Blade Maintenance & Replacement Guide

Welcome to Arbgear’s guide to correctly and safely replace the blades in your Forst wood chipper. This guide will help you determine when your blades are "blunt" and require replacing to reduce unnecessary wear on your machine. It will also take you through the correct steps on removing and fitting the Forst blades in a safe manner.

Every operator will have a different opinion on how blunt their chipping blades can become before they need replacing. The problem with chipping with dull blades is that it causes unnecessary wear and stress to other components on the machine such as anvils, flywheel bearings and making the machine vibrate more than usual, which in turn can produce other issues on the chipper.

Inspecting Your Blades -

When inspecting your chipping blades, you want to be looking out for a flat or rounded edge on the blade. If there are any flat or rounded spots then it is time to replace them. People often ask if there is a time or amount of operating hours that the blades will last until before they require changing, the simple answer is no. It all depends on the timber you are chipping, foreign debris going through the chipper and the condition of your anvils.

Our Procedure -

The best way to remove the old blades is simple and safe. Always remove the spout from your machine before opening the chipping camber, leaving it on can cause extra wear to the hinge bolt and it ends up causing excessive wear. Our preferred way to remove the spout is to have it facing towards you, slacken the back handle then completely remove the front handle with the bottom plate, now lift the spout while tilting backwards to remove the spout from the machine.

Now you have got your chipping chamber open and can see your blades we can start the removal process. We want the blade we are working on to be pointing straight up, so you will need to turn the flywheel until it is. When turning the flywheel, you always want place your hand on the flywheel flat and push away from you. Placing your hand anywhere else on the flywheel is dangerous and risks getting caught when it spins on the engine compression.

You will need to use a pick or small screw driver to remove debris build up around the nuts and in the hex bolt heads. You want to make sure you get the hex head as clean as you can, otherwise if the allen key does not fit in all the way when applying pressure, it could end up slipping out and damaging the hex head.

Insert your Forst timber block, or a short block of timber in the back side of the cutting wheel against the lid. Using a 10mm allen key and a short 1/2” 24mm socket on a 1/2” 2ft breaker bar, you want to push away with the breaker bar while holding the allen key in place. Once they have been loosened, the nuts can be removed by hand. We usually take the bottom bolts out first and work our way up, bear in mind that the blade will come away when the last bolt is removed. *ADD NEW STYLE BOLT HERE *Newer style chipping flywheels might not have hex bolts, this means you have the square style bolt holes. Meaning there is a square hole in the cutting wheel and the square bolts slot through, this makes it easier when changing blades as you do not need to hold them with an allen key.

Once the blade is removed, dislodge your timber block, then spin the cutting wheel again with the flat of your hand away from you to get the other blade in straight up position and repeat the process.

With the old blades removed, we want to prep the chipping wheel ready to install our new blades. Using a flat headed screwdriver, you want to scrap all the debris that builds up behind the blade and in the bolt hole. Make sure you get all the debris out of the corner of blade stop on the cutting flywheel allowing the new blade to push up against it. Do this process for both blade seats on the cutting wheel.

Now it's time to install your new or sharpened blades. Our engineers and Forst will always recommend that whenever changing the blades, you install new bolts with new cerated washers. This is done because the bolts have been shown too stretch due to the torque and stress that is created while chipping. Carefully fit the new blades into place and fit the top bolt with cerated washer, just tighten this bolt up finger tight. Install the rest of the bolts by hand, remember that the bolt goes in blade side, then a cerated washer followed by the nut on the flywheel side. Once they are all in finger tight, place the timber block in the front of the cutting wheel closest to you. We now need to torque the bolts up correctly, the torque setting is 310nm for the Forst blade bolts and this is the same across all Forst chipper models.

We use a 1/2” torque bar as anything larger will struggle to access the nut on the 6” models, as the flywheel pocket is narrow. Using your 10mm allen key and torque bar set to 310nm with a short 24mm socket, you want to tighten nuts with the bar and hold the allen key steady. Tighten until the torque bar clicks, do the same for all bolts and then go over all bolts again to check none have loosened. With your sharp blade now fitted, be very careful when leaning over the cutting wheel as the blade edge sticks up slightly and you could catch yourself when working over it.

Remove the timber block and spin the cutting wheel until the other empty blade seat is facing upwards and repeat the process to install the other blade.

Now we are good to go ahead and close the chamber lid down, tighten lid bolts and then reinstall the spout, complete this in the reverse order to the process it was removed. It is recommended to check your Forst blades daily before you start any work with it and to change when excessively worn. It is good to keep three sets of blades in rotation, one on the machine, one sharp set on the shelf and the other set getting sharpened. I know it may sound over the top but as discussed at the beginning of this guide, chipping with blunt blades will end up causing more damage to various components on the machine.