What Size File for a Stihl MS 250 Chain? (3/16″ File Specs)
For the common STIHL MS 250 3/8-inch Picco chain, use a 5/32-inch (4.0 mm) round file. A 3/16-inch (4.8 mm) file is for .325-inch-pitch chain, not 3/8-inch Picco. Check the pitch stamped on your chain before filing: the saw model alone does not confirm the chain or file size.
A chain that burns wood instead of cutting cleanly is frustrating, and using the wrong file can make the edge worse. The quick check is simple: identify the chain pitch, choose the matching round file, then follow the sharpening angles listed for that chain. I check the chain markings first, even when a saw has its original bar. Bars and chains can be changed over time.
Equipment setup and safety prep
The right file depends on chain pitch, not just the MS 250 model name. Many MS 250 setups use 3/8-inch Picco chain and a 5/32-inch file; a .325-inch chain takes a 3/16-inch file. Confirm the chain and bar markings before you sharpen or buy a replacement.
Identify the chain before choosing a file
Pitch is the size class of the chain, measured from the distance between rivets; the chain maker’s stamped or printed code can help identify it. Gauge is different: it is the thickness of the drive links that fit into the bar groove. Neither measurement should be guessed from the saw’s model.
| Chain pitch | Matching round file | Typical MS 250 relevance |
|---|---|---|
| 3/8-inch Picco (low-profile) | 5/32 in (4.0 mm) | Common MS 250 setup |
| .325-inch | 3/16 in (4.8 mm) | Possible setup; verify chain marking |
The MS 250 is a 45.4 cc saw, commonly sold with a 16-inch bar, but bar and chain configurations can vary by market and may have been changed. A common setup has a .050-inch (1.3 mm) gauge, but check the bar and chain: pitch and gauge must match the bar and sprocket. Gauge does not determine round-file size.
Prepare the saw and work area
Before sharpening, turn the engine off, let the chain stop, and disconnect the spark-plug lead. Secure the saw so it cannot shift. Wear gloves and eye protection while handling the chain; for cutting, use a helmet, face and hearing protection, chainsaw chaps, and protective boots.
Before starting work, check your footing, escape route, overhead hazards, and the tree’s lean and loading. Keep bystanders clear. Follow the applicable manual and safety rules; hazardous tree work should be left to a qualified feller. Next step: read the pitch marking before selecting a file.
Field cutting and operation
A sharp, correctly tensioned chain cuts without being forced. Before each use, inspect the chain, brake, chain catcher, bar, and fasteners; set tension while the chain is cold according to the MS 250 manual. Use a chain that matches the bar and sprocket, and stop if it loosens, jumps, or fails to receive oil.
Check fit and tension before starting
Seat each drive link in the bar groove and around the sprocket. A chain with the wrong pitch or gauge may not fit correctly. Tension it as the manual directs: it should sit properly in the groove, with no sag, while still moving by hand when the brake is released. Do not check or adjust a moving chain.
Start the saw on clear, stable ground with the chain brake engaged. Once it is warm, confirm that the chain does not move at idle. If it does, stop and follow the manual’s troubleshooting steps; do not cut with a chain that moves at idle. Published MS 250 figures are about 2,800 rpm idle and 12,500 rpm maximum no-load, but use the manual for your market version. Do not tune by ear or exceed its specification.
Keep the brake engaged when starting and when moving between cuts. Use stable footing and a two-handed grip. Do not cut above shoulder height or operate one-handed. If the chain begins to loosen, jump, or stop receiving oil, shut the saw down and inspect it only after the chain has stopped.
A common bench-side mix-up is treating “MS 250 chain” as a complete chain specification. It is not. A replacement chain must match the bar and sprocket in both pitch and gauge, and its file size must match its pitch. Next step: verify fit, tension, and oiling before cutting.
Maintenance and sharpening/tuning
A round file restores the cutter edge; a depth gauge (also called a raker) controls how much wood each cutter takes. Use the file size and filing chart for the exact chain. Keep cutter angles and lengths consistent, then check depth gauges with a gauge made for that chain rather than using a universal assumed clearance.
File with the chain’s specified settings
Secure the saw with the engine off and spark-plug lead disconnected. Use a file holder suited to the chain. File cutters in alternating directions, keeping the holder’s guide marks aligned with the chain’s specified top-plate angle. Many STIHL chains use a 30-degree filing angle, but check the chart for your chain before relying on that value.
| What you find | What to use or check | What to avoid |
|---|---|---|
| 3/8-inch Picco stamped on chain | 5/32-inch (4.0 mm) round file | 3/16-inch file |
| .325-inch stamped on chain | 3/16-inch (4.8 mm) round file | Choosing by saw model alone |
| Gauge marking on bar or chain | Match it to the bar groove | Using gauge to choose file size |
| Chain-specific filing chart | Follow its angle and depth-gauge guidance | Assuming all chains share one setting |
Use light, even strokes and sharpen each cutter until its edge is clean; keep cutter lengths as even as practical. If a cutter is badly damaged or notably shorter than the others, follow the chain maker’s instructions or have the chain assessed. I do not try to compensate for uncertain file size by changing the filing angle.
After sharpening, check the depth gauges with the correct chain-specific gauge and lower them only as the chain maker specifies. The depth gauge affects the bite of the cutter; lowering it too far can make cutting rough and increase kickback risk. Do not file depth gauges by eye.
Check lubrication and fuel
Use proper bar-and-chain oil, and check that oil reaches the chain before cutting, following the saw manual’s test method. Oil delivery varies with conditions and setup, so there is no single flow-rate target that applies to every MS 250. Stop if the chain is not being lubricated.
For fuel, use a 50:1 gasoline-to-two-stroke-oil mix with suitable oil and fresh fuel. Follow the manual for the required gasoline and oil specifications and for fuel handling. Do not guess the ratio or use straight gasoline. Next step: match file, angle, and depth-gauge settings to the chain code.
Storage and seasonal care
Good storage starts with a clean, inspected saw and chain. Clear chips from the bar groove and oil holes, check the sprocket and chain for wear, and fit the chain guard before storing the saw securely. For longer storage, follow the STIHL manual’s fuel-system procedure and fuel-storage guidance.
Clean and inspect after use
With the saw shut down and cool, brush away chips and residue. Clean the bar groove and oil holes so debris does not block lubrication. Inspect the chain, bar, and sprocket for damage or wear; use the manual’s service guidance for replacement limits. Refit the chain guard before storage.
For storage beyond the period stated in the manual, follow STIHL’s instructions for the fuel system rather than leaving old fuel in the saw by default. Store fuel safely and follow local handling rules. Next step: check the manual before extended storage or service.
Quick answers
These short answers cover the file-size and chain-identification questions that matter before you sharpen an MS 250 chain. If a marking is unreadable or the chain appears to be a different type, identify it by its part number or ask a STIHL dealer before filing.
What file does a common MS 250 3/8-inch Picco chain use?
A 5/32-inch (4.0 mm) round file.
When is a 3/16-inch file correct?
For a .325-inch-pitch chain, when the chain maker’s filing chart specifies it.
Can I choose the file from “MS 250” alone?
No. Check the chain pitch or part number because the bar and chain may differ from the original setup.
Is chain gauge the same as pitch?
No. Pitch identifies the chain size class; gauge is drive-link thickness and must fit the bar groove.
Is .050-inch gauge common on an MS 250?
Yes, it is common, but verify the bar and chain markings. It does not determine the file size.
What filing angle should I use?
Follow the chart for your exact chain. Many STIHL chains use 30 degrees, but verify before filing.
Should I file the depth gauges every time?
Check them with the correct gauge after sharpening, and lower them only as the chain maker specifies.
What fuel mix does the MS 250 use?
A 50:1 mix with suitable two-stroke oil and fresh fuel, subject to the applicable manual’s fuel specifications.
What should I do if the chain comes loose or stops oiling?
Stop the saw, wait for the chain to stop, and inspect it before continuing. Do not retension or inspect a running chain.
What is the safest quick check before filing?
Read the pitch marking, select its matching round file, and confirm the chain-specific angle and depth-gauge instructions.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
