4.1.4 – Remove and Replace Flail-Blades

Refer below to which Model blade and type of Pivot-Bolts applies to you.

This Pivot-Bolt applies to;

Model-20, Model-21 & Model-22 Blades

Is a three piece assembly; made up of a Pivot-Bush, a bolt which has both a left and right hand thread and a lock nut. The lock nut works, by the high friction created when it is wedged into a long taper.

To replace the flail-Blades, Follow these instructions to undo the Pivot-Bolt.

1 – Clean off any plant sap build up on the top and bottom surfaces, around the hex head surfaces and around the Anti-Fouling Blades with the chisel point of the fixed ring spanner. So that the Fixed Spanner can connect with the very shallow sides of the hex head on the pivot-bush.

2 – Fit the fixed ring spanner as shown below, so that it locks into the Anti-Fouling Blade, which prevents it from turning. Once fitted, it should stay there.

3 – To remove the lock nut, fit the small end of the double ended ring spanner to the lock-nut as shown below, with arrow facing upwards.

PLEASE NOT; THE LOCKNUT IS A NORMAL RIGH HAND THREAD AND YOU UNDO IT IN THE DIRECTION OF ANY NORMAL NUT.

In most cases you will be able to loosen the locknut & bolt, but hitting the end of the spanner with the palm of your hand, but if it has not been undone for some time and some rust has formed on the thread. Use a 300 to 400mm length of soft wood, or branch if out in the bush and tap in the direction shown on the spanner to loosen the tapered friction locking action.

Use fast but light taps, is best to break the friction grip. The Pivot-Bush is harder than the spanner and this prevents damaging the spanner.

4 – Once the friction grip is broken, remove the spanner and undo the locknut with your fingers. You are less likely to drop the lock-nut this way and put it somewhere safe as it is very easy to lose.

5 – Now fit the big end of the Ring-Spanner to the bolt head with the arrow facing upwards and use the same piece of wood to loosen the bolt.

PLEASE NOT; THE BOLT HAS AN UNUSUAL LEFT HAND THREAD AND YOU UNDO IT AS IF YOU WERE DOING UP ANY NORMAL BOLT.

I have had a number of customers who end up trying to undo the bolt as any normal bolt with ever increasing force, all this does is tighten up the bolt even more and makes it even more difficult to undo when they read this and realise that it is a left hand bolt.

Below is a pivot bolt assembly that was broken when excessive force was applied in the wrong direction, as can be seen by the indents from the ring spanner. This person was trying to undo the bolt as if it were a normal right hand threaded bolt. In this case applying enough force to break the head of the bolt off and crack the pivot bush.

6 – Once the tapered friction grip is broken, you should be able to undo the bolt by hand.

You are less likely to drop the lock-nut this way and put it somewhere safe with the other parts, as it is very easy to lose.

7 – Use the end of the spanner, to lever out the fixed ring spanner. you will find that the Pivot-Bush come out with it.

8 – Replace the worn Flail-Blade and reverse the procedure to reassemble.

PLEASE NOTE; You only have to do up the bolt and lock nut by hard hand pressure only. The length of the spanner give the approximate amount leverage to get the right torsion on the bolt and lock-nut when doing up.

This Pivot-Bolt applies to;

Model-15, Model-16, Model-17 & Model-19 Blades

On this page you will find articles and videos on how to quickly remover and replace BrushDestructor Flail-Blades, while the BrushDestructor Blade is both on and off your brush cutter. I will also show why it is important to check and ensure that pivot bolt lock nuts are torqued up very tight.

Tools required two 5/8 sockets or wrench, vice-grips and a removable thread locker.

A small amount of removable thread locking compound must be used on the bolt and nut when re-assembling the fasteners as this new nut is not a lock nut.

Below are the tools required to change the flail-blades on a BrushDestructor blade.

The first two, shown at the top of the picture below, are the socket and lock pin, to remove and replace metal blades that should have come with your brush cutter.

To remove and replace the Pivot Bolt assembly, you will need a 1 x 5/8 socket and 1 x 5/8 ring spanner, or a second 5/8 socket spanner shown at the bottom.

This video shows you how to replace all the Flail-Blades on a Model-17 blade and includes inspection of the impact rubber stop for damage. This same process can be used going back to the Model-15 blade.

This video shows you how I used to replace the Flail-Blades one at a time on a model-15 blade. It involves the removal of the bolt and bush as well, to inspect these, but history has proven that these pivot bolt assemblies last a very long time. I recommend watching this video, but unless you need to replace the bushes, I would use the Model-17 process to replace the Flail-Blades.

This Pivot-Bolt applies to;

Model-11 & Model-14 Blades

This video which is for the now obsolete non threaded bush washer, shows how to remove and insert Flail-Blades using a vice to hold an Allen key so that it is easy to undo and torque up the pivot bolt lock nut.

Tools Required to remove and replace Flail-Blades

Minimum tools required

Shifter, some sort of pliers and a 6mm Allen Key.

Best tools for the job

13mm (1/2″) socket in ratchet handle, vice grips and a 6mm Allen socket drive in handle.

Changing Flail-Blades on brush cutter

Use 6mm Allen key/drive to retain socket head bolt.
Use shifter or socket drive to remove lock nut.
Use pliers or vice grips to squeeze threaded bush washer between top and bottom plates.
Use 6mm Allen key/drive to unscrew socket head bolt out of threaded bush washer.
Release pliers or vice grips and slide out flail-blade and bush washer.

Reverse procedure to re-assemble.

If you have been using the blade hard for a long period of time, the threads of the bolt can get crushed against the Top Hub pivot hole making it had to undo the socket head bolt out of the bush washer. If this is the case you will need to remove the BrushDestructor blade from the brush cutter squeeze in a vice as shown.

This will give the extra pressure to prevent the bush washer from rotating and all you to apply the extra force required to unscrew the socket hard bolt with the damaged thread.