Replacing Viking GB455 Mulcher Blades


This is an informational blog on how I personally sharpened my Viking GB455 mulcher blades, do this at your own risk. These are not instructions.

Always remove the spark plug lead from the spark plug prior to doing any work on garden equipment.

Do not put your fingers in rotating parts of the machine. There is enough mass in the chipper drum to take a finger off.

Viking GB455

Flail Mulcher Chipper with side chute

Below you can see the blade for larger sticks and branches.

GB455 chipper blade chute

Tools Needed

(with amazon links)

Socket Set
Spanner Set10mm
Allen Key Set
Whetstone 180 Grit


Firstly I unplugged the spark plug and then took off the hopper off, I did this buy removing four bolts at the base.
GB455 shroud off

I then had to dig out some of the chips from the allen key bolt heads.

GB455 bolts cleaning

I was then able to get the 10mm socket onto the inside of the bolt, holding it in place with the Allen key while being very careful not to put my fingers or hands anywhere that the chipper barrel would spin and cause injury.

GB455 bolts

The bolt closest to the motor is a pain to get out, just had to go slowly and patiently.

GB455 bolt

When I got the bolts out of the blade, it fell down into the bottom of the drum so i unbolted the guards from the front and the bottom, this allowed the blade to fall down.

GB455 shroud guard

Blade out, time to get some measurements, clean it up and sharpen.

Viking GB455 blade

The blade measured 110mm x 35mm.
The holes measuring:
  • 20mm
  • 55mm - centre
  • 90mm
GB455 blade length

GB455 blade width

Clean up with a wire brush reveals the damage to the blade. We can see in the middle, there is a dip in the blade.

GB455 dull blade

Using the 180 grit whetstone / diamond board, i was able to clean up the worst of this edge.

This took around an hour and one sore arm.

GB455 blade

While I had it open, I took the measurements of the flail hammers

GB455 Hammer Length

GB455 hammer width

Something I had noticed after purchasing the unit second hand was a burn mark on the side of the tins opposite the motor, I had assumed that a bearing had gotten hot, however after investigating i found that there was no bearing on that side, and the unit had been used to spread straw at some point.

The straw had gotten bound up and resulted in a burn mark.

GB455 hot spot

GB455 bind up

Assembly of the unit is just the reverse of taking it apart.  Do not use any lubricants on the fixings as we do not want those coming apart.

Back to making mulch!

GB455 Mulch

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