520-120 Chainsaw Angles For Stihl (Expert Sharpening Tips)

I still remember the first time I tried sharpening a chainsaw. It was my grandfather’s old Stihl, a beast of a machine that had felled countless trees. I thought I knew what I was doing, but the results were… less than impressive. The chain cut crooked, vibrated like crazy, and dulled almost instantly. That’s when I learned that chainsaw sharpening, especially getting those angles right, is a real skill, and it’s crucial for both performance and safety. The “520-120” angles for Stihl chainsaws are a common topic, and understanding them can make all the difference. This guide will cover everything you need to know about achieving the perfect edge on your Stihl chain.

Understanding Chainsaw Sharpening Angles: The 520-120 for Stihl

The numbers “520-120” refer to the three primary angles you need to consider when sharpening a Stihl chainsaw chain:

Top Plate Cutting Angle (5°): This angle determines how aggressively the cutter bites into the wood.
Side Plate Angle (20°): This angle affects the smoothness and efficiency of the cut.
Depth Gauge Setting (0.025″ – 0.030″ or approximately 120° relative to the cutter): This controls how much wood each cutter takes.

These angles are crucial for optimal performance and safety. Let’s break down each angle in detail.

Top Plate Cutting Angle (5°)

The top plate cutting angle, typically around 5° for Stihl chains, is the angle of the top edge of the cutter relative to the bar.

Function: This angle dictates how aggressively the cutter bites into the wood. A more acute angle (smaller number) results in a more aggressive cut but dulls faster. A more obtuse angle (larger number) cuts more slowly but stays sharp longer.
Stihl Recommendation: Stihl generally recommends a 5° top plate cutting angle for most of their chains, providing a good balance between cutting speed and edge durability.
Why it Matters: If this angle is too steep, the chain will grab and be prone to kickback. If it’s too shallow, the chain will skate over the wood and not cut effectively.
Practical Tip: When using a chainsaw sharpening jig, ensure it is set to the correct top plate angle. I like to double-check the setting with a protractor.

Side Plate Angle (20°)

The side plate angle, usually around 20° for Stihl chains, is the angle of the side of the cutter relative to the bar.

Function: This angle affects the smoothness and efficiency of the cut.
Stihl Recommendation: Stihl recommends a 20° side plate angle for most of their chains. This angle provides a good balance between cutting speed and smoothness.
Why it Matters: If this angle is incorrect, the chain can vibrate excessively, cut unevenly, or even damage the wood.
Practical Tip: Maintain a consistent side plate angle throughout the sharpening process. Using a file guide with clear angle markings is extremely helpful.

Depth Gauge Setting (0.025″ – 0.030″ or approximately 120° relative to the cutter)

The depth gauge setting is the height difference between the top of the cutter and the depth gauge (also known as the raker). This setting determines how much wood each cutter takes per pass.

Function: Controls the “bite” of the chain. Too high, and the chain won’t cut; too low, and it will grab and kickback.
Stihl Recommendation: Stihl typically recommends a depth gauge setting of 0.025″ – 0.030″ for most of their chains. Some users prefer to describe this setting using a relative angle of approximately 120° to the cutter.
Why it Matters: An incorrectly set depth gauge is a primary cause of chainsaw kickback. It also affects the efficiency and smoothness of the cut.
Practical Tip: Use a depth gauge tool to ensure consistent and accurate settings. I prefer flat files for lowering the depth gauges, as they provide a smooth, even surface.

Takeaway: Understanding these three angles is the foundation of effective chainsaw sharpening. Getting them right means a safer, more efficient, and more enjoyable cutting experience.

Tools and Equipment for Chainsaw Sharpening

Having the right tools makes chainsaw sharpening significantly easier and more accurate. Here’s a list of essential equipment:

Chainsaw Vise: A vise securely holds the chainsaw bar in place, allowing for precise and safe sharpening. I prefer a bar-mounted vise that attaches directly to the bar.
Round Files: These are used to sharpen the cutters. The correct file size depends on the chain pitch (the distance between the chain’s rivets).
Flat File: Used for lowering the depth gauges (rakers).
File Guide: A file guide helps maintain consistent angles during sharpening.
Depth Gauge Tool: This tool ensures accurate depth gauge settings.
Gloves: Protect your hands from sharp edges and splinters.
Eye Protection: Safety glasses are a must to protect your eyes from metal filings.
Ruler or Caliper: For measuring depth gauge settings.
Magnifying Glass (Optional): Helps to inspect the cutters for damage.

File Size Chart for Stihl Chains:

Chain Pitch (inches)	File Size (inches)	File Size (mm)
0.325″	5/32″	4.0 mm
3/8″	13/64″	5.0 mm
0.404″	7/32″	5.5 mm

Why These Tools Matter:

Precision: The right tools allow for accurate angle and depth control.
Safety: Securely holding the chainsaw and protecting yourself are paramount.
Efficiency: Having the right tools speeds up the sharpening process and reduces the risk of errors.

My Personal Preference: I’ve found that investing in high-quality files and a reliable file guide is well worth the cost. They make a noticeable difference in the sharpness and longevity of the chain. I also recommend keeping your tools clean and well-maintained.

Takeaway: Investing in quality sharpening tools will save you time, money, and frustration in the long run. Make sure you have the right tools for your chain pitch.

Step-by-Step Guide to Sharpening Your Stihl Chainsaw

Now, let’s dive into the practical steps of sharpening your Stihl chainsaw. I’ll walk you through each stage, from securing the chainsaw to fine-tuning the depth gauges.

Step 1: Securing the Chainsaw

Place the chainsaw on a stable surface: I usually use a workbench or a sturdy stump.
Engage the chain brake: This prevents the chain from moving during sharpening.
Secure the chainsaw bar in a vise: Ensure the vise is tight enough to hold the bar firmly but not so tight that it damages the bar.

Step 2: Identifying the Cutters

Locate the cutters: These are the sharp teeth on the chain.
Identify the shortest cutter: This will be your reference point. All other cutters need to be filed down to match this length.
Mark the starting cutter: Use a marker to indicate where you began. This helps you keep track of your progress.

Step 3: Sharpening the Cutters

Insert the round file into the file guide: Make sure the file is the correct size for your chain pitch.
Position the file guide on the cutter: Align the file guide according to the 5° top plate cutting angle and the 20° side plate angle. Most file guides have markings to help you achieve these angles.
File the cutter: Use smooth, even strokes, filing from the inside of the cutter outwards. Maintain a consistent angle and pressure. I usually aim for 3-5 strokes per cutter.
Repeat for all cutters on one side: Work your way around the chain, sharpening each cutter to the same length and angle.
Flip the chainsaw bar in the vise: Sharpen the cutters on the opposite side of the chain.

Step 4: Lowering the Depth Gauges (Rakers)

Use a depth gauge tool: Place the tool over the depth gauge.
File the depth gauge: Use a flat file to lower the depth gauge until it is flush with the top of the depth gauge tool.
Round off the front of the depth gauge: This helps prevent the depth gauge from catching on the wood. I use the flat file to gently round off the front edge.
Repeat for all depth gauges: Ensure all depth gauges are set to the same height.

Step 5: Inspecting and Testing

Inspect the cutters: Check for any damage or irregularities.
Test the chain: After sharpening, test the chain on a piece of wood. The chain should cut smoothly and aggressively without excessive vibration.

Common Mistakes to Avoid:

Using the wrong file size: This can damage the cutters and reduce the chain’s lifespan.
Filing at the wrong angle: This results in a dull or uneven cut.
Over-filing: Removing too much material weakens the cutters.
Neglecting the depth gauges: Improperly set depth gauges can cause kickback and reduce cutting efficiency.

My Personal Tip: I always take my time when sharpening. Rushing the process can lead to mistakes and compromise safety. Patience and attention to detail are key.

Takeaway: Sharpening your chainsaw is a skill that improves with practice. Follow these steps carefully, and don’t be afraid to experiment to find what works best for you.

Understanding Stihl Chainsaw Chain Types and Their Sharpening Needs

Stihl offers a variety of chainsaw chains, each designed for specific applications. Understanding the different chain types and their unique sharpening needs is essential for optimal performance and longevity.

Common Stihl Chain Types

Rapid Micro (RM): A low-vibration chain with a semi-chisel cutter. It’s a good all-around chain for general use.
- Sharpening Needs: The RM chain is relatively easy to sharpen and maintain. The 5°, 20°, and 0.025″ – 0.030″ depth gauge settings apply.
Rapid Super (RS): A high-performance chain with a full-chisel cutter. It’s designed for fast cutting in clean wood.
- Sharpening Needs: The RS chain requires more precise sharpening due to its aggressive cutting profile. Maintaining the correct angles is crucial.
Rapid Duro (RD): A carbide-tipped chain designed for cutting abrasive materials like dirty wood or roots.
- Sharpening Needs: The RD chain requires specialized sharpening tools and techniques. Standard files will not work. Use a diamond grinding wheel or a carbide sharpener.
PMMC3 (Picco Micro Mini Comfort 3): A narrow kerf chain designed for smaller chainsaws.
- Sharpening Needs: The PMMC3 chain requires smaller files and more delicate sharpening techniques.

Chain Pitch and Its Impact on Sharpening

The chain pitch is the distance between any three consecutive rivets divided by two. Common chain pitches include 0.325″, 3/8″, and 0.404″.

Impact on Sharpening: The chain pitch determines the size of the file needed for sharpening. Using the wrong file size can damage the cutters. Refer to the file size chart in the “Tools and Equipment” section.

Identifying Your Chain Type

Check the Stihl part number: The part number is usually stamped on the drive links of the chain. You can use this number to identify the chain type and find specific sharpening recommendations.
Consult the Stihl website or your local dealer: They can help you identify your chain type and provide sharpening advice.

My Personal Experience: I once tried sharpening a Rapid Duro chain with a standard file. It was a complete waste of time and effort. I quickly learned the importance of using the right tools for the job.

Takeaway: Knowing your chain type and its specific sharpening needs is crucial for achieving optimal performance and extending the chain’s lifespan.

Advanced Sharpening Techniques and Troubleshooting

Once you’ve mastered the basics of chainsaw sharpening, you can explore more advanced techniques to fine-tune your skills and address common issues.

Using a Chainsaw Sharpener

A chainsaw sharpener is a power tool that automates the sharpening process. It can save time and effort, especially if you have a lot of chains to sharpen.

Types of Sharpeners: Bench-mounted sharpeners are more accurate and versatile than handheld sharpeners.
Setting the Angles: Most sharpeners allow you to adjust the top plate cutting angle, side plate angle, and depth gauge setting.
Using the Sharpener: Follow the manufacturer’s instructions carefully. Ensure the chain is properly aligned and the angles are correctly set.

Troubleshooting Common Sharpening Issues

Chain cuts crooked: This is often caused by uneven sharpening. Ensure all cutters are the same length and angle.
Chain vibrates excessively: This can be due to incorrectly set side plate angles or damaged cutters.
Chain dulls quickly: This may be caused by over-filing, using the wrong file size, or cutting abrasive materials.
Chain kicks back: This is usually due to improperly set depth gauges.

Advanced Techniques

Grinding: Grinding is a more aggressive sharpening technique that can be used to reshape damaged cutters. It requires specialized equipment and skills.
Profiling: Profiling involves adjusting the shape of the cutter to optimize its cutting performance. This is an advanced technique best left to experienced sharpeners.

Case Study: I once had a chainsaw chain that was cutting crooked despite my best efforts. After carefully inspecting the chain, I discovered that one of the cutters was bent. I used a grinding wheel to reshape the cutter, and the chain cut straight again.

My Advice: Don’t be afraid to experiment and try new techniques, but always prioritize safety. If you’re unsure about something, consult a professional.

Takeaway: Advanced sharpening techniques can help you fine-tune your skills and address complex issues. However, it’s important to have a solid understanding of the basics before attempting these techniques.

Maintaining Your Chainsaw Chain for Optimal Performance

Sharpening is only one aspect of chainsaw chain maintenance. Proper care and maintenance can significantly extend the life of your chain and improve its performance.

Regular Cleaning

Remove debris: After each use, remove sawdust, pitch, and other debris from the chain.
Use a brush or compressed air: A stiff brush or compressed air can help dislodge stubborn debris.
Clean the bar groove: The bar groove can accumulate debris, which can affect chain lubrication. Use a bar groove cleaner or a screwdriver to remove the debris.

Lubrication

Use high-quality bar and chain oil: This oil is specially formulated to lubricate the chain and bar.
Check the oil level regularly: Ensure the oil reservoir is always full.
Adjust the oiler: Adjust the oiler to provide adequate lubrication. The chain should be slightly wet with oil during operation.

Tensioning

Check the chain tension regularly: The chain should be snug on the bar but still able to be pulled around by hand.
Adjust the tension: Use the chain tensioning screw to adjust the tension.
Avoid over-tensioning: Over-tensioning can damage the chain and bar.

Storage

Clean and lubricate the chain: Before storing the chainsaw, clean and lubricate the chain.
Store the chainsaw in a dry place: This will prevent rust and corrosion.
Use a bar cover: A bar cover protects the chain and bar from damage.

Chain Inspection

Inspect the chain regularly: Look for signs of wear, damage, or loose rivets.
Replace worn or damaged chains: A worn or damaged chain can be dangerous.

Real-World Example: I once neglected to clean my chainsaw chain after cutting some particularly sappy wood. The pitch hardened on the chain, making it difficult to sharpen and reducing its cutting efficiency. I learned my lesson and now make sure to clean my chain after every use.

Key Maintenance Tips:

Keep the chain sharp: A sharp chain is a safe chain.
Lubricate the chain properly: Proper lubrication reduces friction and extends the chain’s life.
Maintain the correct chain tension: Proper tension ensures smooth and efficient cutting.

Takeaway: Regular maintenance is essential for keeping your chainsaw chain in top condition. A well-maintained chain will cut better, last longer, and be safer to use.

Safety Considerations When Sharpening and Using Chainsaws

Chainsaw operation and maintenance, including sharpening, can be dangerous. Prioritizing safety is crucial to prevent injuries.

Personal Protective Equipment (PPE)

Safety Glasses: Protect your eyes from flying debris.
Gloves: Protect your hands from sharp edges and splinters.
Hearing Protection: Chainsaws are loud and can cause hearing damage.
Chaps or Leg Protection: Protect your legs from accidental cuts.
Steel-Toed Boots: Protect your feet from falling logs and sharp objects.
Helmet: Protect your head from falling branches.

Safe Sharpening Practices

Secure the chainsaw: Ensure the chainsaw is securely held in a vise or on a stable surface.
Use the right tools: Using the wrong tools can damage the chain and increase the risk of injury.
Maintain a safe distance: Keep your hands and body away from the sharp edges of the chain.
Work in a well-lit area: Good lighting helps you see what you’re doing and reduces the risk of mistakes.

Safe Chainsaw Operation

Read the owner’s manual: Familiarize yourself with the chainsaw’s features and safety instructions.
Start the chainsaw on the ground: Never drop-start a chainsaw.
Use a firm grip: Hold the chainsaw firmly with both hands.
Keep your footing: Maintain a stable stance while operating the chainsaw.
Be aware of your surroundings: Watch out for obstacles, overhead hazards, and other people.
Never cut above your head: Cutting above your head is extremely dangerous.
Avoid kickback: Kickback is a sudden, uncontrolled movement of the chainsaw that can cause serious injury.
Use proper cutting techniques: Use the correct cutting techniques for the type of wood you’re cutting.

Kickback Prevention

Understand the kickback zone: The kickback zone is the upper portion of the chainsaw bar tip.
Avoid contact with the kickback zone: Never allow the kickback zone to contact any object.
Use a reduced-kickback chain: Reduced-kickback chains are designed to reduce the risk of kickback.
Maintain proper chain tension: Proper chain tension helps prevent kickback.

Personal Anecdote: I once witnessed a chainsaw operator experience a severe kickback. Fortunately, he was wearing proper PPE and was not seriously injured. However, the incident served as a stark reminder of the importance of safety.

Safety Checklist:

Have I read the owner’s manual?
Am I wearing proper PPE?
Is the chainsaw in good working condition?
Am I aware of my surroundings?
Am I using proper cutting techniques?

Takeaway: Safety should always be your top priority when sharpening and using chainsaws. By following these safety guidelines, you can significantly reduce the risk of injury.

When to Seek Professional Chainsaw Sharpening Services

While I’ve covered how to sharpen your chainsaw, there are times when it’s best to seek professional help. Knowing when to call in the experts can save you time, money, and potential frustration.

Signs You Need Professional Sharpening

You’re unable to achieve a sharp edge: If you’ve tried sharpening your chain multiple times and still can’t get it to cut properly, it may be time for professional sharpening.
The chain is damaged: If the chain has damaged cutters, bent links, or loose rivets, it may need to be repaired or replaced by a professional.
You’re uncomfortable sharpening the chain: If you’re not confident in your sharpening abilities, it’s best to leave it to the professionals.
You have a large number of chains to sharpen: If you have a lot of chains to sharpen, it may be more efficient to have them professionally sharpened.
You need specialized sharpening: Carbide-tipped chains and other specialized chains require specialized sharpening tools and techniques.

Benefits of Professional Sharpening

Expertise: Professional sharpeners have the knowledge and experience to sharpen chains quickly and accurately.
Specialized equipment: Professional sharpeners have access to specialized sharpening equipment that can achieve a sharper edge than manual sharpening.
Time savings: Professional sharpening can save you time and effort.
Cost-effectiveness: In some cases, professional sharpening can be more cost-effective than purchasing new chains.

Finding a Reputable Sharpener

Ask for recommendations: Ask friends, neighbors, or local hardware stores for recommendations.
Check online reviews: Read online reviews to get an idea of the sharpener’s reputation.
Look for certifications: Some sharpeners are certified by industry organizations.
Ask about their experience: Find out how long the sharpener has been in business and what types of chains they specialize in.

Personal Experience: I once tried sharpening a carbide-tipped chain myself and completely ruined it. I learned my lesson and now always take my carbide-tipped chains to a professional sharpener.

Cost Considerations: Professional chainsaw sharpening typically costs between $10 and $20 per chain. The cost may vary depending on the type of chain and the complexity of the sharpening job.

Takeaway: While it’s certainly possible to sharpen your own chainsaw chain, there are times when it’s best to seek professional help. Knowing when to call in the experts can save you time, money, and frustration.

Conclusion: Mastering Chainsaw Sharpening for Optimal Performance

Sharpening a chainsaw effectively, especially understanding and applying the “520-120” angles for Stihl chainsaws, is a skill that significantly impacts cutting efficiency, safety, and the lifespan of your equipment. From understanding the importance of top plate cutting angles and side plate angles to mastering the depth gauge settings, each aspect plays a crucial role in achieving optimal performance.

By investing in the right tools, following the step-by-step instructions, and prioritizing safety, you can ensure that your chainsaw is always ready to tackle any wood-cutting task. And if you ever feel overwhelmed or unsure, don’t hesitate to seek professional help.

Happy cutting, and stay safe!