Sharpen while the blade still has its shape; replace when it has lost it. The edge is the cheap part to restore and the least important part of the blade.
The four conditions that end a blade
A worn lift wing. The upturned tail at each end of the blade is what moves air. It erodes — sand and grit scour it over seasons — and when it has thinned, the deck loses the lift that stands grass up and the flow that fills the catcher. No sharpening restores it, and this is the condition most people miss because they look at the edge.
A notch. A dent from a stone deeper than can be ground out leaves a weak point in a component spinning fast.
An elongated centre hole. The blade no longer sits concentric, and it will not balance at any grind.
Cracks, anywhere. The end of the blade, immediately.
What sharpening buys
A clean cut and the energy that goes with it, at the cost of an hour or a small workshop fee, plus a balance check that is not optional.
Over a blade’s life you might sharpen it two or three times before one of the four conditions above arrives. That is the realistic ratio on a domestic machine.
The economics on this shelf
A replacement blade for a common machine is inexpensive, which pushes the calculation toward replacing. Two things push back.
First, fit uncertainty. The aftermarket on this shelf is dominated by sellers who publish long compatibility lists, and a blade that is nearly right is worse than the old one.
Second, profile. The maker’s blade was the one the deck was tested with. An aftermarket blade of the same length can have a different wing and behave differently in the same housing.
How this site handles it
The blade family here prints the stated length, the fixing as the listing describes it, and the machine list as the seller’s claim. Where a blade is the machine maker’s own part, the page says so, because on this shelf that is the one piece of information that removes the fit question entirely.
The questions that keep coming in
Are the cheap aftermarket blades a bad idea?
They are a different article from the maker’s own, with a profile chosen by the seller. What matters is length, the centre fixing and whether the lift wing is the same shape, and the listings on this shelf state the first two and almost never the third.
Can I just fit a mulching blade to any mower?
It will bolt on if the length and fixing match. Whether the deck can use the different airflow it produces is a separate question, and a mulching profile in a deck designed for collection often collects worse.
Last reviewed 26 September 2026