Husqvarna FS 400 LV Blade Change: Complete Step-by-Step Guide to Removing, Installing, and Checking a Diamond Blade

A Husqvarna FS 400 LV blade change is a straightforward maintenance procedure when the correct safety steps, blade direction, flange setup, and tightening procedure are followed. The FS 400 LV is a professional petrol-powered push floor saw designed for cutting concrete and asphalt. The current U.S. version uses an 11.7-horsepower Honda engine, accepts blades up to 20 inches, and provides a maximum cutting depth of approximately 7.5 inches.

Changing the diamond blade may be necessary when switching between concrete and asphalt, changing blade diameter, replacing a worn blade, or installing a blade with a different bond or segment design.

The most important rule is to never treat blade replacement as simply removing one disc and installing another. The blade, flanges, arbor, rotation direction, blade guard, water system, and mounting hardware should all be inspected during the process.

When Should You Change the Blade on a Husqvarna FS 400 LV?

A diamond blade should be removed or replaced when it is no longer suitable for safe and efficient cutting.

Common reasons include:

• Segments are worn

• Segment loss

• Cracked steel core

• Warped blade

• Damaged arbor hole

• Excessive vibration

• Changing from concrete to asphalt

• Changing from asphalt to concrete

• Installing a different blade diameter

• Switching between different aggregate conditions

• Blade glazing that cannot be corrected

A blade should also be removed if unusual vibration or noise starts suddenly.

Do not continue cutting with a visibly damaged diamond blade.

Husqvarna FS 400 LV Maximum Blade Size

The current North American FS 400 LV accepts a maximum 20-inch diamond blade and is rated for approximately 7.5 inches of maximum cutting depth.

Other international configurations have been offered with 450 mm or 500 mm blade capacities, so the specific machine identification plate should always be checked before purchasing a replacement blade.

The correct blade must match:

• Approved diameter

• Arbor size

• Maximum RPM

• Material being cut

• Wet or dry application

• Saw horsepower

• Cutting depth

Never install a blade larger than the machine permits.

Safety Before Changing the FS 400 LV Blade

A diamond blade may remain extremely hot after cutting.

Husqvarna's blade-removal instructions state that the machine should be allowed to cool and protective gloves should be used when handling diamond blades after operation.

Before beginning:

1. Move the saw to a stable, level surface.

2. Stop the engine.

3. Put the engine ON/OFF switch in the OFF position.

4. Allow the blade and machine to cool.

5. Shut off the water supply.

6. Disconnect the water hose from the blade guard.

7. Wear gloves.

8. Wear safety glasses.

9. Keep the machine from rolling.

10. Remove dirt and slurry from the blade area.

Never attempt to change the blade while the engine is running.

Clean the Blade Area First

Concrete slurry can accumulate around:

• Blade guard

• Arbor

• Blade shaft

• Flanges

• Fasteners

• Water fittings

Cleaning this area before removing the blade makes inspection easier and helps prevent contamination from becoming trapped between the flange and blade.

A dirty flange can prevent the blade from sitting flat.

That may lead to:

• Blade wobble

• Uneven cutting

• Excessive vibration

• Premature bearing wear

• Irregular segment wear

Use appropriate cleaning methods without forcing water or debris into bearings or engine components.

Raise the Blade

Before removing the blade guard, raise the blade fully out of the cutting position.

The FS 400 LV includes a retractable handwheel and depth-control system that allows the operator to raise or lower the blade. Husqvarna also provides a clear cutting-depth indicator as part of the machine design.

Raising the blade provides better access and keeps it away from the ground during removal.

Disconnect the Water Hose

The FS 400 LV uses a quick connection between the water system and blade guard. Husqvarna specifically notes that the hose connection can be disconnected without tools.

Before removing the guard:

• Turn off water.

• Disconnect the hose.

• Move the hose away from the blade area.

This prevents the hose from being stretched or damaged when the guard is moved.

Remove or Raise the Blade Guard

Open or remove the blade guard according to the machine's configuration.

The guard protects the operator from:

• Blade contact

• Slurry

• Cutting debris

• Water spray

• Broken material

Inspect the guard while it is open.

Look for:

• Cracks

• Bent sections

• Loose mounting hardware

• Damaged water fittings

• Excessive wear

• Evidence of blade contact

A damaged blade guard should be repaired or replaced before operation.

Locate the Blade Screw and Flange

The diamond blade is held against the blade shaft by the outer flange and blade screw.

Before loosening the assembly, inspect:

• Outer flange

• Inner flange

• Blade screw

• Shaft

• Arbor

• Drive pin where applicable

Make note of how everything is assembled before removal.

Do not substitute random washers or hardware for original blade mounting components.

Loosen the Blade Screw

Use the proper wrench supplied with or specified for the FS 400 LV.

Support the blade while loosening the mounting screw so it cannot suddenly fall or shift.

Diamond floor-saw blades can be heavy, particularly at larger diameters.

Keep fingers clear of the blade edge and flange.

Do not strike the wrench with another tool unless the operator manual specifically permits it.

Remove the Outer Flange

Once the blade screw has been removed, carefully remove the outer flange.

Set it on a clean surface.

Immediately inspect it for:

• Concrete slurry

• Rust

• Burrs

• Distortion

• Cracking

• Uneven wear

The flange surface that contacts the blade should be flat and clean.

Even small pieces of dried concrete between the flange and blade may affect alignment.

Remove the Old Diamond Blade

Support the blade with both hands and slide it carefully from the blade shaft.

Do not allow it to fall against the machine or ground.

Once removed, inspect the blade.

Look for:

• Missing segments

• Cracks

• Warped steel core

• Damaged arbor

• Uneven wear

• Blue discoloration from heat

• Excessive undercutting

• Segment wear limit

If the blade is being removed only to change applications, store it vertically or in an appropriate blade rack so the core cannot become bent.

Inspect the Blade Shaft

The blade shaft should be checked every time a blade is removed.

Look for:

• Damage

• Excessive play

• Corrosion

• Dirt

• Worn threads

• Bent components

• Damaged drive features

The FS 400 LV parts structure includes a dedicated blade shaft and associated blade-guard components, making the shaft assembly a critical service area of the saw.

If you detect side-to-side movement in the shaft, do not simply install another blade.

Bearing or shaft service may be required.

Clean the Flanges

Clean both blade-contact surfaces thoroughly.

Flanges should be:

• Flat

• Clean

• Dry enough for inspection

• Free from concrete buildup

• Free from deep scoring

Do not grind a damaged flange flat by hand.

A severely worn or distorted flange should be replaced with the proper part.

Choose the Correct New Blade

The replacement blade should be matched to the material.

Concrete Blade

Choose according to:

• Cured concrete hardness

• Aggregate

• Reinforcement

• Saw horsepower

• Wet or dry use

Reinforced Concrete Blade

Use a blade rated for cutting concrete containing:

• Rebar

• Wire mesh

• Reinforcing steel

Asphalt Blade

Use an asphalt-specific blade for asphalt pavement.

Asphalt is highly abrasive and usually requires a different bond than cured concrete.

Using the wrong blade may result in rapid segment wear or poor cutting performance.

Check the Blade Rotation Direction

Before mounting the replacement blade, locate the rotation arrow on the blade.

The blade must be installed so its rotation arrow matches the direction of the saw's blade shaft.

Do not determine direction based only on which side of the blade has the printed label.

The rotation arrow is the correct reference.

Incorrect blade direction may result in:

• Poor cutting

• Glazing

• Reduced blade life

• Excessive heat

• Unusual wear

Install the New Blade

Carefully slide the new diamond blade onto the shaft.

Make sure:

• The arbor fits correctly.

• The blade sits flat.

• The rotation arrow is correct.

• Any drive pin aligns properly.

• The blade does not bind.

• The inner flange remains clean.

Do not force an incorrect arbor onto the shaft.

Never modify the blade arbor hole to make it fit.

Reinstall the Outer Flange

Place the clean outer flange against the blade.

The flange should sit fully against the steel core.

Inspect around the entire circumference to make sure nothing is trapped between the blade and flange.

Reinstall the blade screw.

Tighten the FS 400 LV Blade Screw

Husqvarna's published FS400LV instructions specify tightening the blade screw to a minimum of 40–45 Nm using the supplied wrench. The instructions describe using resistance between the cutting blade and ground to help hold the blade during tightening.

Do not guess at blade-fastener torque.

Improper tightening may result in:

• Blade movement

• Flange damage

• Shaft damage

• Difficulty removing the blade later

• Unsafe operation

Follow the operator manual for your exact production version.

Lower the Blade Guard

After the blade is secured, lower and properly close the blade guard.

The guard should:

• Move freely

• Clear the blade

• Be securely attached

• Have functioning water connections

• Remain aligned

Never operate the FS 400 LV with the blade guard raised or removed.

Reconnect the Water Hose

Reconnect the hose to the blade guard.

The FS 400 LV features an integrated water system, and Husqvarna highlights the quick-connect hose arrangement as part of the machine's design.

Before cutting, confirm that water reaches the cutting area adequately.

Poor water flow can cause:

• Overheating

• Excessive dust

• Faster blade wear

• Reduced cutting speed

Rotate the Blade Before Starting

With the engine still off, carefully check that the installed blade has adequate clearance and does not contact the guard.

Never place your hands in a hazardous position around the blade.

Confirm:

• Blade is centered

• Guard does not rub

• Flanges are seated

• Mounting screw is secure

Any binding should be investigated before starting the machine.

Start the Saw and Listen Carefully

After installation, Husqvarna instructs the operator to start the product and listen for unusual sounds. If abnormal sounds occur, the blade should be removed, inspected for damage, and installed again or replaced if damaged.

During the first startup:

• Keep bystanders away.

• Stand in the normal operator position.

• Do not immediately begin cutting.

• Listen for vibration or unusual noise.

• Watch the blade guard.

• Shut down immediately if something appears wrong.

Why Does the New Blade Wobble?

If a newly installed blade wobbles, stop the saw.

Possible causes include:

• Dirty flange

• Warped blade

• Bent blade shaft

• Worn bearings

• Damaged arbor

• Incorrect mounting

• Loose blade screw

Do not assume a new blade cannot be defective.

Remove it and inspect the complete mounting system.

Why Is the New Blade Cutting Slowly?

A freshly installed blade may cut slowly because:

• Wrong bond was selected

• Blade is installed backward

• Material is harder than expected

• Blade is glazing

• Engine is not reaching full speed

• Drive belt is slipping

• Cutting depth is excessive

• Water flow is inadequate

Avoid compensating by pushing the saw harder.

Excessive feed pressure can reduce blade RPM and increase heat.

Concrete Blade vs Asphalt Blade on the FS 400 LV

One of the most common reasons to perform a blade change is switching materials.

Concrete and asphalt require different blade characteristics.

Concrete can be hard and may require a comparatively softer bond.

Asphalt is softer but highly abrasive, so asphalt blades often use harder bonds and additional protection around the steel core.

A contractor cutting both materials should keep separate blades clearly marked.

How Often Should the Blade Be Changed?

There is no fixed hour interval.

Blade life depends on:

• Material

• Aggregate hardness

• Reinforcement

• Blade quality

• Bond type

• Water flow

• Cutting depth

• Operator technique

• Saw condition

The blade should be inspected before every job and replaced when damage or excessive wear is found.

Frequently Asked Questions About Husqvarna FS 400 LV Blade Changes

How do I change the blade on a Husqvarna FS 400 LV?

Stop the engine, allow the blade to cool, shut off and disconnect the water supply, open the guard, remove the blade screw and outer flange, remove the old blade, clean the mounting surfaces, install the new blade in the correct rotation direction, reinstall the flange and screw, torque correctly, close the guard, and reconnect the water.

What size blade does the FS 400 LV use?

The current North American FS 400 LV accepts a maximum 20-inch blade.

How deep can the FS 400 LV cut?

The current U.S. model is listed at a maximum cutting depth of approximately 7.5 inches.

What torque should the blade screw have?

Husqvarna's FS400LV instructions specify a minimum blade-screw tightening torque of approximately 40–45 Nm.

Which direction does the blade go?

Match the rotation arrow on the diamond blade to the direction of blade-shaft rotation.

Does the writing on the blade need to face outward?

Not necessarily. Use the rotation arrow and mounting requirements rather than the printed label as the primary guide.

Should I disconnect the water before removing the guard?

Yes. Husqvarna's removal procedure instructs operators to stop the water supply and disconnect the hose from the blade guard.

Should I let the blade cool first?

Yes. Husqvarna warns that diamond blades can become very hot after use and recommends allowing the machine to cool and using protective gloves.

Can I install an asphalt blade on the FS 400 LV?

Yes, provided it matches the machine specifications and is designed for asphalt.

Can I use a reinforced-concrete blade?

Yes. Use a blade specifically rated for reinforced concrete when cutting material containing rebar or mesh.

Why is my blade vibrating after replacement?

Inspect the flanges, blade shaft, arbor, blade core, bearings, and mounting hardware.

Can I run the saw without the blade guard?

No. The guard is an essential safety component and must be properly installed before operation.

Should the flange be cleaned every time?

Yes. Cleaning the flange during every blade change helps ensure the blade seats flat and runs correctly.

Can I put a larger than 20-inch blade on the FS 400 LV?

Not on the current U.S. model. Do not exceed the manufacturer's maximum approved blade diameter.

Do I need water when changing the blade?

No. The water supply should be turned off and the hose disconnected during the blade-change procedure. Reconnect it before wet cutting.

What should I do after installing the new blade?

Close the guard, reconnect water, start the saw, and listen carefully for abnormal noises before beginning the cut. Husqvarna specifically recommends stopping and inspecting the blade if unusual sounds occur.

Why does my blade screw keep loosening?

Possible causes include incorrect installation, damaged flanges, improper tightening, incorrect hardware, excessive vibration, or shaft problems. Stop using the saw until the cause is identified.

What should I inspect during every FS 400 LV blade change?

Inspect the blade, inner and outer flanges, arbor, blade shaft, mounting screw, blade guard, water connection, and surrounding hardware.

What is the most important part of changing an FS 400 LV blade?

Make sure the saw is completely shut down, the blade is correctly matched and oriented, the mounting surfaces are clean, the blade screw is tightened according to Husqvarna's specification, and the blade guard is fully installed before restarting the machine.