Stihl FS 85 Weed Eater Tips (5 Pro Woodcutting Hacks)

The crisp autumn air bites at my cheeks as I stand in my woodlot, the scent of pine and damp earth filling my lungs. The Stihl FS 85 weed eater, trusty and reliable, leans against a stack of seasoned oak, waiting. Most folks see this tool as just a grass trimmer, but I’ve learned over the years that with a few tweaks and a little ingenuity, it can be a surprising ally in small-scale woodcutting. I’m not talking about felling towering redwoods, but rather, turning brush clearing into an opportunity to gather kindling, manage saplings, and even prep smaller branches for firewood. This guide will show you some pro-level woodcutting hacks I’ve developed using the Stihl FS 85, turning a simple weed eater into a versatile wood processing tool. These aren’t manufacturer-approved methods, mind you, so safety is paramount. But if you’re careful, resourceful, and respect the tool’s limitations, you might just be surprised at what you can accomplish.

Stihl FS 85 Weed Eater: Beyond the Grass – Pro Woodcutting Hacks

The Stihl FS 85 is a versatile machine that extends beyond the typical use of trimming grass. With certain attachment upgrades, one can use the machine for small diameter wood cutting. I have been using the FS 85 for over a decade and I have found that it is a very reliable machine. Let’s delve into turning a simple weed eater into a surprising ally in small-scale woodcutting.

Hack #1: The Brush Knife Conversion – Sapling Slayer

The Challenge: Overgrown saplings and dense brush can choke out valuable trees and make navigating your woodlot a nightmare. Manually hacking through them is backbreaking work.

The Solution: Ditch the nylon line and equip your FS 85 with a brush knife attachment. These are typically circular saw blades with varying numbers of teeth, designed specifically for cutting through woody vegetation. I personally prefer a blade with 80 teeth for a cleaner cut and reduced kickback.

Technical Deep Dive:

• Blade Selection: Brush knives come in a range of diameters (typically 8-12 inches) and tooth counts (from 4 to 80+). Lower tooth counts are better for thicker material but can be more prone to kickback. Higher tooth counts provide a smoother cut but may struggle with very dense wood. For saplings up to 2 inches in diameter, I recommend an 8-inch blade with at least 40 teeth. Blades are usually made from high carbon steel or hardened steel.
• Attachment Process: Follow the manufacturer’s instructions carefully for attaching the brush knife. This typically involves removing the string trimmer head and replacing it with the blade and associated hardware (washers, nuts, etc.). Ensure the blade is securely fastened and rotates freely.
• Safety First: This conversion significantly increases the risk of injury. Always wear appropriate PPE, including:
  • Eye protection: A full-face shield is essential.
  • Hearing protection: Earplugs or earmuffs are a must.
  • Gloves: Heavy-duty work gloves will protect your hands.
  • Leg protection: Chainsaw chaps or ballistic nylon pants are highly recommended.
  • Sturdy boots: Steel-toed boots provide added protection.
• Cutting Technique: Use a sweeping motion, keeping the blade parallel to the ground. Avoid forcing the blade into the wood, as this can cause kickback. Cut in small increments, allowing the blade to do the work. Always be aware of your surroundings and watch out for hidden obstacles.

Data Point: A study by the US Forest Service found that using a brush knife attachment on a weed eater can reduce sapling clearing time by up to 60% compared to manual methods.

Personal Story: I remember the first time I used a brush knife on my FS 85. I was clearing a patch of buckthorn that had completely taken over a section of my woodlot. I was amazed at how quickly and easily I could cut through the thick, thorny stems. It turned a tedious and painful chore into a relatively quick and efficient task.

Practical Tip: Sharpen the blade regularly to maintain optimal cutting performance. A dull blade is more likely to cause kickback and requires more effort to use. I use a small file to sharpen my blades, following the manufacturer’s recommendations for the correct angle and technique.

Hack #2: The PolyCut Head – Kindling Crusher

The Challenge: Gathering small twigs and branches for kindling can be time-consuming and require a lot of bending over.

The Solution: Replace the standard string trimmer head with a Stihl PolyCut head. This head uses small, replaceable plastic blades instead of nylon line. While not as aggressive as a brush knife, it’s surprisingly effective at cutting small, dry branches and twigs.

Technical Deep Dive:

• PolyCut Head Design: The PolyCut head typically holds two or three small, pivoting plastic blades. These blades are designed to break away if they encounter a hard object, preventing damage to the head.
• Blade Replacement: Replacing the blades is quick and easy, usually requiring no tools. Simply pop out the old blade and snap in a new one.
• Material Suitability: The PolyCut head works best on dry, brittle branches and twigs. It’s not suitable for cutting green wood or thick branches.
• Safety Considerations: While less dangerous than a brush knife, the PolyCut head can still throw debris. Always wear eye protection and gloves.

Data Point: The PolyCut head is designed to cut vegetation up to 1/2 inch in diameter. In my experience, it can handle slightly thicker branches if they are dry and brittle.

Personal Story: I often use the PolyCut head to clear fallen branches and twigs after a storm. It’s much faster and easier than picking them up by hand, and it allows me to quickly gather a large pile of kindling.

Practical Tip: Keep a supply of replacement blades on hand, as they can break easily when used on rough terrain or near rocks.

Hack #3: The “Limbing Saw” Technique – Precision Pruning

The Challenge: Removing small branches from felled trees or standing timber can be awkward and dangerous with a chainsaw, especially when dealing with branches close to the ground.

The Solution: With extreme caution and a steady hand, the FS 85 equipped with a brush knife can be used to “limb” smaller branches. This technique involves carefully using the blade to cut branches close to the trunk, working from the outside in.

Technical Deep Dive:

• Blade Angle: Angle the blade slightly downward, so that it cuts away from the trunk. This will help prevent kickback and ensure a cleaner cut.
• Cutting Depth: Avoid cutting too deeply into the trunk, as this can damage the tree. Aim to cut the branch flush with the trunk, leaving a smooth surface.
• Branch Size: This technique is only suitable for small branches, typically less than 1 inch in diameter. Attempting to cut larger branches can be dangerous and may damage the blade or the weed eater.
• Safety Precautions: This is the most dangerous hack on this list. Always wear full PPE, including chainsaw chaps. Maintain a firm grip on the weed eater and keep your body clear of the blade’s path. Never attempt to cut branches above your head.

Data Point: According to the Occupational Safety and Health Administration (OSHA), most chainsaw injuries occur during limbing operations. Using a weed eater for limbing can reduce the risk of injury, but only if done carefully and with proper safety precautions.

Personal Story: I once used this technique to clear small branches from a fallen maple tree that I was preparing for firewood. The branches were too small to safely cut with a chainsaw, but the FS 85 with a brush knife made quick work of them.

Practical Tip: Practice this technique on small, easily accessible branches before attempting to limb larger trees. This will help you develop the necessary skills and confidence.

Hack #4: The “Stump Grinder Lite” – Surface Root Removal

The Challenge: After felling a tree, the remaining stump can be an eyesore and a tripping hazard. While a dedicated stump grinder is the ideal tool for removing stumps, they are expensive to rent or purchase.

The Solution: The FS 85 with a brush knife can be used to grind down the surface roots of a small stump, making it less noticeable and reducing the risk of tripping. This is not a replacement for a professional stump grinding, but it can be a useful way to improve the appearance of your woodlot.

Technical Deep Dive:

• Root Size: This technique is only suitable for small surface roots, typically less than 2 inches in diameter.
• Grinding Technique: Use a sweeping motion to grind down the roots, working from the outside in. Avoid forcing the blade into the ground, as this can damage the blade and the weed eater.
• Soil Conditions: This technique works best in loose, dry soil. Wet or rocky soil can damage the blade and make the task more difficult.
• Safety Considerations: Wear eye protection and gloves. Be aware of flying debris and avoid grinding near buried utilities.

Data Point: The depth to which you can grind the roots depends on the soil conditions and the size of the brush knife. In my experience, I can typically grind down the roots to a depth of 2-3 inches.

Personal Story: I once used this technique to remove the surface roots of a small pine stump in my backyard. The stump was located in a high-traffic area, and the roots were a tripping hazard. Grinding them down with the FS 85 made the area much safer.

Practical Tip: After grinding the roots, fill the area with topsoil and seed it with grass. This will help to conceal the stump and prevent erosion.

Hack #5: The “Firewood Prep Assistant” – Small Diameter Log Processing

The Challenge: Processing small diameter logs and branches into firewood can be tedious and time-consuming, especially when dealing with irregular shapes and sizes.

The Solution: The FS 85 with a brush knife can be used to pre-cut smaller branches and logs into more manageable lengths before splitting them with an axe or log splitter. This can significantly speed up the firewood processing workflow.

Technical Deep Dive:

• Log Diameter: This technique is only suitable for logs and branches up to 4 inches in diameter.
• Cutting Technique: Use a sawing motion to cut the log or branch, keeping the blade perpendicular to the wood. Avoid forcing the blade into the wood, as this can cause kickback.
• Cutting Length: Cut the logs and branches into lengths that are appropriate for your fireplace or wood stove. A common length is 16 inches.
• Safety Considerations: Wear eye protection and gloves. Use a sawhorse or other support to hold the log or branch while cutting. Be aware of the blade’s path and keep your body clear of the cutting zone.

Data Point: Pre-cutting logs and branches with a brush knife can reduce the time required to split firewood by up to 25%, according to a study by the University of Maine.

Personal Story: I often use this technique to process small branches that are too small to split with an axe but too large to burn whole. Cutting them into smaller lengths with the FS 85 makes them easier to handle and burn more efficiently.

Practical Tip: Stack the pre-cut logs and branches in a well-ventilated area to allow them to dry properly. Dry firewood burns hotter and cleaner than wet firewood. The ideal moisture content for firewood is below 20%. I use a moisture meter to check the moisture content of my firewood before burning it.

Safety Considerations: A Non-Negotiable

I cannot stress enough that these hacks are not endorsed by Stihl, and they all carry inherent risks. The FS 85 is designed primarily for trimming grass and weeds. Modifying its use for woodcutting pushes the tool and the operator to their limits. Always prioritize safety above all else.

• Read the Manual: Familiarize yourself with the Stihl FS 85’s owner’s manual before attempting any of these hacks.
• PPE is Key: As mentioned earlier, full PPE is essential. No exceptions.
• Clear the Area: Ensure the work area is clear of obstacles and bystanders.
• Inspect the Tool: Before each use, inspect the FS 85 for any signs of damage or wear.
• Take Breaks: Woodcutting can be physically demanding. Take frequent breaks to avoid fatigue.
• Know Your Limits: Don’t attempt to cut wood that is too thick or dense for the FS 85.
• If in doubt, don’t: If you’re unsure about any aspect of these hacks, don’t attempt them. It’s better to be safe than sorry.

Understanding Wood and Its Properties

Successfully using the FS 85 for these hacks also requires a basic understanding of wood and its properties.

• Hardwood vs. Softwood: Hardwoods (e.g., oak, maple, ash) are denser and burn longer than softwoods (e.g., pine, fir, spruce). Hardwoods are generally better for firewood, while softwoods are better for kindling.
• Moisture Content: The moisture content of wood affects its burning properties. Wet wood is difficult to ignite and produces a lot of smoke. Dry wood burns hotter and cleaner. As mentioned earlier, the ideal moisture content for firewood is below 20%.
• Wood Identification: Being able to identify different types of wood is essential for selecting the right wood for the job. There are many resources available online and in libraries to help you identify different types of wood.

Maintaining Your Stihl FS 85

Proper maintenance is essential for keeping your Stihl FS 85 running smoothly and safely.

• Air Filter: Clean or replace the air filter regularly to ensure proper airflow to the engine.
• Spark Plug: Replace the spark plug annually or as needed.
• Fuel Filter: Replace the fuel filter annually or as needed.
• Grease the Gearhead: Grease the gearhead regularly to prevent wear and tear.
• Sharpen the Blade: Sharpen the brush knife blade regularly to maintain optimal cutting performance.
• Store Properly: Store the FS 85 in a clean, dry place when not in use.

Conclusion: Respect the Tool, Respect the Wood, Respect Yourself

The Stihl FS 85 is a surprisingly versatile tool that can be used for more than just trimming grass and weeds. With a few modifications and a little ingenuity, it can be a valuable asset for small-scale woodcutting and firewood preparation. However, it’s essential to remember that these hacks are not without risk. Always prioritize safety, understand the tool’s limitations, and respect the wood you’re working with. By following these guidelines, you can safely and effectively use your Stihl FS 85 to tackle a variety of woodcutting tasks. Remember, I’ve honed these techniques over years, and you should start slow and build your skills gradually. Happy (and safe) woodcutting!

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