How to Sharpen and Replace Chipper Blades
Tips for Chipper Blade Maintenance
I love wood chippers because of what they allow me to enjoy: A clean yard. A safe walking space free of large branches. Occasionally, some high-quality, low-cost mulch.
But I canít enjoy any of that if my wood chipperís blades are dull.
With a little bit of know-how, sharpening and changing your chipperís blades or knives can be easy as well as safe.
When Should I Sharpen?
Some manufacturers recommend sharpening or changing your chipper blades after every twenty-five hours of use. Others suggest sharpening chipper blades at least once a year.
I say that when your wood chips start to come out rough, uneven, and shredded, itís time to give your blades some attention.
As part of safe operation, you should always inspect your chipper blades and knives prior to each use. If they look worn or have chips or cracks, they need to be sharpened or changed.
Below are the steps you need to safely remove, sharpen, and replace your chipper blades and knives.
How to Remove Chipper Blades
Whether youíre sharpening your old chipper blades or putting on new ones, youíre going to have to remove the old blades from the†rotor assembly.
Keep in mind, the steps below are general guides. Itís always best to consult your chipperís product manual for specific details before you start.
Also, these steps are intended for consumer or prosumer-level chippers. Commercial-grade chippers are larger machines with additional features that might not match what you read in this guide.
Donít let the idea of big machines daunt you, though. Even though we recommend working with a partner, changing the blades on your consumer or prosumer chipper is as easy as a few simple steps.
- Personal protective equipment (PPE) - safety glasses, gloves
- Wrench/socket wrench
- Torque wrench
- Impact driver
- Sharpening tools if sharpening (sander, grinder, whetstone, file)
1. Safety First
Donít put yourself in danger! Unplug your electric chipperís power cord, or disconnect the spark plug in your gas chipper. Failing to do so can leave you at risk of the chipperís engine starting while youíre working.†
2. Remove the Top Hopper
If your machine is a chipper shredder, remove the hopper that feeds leaves into the shredder by loosening the bolts that hold it in place. This will allow you to access the chipper blades.
3. Remove the Housing
The housing is the protective metal case surrounding the rotor assembly and the blades. In our photo, you can see that we used a 13 mm socket wrench to loosen the nuts along the perimeter of the housing.†
Carefully lift the housing and set it aside so that you have access to the chipperís rotor assembly.†
4. Loosen the Bolts Securing the Blades
In many cases, chipper blades are attached to the rotor assembly with bolts that can be loosened using a hex key or Allen wrench.†
You might find that your bolts are tight or difficult to turn, or that theyíre held in place by a thread locker. In that case, you can attempt to get creative with your tools.†
However, a driver such as the Milwaukee driver we used, combined with an appropriately sized bit, is a more efficient way to get the torque you need. A breaker bar also would work, but not as quickly.
5. Remove the Blade
Even if it needs to be sharpened or replaced, your chipper blade still has a cutting edge that can slice through the skin. Make sure that you wear an appropriate set of safety gloves and that you grab the blade by its sides to catch it when you remove the bolts.†
How to Sharpen Chipper Blades
If thereís one thing to be said for certain about chipper blades, itís that frequent and proper inspection and sharpening are great for prolonging their life and saving yourself money in the long run.†
However, aside from making sure that you maintain the blade angle that the manufacturer recommends, there isnít one preferred way to sharpen them.
Consumers and professionals alike use all sorts of tools to hone their chipper blades. If you don't have any in your garage, a professional sharpening service will be able to sharpen your chipper blades for a nominal fee.
Here are some of the most commonly used tools used to sharpen chipper blades:
A disc sander is a tool that many consumer-level users might have in their garages. For sharpening chipper blades, a 100-grit sanding disc is recommended.
To use a disc sander, youíll need a vice to hold your blades in place while sharpening. Sharpen the blades by passing the disc sander over the beveled edges of the blades in quick, short strokes. Be sure to hold the sander steady and to match the angle of the bladesí bevel.
If you have dual-edged chipper blades, turn the blades around and repeat the process along the other cutting edge.
Wet Wheel Grinder
Like a disc sander, a wet wheel grinder or wet wheel sharpener is a tool that might be part of your setup in a consumer or prosumer garage. However, a wet wheel grinder has certain advantages over a disc sander:
- A whetstone made specifically for sharpening metal
- A water well that keeps the whetstone cool and helps prevent metal from being overheated
- A built-in vice or grip to hold blades in place
- A guide to help users set and maintain the sharpening angle
Even with those advantages, itís still recommended that users sharpen their chipper blades using quick, short pulses of the grinderís whetstone. This, along with the water from the grinderís well, will reduce the chances of the bladesí metal overheating and suffering damage.
Although belt sanders are more common in professional workspaces than in consumer garages, they work using a similar principle as the disc sanding technique.
The main difference is that the belt sander will be stationary, while the chipper blade will be the object that youíll have to hold steady.
To help with that steadiness, place the chipper blade in a chisel guide.
Hold the guide and the blade upside down so that the beveled surface of the blade is parallel to the sanding surface. With your belt sander running, touch the blade to the sanding surface with quick, short pulses.
How to Replace Chipper Blades
As helpful as it is to save money by sharpening chipper blades, eventually your blades will develop too many dings and dull spots for them to be sharpened to a clean, sharp edge.
Replacing your chipper blades is as easy as removing them in reverse, though these handy tips will help you get the most out of your blades when youíre putting them on:
- Replace all your blades or knives at once or in pairs whenever possible for balanced, even chipping
- If your chipper uses an outer pair of blades and an inner pair, and you have only one new pair of replacement blades, put the new, sharper blades on the outside of the rotor assembly and put the used blades in the best condition on the inside
- Before attaching new blades, check for debris wrapped around the shaft of the drum or rotor, or packed into the housing surrounding the drum, and remove what you find (note: there shouldn't be any blades in the machine while you're removing debris)
Bonus Tip: How to Prolong Sharpness
This suggestion comes from several professionals and can be done either before installing new chipper blades or after sharpening old ones.
To prolong the sharpness of your blade, secure the blade in a vice or a grip with the cutting edge pointing up. Lightly run a #10 flat coarse cut mill file, also known as a bastard file,†along the entire cutting edge, following the angle of the blade. Hold the file evenly with each pass to avoid creating a back bevel.
Although itís impossible to guarantee that doing this will extend the life of your chipper blade in every case, itís worth trying if you have the equipment at hand.
The Joy of Sharp Blades
Maintaining the blades on your wood chipper is important, not only because dull blades produce low-quality wood chips, but also because they force your engine to work harder, which leads to premature engine wear.
By using new or sharpened chipper blades, youíll keep your chipper in working condition for years to come, and youíll have that many more years of a clean yard and your own wood mulch to look forward to.
That makes you pretty sharp when it comes to cleaning up yard debris if I say so myself.