How to Put STIHL Plastic Blades on a Strimmer

To fit STIHL plastic blades, first identify the PolyCut mowing-head model, then push each matching blade into its own clean retaining slot until it locks securely in place. STIHL replacement blades are listed as suitable for the PolyCut 2-2 mowing head.

“Strimmer” is the common UK term; in the US, this tool is usually called a string trimmer or weed eater. The process is usually quick, but choosing the correct replacement blade matters more than forcefully trying to make a similar-looking one fit.

How STIHL PolyCut Plastic Blades Work

A PolyCut head uses removable plastic cutting blades instead of, or sometimes as an alternative to, nylon trimmer line. The blades swing from the head as it spins and are intended for cutting grass and light weeds.

They are useful when ordinary line wears too quickly in thicker grass, but they are still consumable parts. Replace a blade if it is cracked, heavily worn, bent, loose in its holder, or missing.

Plastic PolyCut blades are specific to the mowing head, not interchangeable across every STIHL strimmer.

The marking molded into the current head is the best starting point. Match replacement parts to the PolyCut designation, such as PolyCut 2-2 or PolyCut 20-3.

Choose the Right Blades Before Installing Them

Use this quick check before opening a blade pack or removing the trimmer head.

What You Find on the Trimmer	What to Buy	What It Means
PolyCut 2-2 molded on the head	STIHL replacement blades made for the PolyCut 2-2	STIHL part 4008 007 1000 is a pack of 8 replacement blades for the PolyCut 2-2 mowing head.
PolyCut 20-3	A complete replacement head listed for PolyCut 20-3	This is a different head design from the PolyCut 2-2.
No readable head marking	Identify the trimmer model and compare its parts listing with the old head	Do not buy a blade based only on its color, length, or a product photo.
Head is cracked, warped, or will not retain a blade	Replace the complete mowing head	A new blade cannot safely fix damaged blade retainers.

A PolyCut 2-2 blade pack is not a general-purpose STIHL plastic-blade pack.

How to Install Plastic Blades on a STIHL PolyCut Head

Plastic blades fit securely in a STIHL PolyCut head when they are correctly directed, fully retained, and installed as a balanced set.

Step 1: Shut Down and Secure the Strimmer

1. Turn off the engine or motor.
2. Remove the battery from a battery-powered trimmer. For a gas model, stop the engine and allow the cutting head to come fully to rest.
3. Set the tool on a stable, level surface with the cutting head facing upward.
4. Keep the throttle trigger clear and prevent anyone from starting the tool while you work.
5. Put on work gloves and safety glasses or a face shield before handling the cutting head. STIHL recommends work gloves and eye or face protection when working on cutting equipment.

Do not work on a head that is still spinning, connected to a battery, or sitting where it can roll and start unexpectedly.

Step 2: Remove the Old Plastic Blade

1. Find the worn, broken, or missing blade position in the PolyCut head.
2. Brush away packed grass, soil, and string from the blade slot and retainer.
3. Grip the old blade close to its mounting end rather than its cutting end.
4. Pull or slide the blade out in the reverse direction from which it was installed.

If the blade does not come out easily, stop rather than prying aggressively on the head. Packed debris may be blocking the retainer, or the head may be damaged. A blade holder that is split, rounded off, or unable to grip the blade cannot retain a blade securely.

Step 3: Match the New Blade’s Direction

Place the new blade beside one that is still correctly installed, if there is one. The new blade should point the same way and sit at the same angle as the other blades.

If all blades are removed, use the molded guides in the head to position the narrow mounting end in the blade channel. The broad cutting portion should extend outward from the head without twisting.

Do not trim or reshape a plastic blade to make it fit. A blade that does not enter the slot smoothly is usually the wrong type for that head or is being inserted in the wrong direction.

Step 4: Push the Blade Into the Retainer

1. Line up the blade’s mounting end with an empty blade guide or slot.
2. Slide or push it straight into the head’s retainer.
3. Continue until the blade reaches its stop and sits fully captured by the retaining lip or locking feature.
4. Pull the blade outward gently by hand to confirm that it cannot come free.

The blade should pivot or swing as its design allows, but its mounting end must remain held inside the head. If it pulls out, falls out, or sits crookedly, remove it and inspect the slot for dirt or damage before trying again.

Step 5: Fit a Balanced Set of Blades

Install matching blades in every blade position intended for plastic blades. Do not operate a PolyCut head with one blade missing or with mismatched blades on opposite sides.

A balanced head reduces vibration and helps the strimmer run smoothly. Replace any blade that is noticeably shorter, damaged, or distorted instead of pairing a new blade with a badly worn one.

Before restarting, rotate the head by hand with the machine switched off. Each blade should clear the guard and move freely without catching on grass, line, or the gearbox.

When to Replace the Complete PolyCut Head

Replace the whole head when the blade slots are damaged, the head is cracked, the retaining sections no longer hold blades, or the head has excessive wobble.

Removing the Old Head

The head must usually be locked to the gearbox before it can be removed. Use the locking method and fastening arrangement specified for that trimmer model.

1. Disconnect the battery or stop the engine.
2. Turn the head until the gearbox locking hole aligns.
3. Insert the correct locking pin or tool supplied for the trimmer.
4. Hold the gearbox locked while loosening the head according to the parts arrangement for that trimmer.
5. Remove the head, any washers, and hardware in the order they came off.

Do not assume every STIHL head uses the same thread direction or washer stack.

Selecting a PolyCut 20-3 Replacement Head

A PolyCut 20-3 is a different head from a PolyCut 2-2, so confirm the existing mowing-head marking and the strimmer’s parts listing before ordering.

For straight-shaft STIHL units, Forester sells a replacement described as replacing the STIHL PolyCut 20-3 and replacement part number 4002-710-2189. That particular replacement is a 3-plastic-blade head and includes 3 extra blades; those details apply to Forester’s own replacement product, not to every PolyCut head or blade kit.

Install a complete replacement head with the original washers and fasteners in their proper order. Lock the gearbox, tighten the head as specified for the trimmer, remove the locking tool, then turn the head by hand to make sure it spins freely without rubbing the guard.

Check the Blades Before You Start Trimming

Before each use, inspect the head with the power source disconnected.

Use this short checklist:

• Every plastic blade is fully seated in its retainer.
• Matching blade positions have matching blades installed.
• The head turns freely by hand.
• The debris guard is fitted and secure.
• Grass, string, wire, and soil are cleared from the head.
• No one is standing nearby when you start the trimmer.

Start the strimmer at low speed in a clear area and listen for unusual vibration. Stop immediately if the head shakes, a blade contacts the guard, or a blade appears to wobble more than the others.

Avoid striking pavement, fencing, rocks, tree trunks, or metal edging. Plastic blades can wear rapidly or break when they hit hard surfaces.

Common PolyCut Blade Problems

The Blade Will Not Go Into the Slot

First, check that the head is clean. Grass packed into the mounting channel can prevent the blade from reaching its retaining point.

If the slot is clear, compare the blade shape and mounting end with the original blade. A PolyCut 2-2 blade is head-specific, so a blade that looks close may still be the wrong part.

The Blade Goes In but Pulls Back Out

A correctly fitted blade should remain captured by the head while still being able to move as designed. If it pulls out easily, the blade may not be fully seated, the retainer may be clogged, or the plastic retaining section may be worn or broken.

Do not use tape, glue, wire, screws, or improvised clips to hold a blade in place. Replace the damaged head instead.

The Strimmer Vibrates After Fitting New Blades

Stop the tool and inspect the head. Vibration often means one blade is missing, seated differently from the others, damaged, or made for a different head.

Remove and refit the blade set so every position is correctly equipped. If vibration continues with matching blades installed, inspect the head and mounting hardware for damage.

Frequently Asked Questions

How do you attach a plastic blade to a STIHL strimmer?

Attach it by inserting the blade’s mounting end into the matching PolyCut head slot and pushing it fully into the retainer. The blade must sit securely enough that a gentle hand pull will not remove it, while still being able to swing normally from the head.

What are the plastic blades for on a strimmer?

Plastic blades cut grass and light weeds where nylon line may wear quickly. They are not metal brush-cutting blades, and they should not be used as a substitute for a metal cutting attachment in heavy brush or woody growth.

How do you remove a STIHL PolyCut head?

Disconnect the power source, lock the gearbox through its alignment hole with the correct pin or tool, then remove the head using the fastening arrangement for that trimmer model. The thread direction and washer order can vary, so match the old head’s model marking and parts listing before fitting another head.

What parts are available for STIHL strimmer heads?

Depending on the head, replaceable parts may include plastic blades, nylon line, spool components, caps, line inserts, washers, fasteners, and complete mowing heads. STIHL part 4008 007 1000 is a pack of 8 replacement blades for the PolyCut 2-2 head.

Are STIHL PolyCut blades good?

STIHL PolyCut blades are useful for routine grass and light-weed cutting when fitted to the correct compatible head. Their main advantages are quick replacement and a more rigid cutting edge than line, but they wear faster against hard obstacles and must be replaced when damaged.

Can I use a PolyCut 20-3 head on any STIHL trimmer?

No. A PolyCut 20-3 replacement head must match the trimmer’s shaft, gearbox fitting, guard, and approved cutting attachments. Forester’s PolyCut 20-3 replacement is listed for STIHL straight-shaft units, so confirm the exact trimmer model and existing head designation before buying.