.
- Adjust the bed knife so it just contacts the reel across its full width — it should lightly touch the blades.
- Brush lapping compound onto the reel blades with a stick or brush, never your fingers.
- Turn the reel backward (the reverse of the mowing direction), using the backlapping tool, hand crank, or a drill on the drive, so the compound laps the edges.
- Keep turning until the edges look bright and even, adding compound as needed.
- Wipe off all compound, then test on a strip of paper held to the bed knife — a clean reel slices it cleanly along the full width.
When is backlapping not enough?
Backlapping restores an edge but cannot fix a reel that is nicked, bent, or badly worn. If blades are gouged from hitting stones, or the reel no longer cuts paper after lapping, it needs machine grinding at a mower shop or a new reel. Check the bed-knife adjustment first, though — a mis-set bed knife mimics dullness. Reviewers consistently find most home reels need only a seasonal backlap, so try that before assuming the worst.What tools and compound do you need to backlap?
You need three things to backlap a reel: a lapping (valve-grinding) compound as the abrasive, a stick or brush to apply it, and a way to turn the reel backward, whether the mower's own handle, a hand crank, or a cordless drill fitted to the drive. A branded kit bundles these but is optional.Most hardware and auto-parts stores sell valve-grinding compound in a small tube for a few dollars, and one tube lasts many seasons. A medium grit suits general sharpening, while a finer grit gives a smoother final edge. You will also want gloves, a rag to wipe off the used compound, and a strip of newspaper for the cut test. If you plan to drive the reel with a drill, check that your mower has a hex or square drive point the chuck can grip, and run the drill slowly and in the correct reverse direction so the compound laps the edges rather than merely polishing them.
How often should you repeat backlapping?
Most home reels need backlapping about once a season, but let performance decide rather than the calendar. Sharpen again whenever the reel starts folding or tearing grass instead of slicing it, or when it stops cutting a sheet of paper cleanly along the bed knife.How fast the edge dulls depends on how much you mow, how gritty your soil is, and how tough the grass is; sandy or dusty lawns wear a reel faster than clean, fine turf. A quick paper-cut test every few weeks in the growing season catches dullness early, while it is still a ten-minute lap rather than a shop grind. Keeping the bed knife correctly adjusted between laps also stretches the interval, since a reel run too tight against the bed knife wears its edge much faster than one set to just kiss it.
