# How to sharpen or replace mower blades

Source: https://mowandedge.co.uk/blog/how-to-sharpen-or-replace-mower-blades
Published: 2026-10-12
Publisher: Mow and Edge

**In short:** Yes, you can sharpen a rotary mower blade if it is dull or lightly nicked, as long as you keep the original angle and balance it afterwards. Replace it if it is bent, cracked or badly worn. Robot mower razor blades are not sharpened: makers sell them as cheap replacement sets, and you swap the whole set, often with new screws, when they look worn.

A sharp blade cuts grass cleanly. A dull one tears it, leaving ragged brown tips, and makes a cordless mower work harder and drain its battery faster. Sharpening or replacing a blade is a straightforward job if you take safety seriously and follow your manual. This guide covers both rotary blades on cordless push mowers and the small pivoting razor blades on robot mowers: when to act, how to sharpen and balance, and which way round blades go back on.

## Signs your blade needs attention

As a rough habit, check a push mower blade at the start of each season and after hitting a stone or root. Many owners sharpen once or twice a season. Robot mowers cut every day, so their blades wear much faster.

- Grass tips look torn, frayed or turn brown a day or two after mowing.
- The mower leaves uneven strips or tufts on a flat lawn.
- Battery run time has dropped although the pack is healthy.
- The mower vibrates more than usual, which can mean a bent or unbalanced blade.
- Visible nicks, dents or a rounded cutting edge.
- On a robot, blades look blunt, chipped or no longer pivot freely.

## Removing a rotary blade safely

Blade fixings vary. Some cordless mowers use a single centre bolt, some a plastic blade holder, and some have a reverse thread. Your manual shows the method and any special tool. If you cannot find it, the maker's website usually has the manual as a download.

Tip the mower on its side with the air vents and battery bay facing up, never onto the motor housing in a way the manual warns against. Mark the underside of the blade with a pen before removal so you know which face goes back down.

1. Remove the battery or safety key and wait for the blade to stop.
2. Put on sturdy gloves and eye protection.
3. Tip the mower as the manual shows and wedge the blade with a block of wood.
4. Undo the fixing in the direction the manual gives, keeping any washers in order.
5. Lift the blade off and note which side faced the ground.

Note: Before you touch a blade, remove the battery or safety key and wait for the blade to stop completely. Wear sturdy gloves and eye protection, and keep children and pets away while you work. If a blade is bent, cracked or you are unsure, take it to a dealer or sharpening service.

## Sharpening and balancing a rotary blade

Clamp the blade in a vice. Use a flat metal file along the original bevel, filing in one direction from the inside towards the tip. Aim to restore the edge, not to make it razor sharp: a slightly blunt, strong edge lasts longer on a lawn. Take the same number of strokes on each end so they lose a similar amount of metal.

Balance matters as much as sharpness. An unbalanced blade vibrates, which wears the motor bearings. Hang the blade on a nail or a cheap cone blade balancer. If one end drops, file a little more from that end, away from the cutting edge, until it sits level.

If the blade is bent, cracked, worn thin or the nicks are deep, do not try to straighten it. Fit a new one from the maker. A local mower dealer or sharpening service can also sharpen and balance blades for you if you would rather not do it yourself.

| Condition | Action |
| --- | --- |
| Dull edge, small nicks | Sharpen and balance |
| Deep nicks or chips | Replace, or ask a sharpening service |
| Bent, cracked or thin | Replace with the maker's part |
| Robot razor blades worn | Replace the full set |

Sharpen or replace?

## Which way round the blade goes

On most rotary blades the sharpened edges lead in the direction of rotation and the raised wings or sail at the back of each end face up towards the deck. Those wings create the airflow that lifts grass and throws clippings into the box. Fitted upside down, the blade cuts badly and collects poorly.

Use your pen mark, check the manual's diagram, then tighten the fixing to the torque or method the manual states. Spin the blade by hand, wearing gloves and with the battery still out, to check it turns freely without touching the deck.

## Robot mower razor blades

Many robot mowers, including Husqvarna Automower and Gardena Sileno models, use small pivoting razor blades on a disc. Others, such as some Worx Landroid models, use a different blade design. Because they cut little and often, the blades are thin and are meant to be replaced, not sharpened.

How often depends on lawn size, grass type and how much debris the mower meets. Many owners swap blades every month or two during the season, and sooner on lawns with twigs, cones or gravel edges. Husqvarna and other makers give a recommended interval in the manual. Replace all blades on the disc at once, with the screws the maker supplies, so the disc stays balanced. Our [robot lawn mower guide](https://mowandedge.co.uk/best/best-robot-lawn-mower) and [Husqvarna Automower comparison](https://mowandedge.co.uk/best/husqvarna-automower-models-compared) cover models and their cutting systems.

For push mowers, a sharp blade pairs well with the right cut height. See [lawn mower height settings](https://mowandedge.co.uk/blog/lawn-mower-height-settings), and if you are replacing the whole mower, our [cordless lawn mower guide](https://mowandedge.co.uk/best/best-cordless-lawn-mower).

1. Switch the robot off as the manual describes and wear gloves.
2. Turn it over onto a soft surface.
3. Remove each blade screw with the right screwdriver.
4. Fit new blades and new screws, checking each blade pivots freely.
5. Clean grass build up from the disc and skid plate before you turn it back over.

## Frequently asked questions

**Can you sharpen lawn mower blades yourself?** Yes, rotary blades can be sharpened at home with a file and a vice, then balanced. Remove the battery first, wear gloves and eye protection, and replace any blade that is bent or cracked.

**Is a lawn mower blade sharpener worth buying?** Drill mounted sharpeners and files both work. A simple file and a blade balancer are enough for most home users. If you are unsure, a dealer or sharpening service is a safe option.

**How often should Husqvarna Automower blades be changed?** Husqvarna gives a recommended interval in each manual, and wear depends on your lawn. Check the blades regularly and replace the full set when they look dull or damaged.

**Can I sharpen robot mower blades?** It is not recommended. They are thin, low cost parts designed to be swapped as a set with new screws to keep the disc balanced.

## Buying guides on this topic

- https://mowandedge.co.uk/best/best-cordless-lawn-mower
- https://mowandedge.co.uk/best/best-robot-lawn-mower
- https://mowandedge.co.uk/best/husqvarna-automower-models-compared

## Sources

- [RHS lawn care](https://www.rhs.org.uk/lawns)