While many toppers use flails or discs, there are still a few models knocking around where blades are tasked with the cutting. As you can see from the pictures, this is a small topper that features three blades working across a cutting width of six feet.
The key things to watch out for when blades start to get dull and lose their cutting edge is that the grass will start to look 'torn' rather than cut cleanly. This has a couple of implications, the most important of which is that regrowth of the grass can be slower.
When you think about it, one of the main roles of topping is to encourage good quality grass regrowth, so this is a major reason to keep on top of dull blades. The other reason to keep blades sharpened is they will use less power (and therefore diesel) when they are properly edged or replaced.
The blades pictured here needed complete replacing. They owed us nothing and had approximately 200 hours of cutting done. They had been sharpened a few times already, but the best thing to do this time was replace them entirely. How do you know when it is better to replace rather than edge them again? If the blades are worn out, unbalanced, too narrow to edge, or with chips or chunks gone out of the metal, it's wise to get a new set.
When taking the blades off, a good tip before you start is to mark each blade to make sure it goes back on the correct way. There is a method in the way blades are placed and the direction cut grass is thrown in will be impeded if the blades are put back on in their incorrect positions. A quick pointer on the deck with a marker will save a lot of hassle.
If the blades are worn back beyond the point of sharpening - as in this case - it is better to replace them. Be sure to only use the correct blades as recommended by the manufacturer. A new set of three blades here set us back around €180. It's a good idea to wear thick gloves when doing this job to keep your hands safe.
You can jam a small piece of wood between the blade and the deck to keep things from turning while you are removing the blade mounting bolt. Use a socket wrench of the appropriate size and unbolt the mounting, while using your other hand to keep the blade from turning.
Be careful not to lose the mounting nut or washer that holds the blade in place. Pay attention to the position of the blade as you're removing it and mount the new one in the same orientation.
Line up the new blades as they were lined up before and reinstall the mounting gear. Make sure not to over-tighten and warp the blade, which can cause vibrations when topping. Finally, make sure there is clearance from each blade to the deck. Sometimes a new, longer blade will be within touching distance of the deck if it's frame has been damaged in the past - you will hear this as soon as you start working!
If you think there is enough left in them for another season, it is acceptable to re-edge the blades. The easiest thing to do is take them off and edge them using a grinder. Secure each blade in a vice and edge them one at a time. Run the grinder side to side along the bevelled edge of the blade. Keep the grinder moving constantly so you don't file down one part of the blade more than the rest. Continue filing the edge until you see clean, bare metal along the entire blade and the edge is sharp. Make sure to wear proper eye protection and beware of stray sparks.