Short answer: There is no one schedule that fits every robot mower. How often you replace blades depends on your grass, how long your mowing season is, and what the maker advises, so check the manual. A good habit is to look at the blades regularly and replace them when they are worn, bent or chipped, and always as a full set.

What are robot mower blades?

Most robot mowers use blades that are typically small and light, much smaller than the blade on a push mower. Many are thin pieces of metal that swing freely on a pivot, so they can fold back if they hit something hard. They are held by a screw to a spinning disc under the mower.

Small blades cut a little at a time. That is why robot mowers mow often and leave very short clippings. If you want to understand where this fits in the bigger picture, see how robot mowers compare to push and riding mowers.

Some models use other cutting parts, such as fixed blades or different types of cutting systems. The details differ by maker, so your manual is the right source for your model.

Why do the blades wear out?

Blades work every time the mower runs, and robot mowers run often. Over time the edges get dull. A few things speed that up:

  • Hitting hard objects. Stones, roots, sticks and edging can nick or bend a blade.
  • Sandy or dry soil. Dust and grit rub away at metal.
  • Long mowing seasons. More hours of running means more wear.
  • Tough or wet grass. Dense, coarse or very wet grass can load the blades more.

How do I know the blades are worn?

You can often tell without taking the mower apart, but the clearest check is to look at the blades directly. Common signs:

  • Ragged or brownish grass tips. A dull blade tears grass rather than slicing it.
  • More vibration or noise than before. A bent or damaged blade can throw off balance.
  • Visible damage. Chips, bends, cracks, or edges that look rounded and thin.
  • A mower that seems to struggle on grass it used to handle. This can have other causes too, so check the rest of the underside as well.

These are general signs, not tests of any one model.

How often should I replace them?

We do not have an interval to give you, and any fixed number would be a guess. Makers publish their own advice, and it varies. Your own use matters more:

  • A small, tidy lawn with soft soil may be easy on blades.
  • A large lawn, a long season, sandy ground or lots of small obstacles can wear them faster.

A practical approach:

  1. Check the manual for the maker's advice on your model.
  2. Inspect the blades regularly. Many owners look at them at the same time as they clean the underside. The maintenance checklist puts this in a routine.
  3. Replace when worn, bent or chipped. Do not wait for them to break.
  4. Replace the whole set at once. Mixing new and old blades can unbalance the cutting disc.
  5. Use blades made for your mower. Check the manual or ask the maker for the correct part.

Cost is not quoted here, because prices vary by maker and change often. The cost article lists blades among the other expenses to plan for.

How do I change the blades?

The exact steps depend on your model, so follow the manual. In general it goes like this:

  1. Switch the mower off. Use the power or stop control as the manual describes. Some models also have a lockout or PIN. Do not work on a mower that might start.
  2. Wear thick gloves. Even small blades are sharp.
  3. Turn the mower over on a soft surface, the way the manual shows.
  4. Undo the screw holding the blade or blade holder.
  5. Remove the old blade and look at the disc and the screw for damage or tangled grass.
  6. Fit the new blade or set, make sure it can move freely if it is a swinging type, and tighten the screw as the manual says.
  7. Check the work. Spin the disc by hand, if the manual allows, to make sure nothing rubs. Put the mower back the right way up.

Because the blades are the part that can hurt, keep children and pets away while you work. For more on that topic, see our article on whether robot mowers are safe for kids and pets.

What this means for you

Blades are a small, regular cost. Look at them often, replace them when they show wear, and follow the manual rather than a fixed calendar. A quick check is cheaper than cutting poorly for weeks.

For the details-minded

  • Swinging blades are generally designed to pivot out of the way on impact. That reduces breakage but does not stop them from dulling.
  • Blade material, thickness and fastener type vary by maker. Do not swap parts between brands unless the maker says it is safe.
  • Some makers sell blade sets sized and balanced for particular models. Use those.

Next step

Choosing a mower and want to know what upkeep to expect? Try our quiz at /help-me-choose/.

Quick answers

Should I sharpen the blades instead? Check the manual. Many makers design these blades to be replaced rather than sharpened, because they are small and thin.

Can I replace just one blade? It is better to replace the whole set. Uneven blades can cause vibration.

Do I need to turn the mower off first? Yes. Always switch it off before touching the blades, and wear gloves.

What if the blade keeps bending? Look for stones, roots or edging in the mowing area. If it keeps happening, check the manual or contact the maker.