How to Sharpen a Chainsaw Chain
A sharp chainsaw chain cuts quickly with moderate throttle and produces clean wood chips. A dull chain requires full throttle for slow progress and produces fine sawdust rather than chips. Sharpening a chain takes five to ten minutes and restores cutting performance to near-new levels. Every homeowner who uses a chainsaw regularly should be able to do this.
What You Need
Round file: The diameter must match the chain pitch. Common chain-to-file pairings:
- .325-inch pitch chain: 3/16-inch (4.8mm) file
- 3/8-inch pitch chain: 7/32-inch (5.5mm) file
- .404-inch pitch chain: 7/32-inch or 13/64-inch (5.2mm) file
Check your chain specification (printed on the chain packaging or stamped on the drive links) to confirm pitch. Using the wrong file diameter over-files or under-files the cutter profile.
Flat file: For depth gauge adjustment.
Depth gauge tool (raker gauge): A flat template that sits over the cutter and shows how much the depth gauge (raker) protrudes above the correct height. Available from chainsaw supply shops.
File handle: A handle that clamps the round file and often incorporates angle guides.
Filing the Cutters
Each cutter on the chain has three dimensions that matter for cutting performance: the top plate angle, the side plate angle, and the depth gauge height. Filing restores the top and side plate angles; the depth gauge is addressed separately.
Step 1: Engage the chain brake and clamp the bar. Secure the saw in a vice or against a stable surface. The chain must not move during filing. Engaging the chain brake locks the chain.
Step 2: File each cutter. Position the round file in the curved hook of the cutter at the correct angle. Most chains use a 30-degree top plate angle and a 60-degree side plate angle relative to the bar. File guides simplify maintaining these angles if you are new to chain sharpening.
Hold the file so approximately 20 percent of its diameter extends above the top plate of the cutter. Apply forward pressure on the push stroke only; lifting the file on the return prevents the teeth from dulling the file. Count strokes per cutter: use the same number on every cutter (typically 3 to 5 strokes for routine sharpening) to maintain consistent cutter height across the chain.
Step 3: Sharpen alternate-side cutters separately. Cutters alternate left and right around the chain. Sharpen all the cutters on one side (say, all the left-facing cutters) from one position, then rotate to the other side and sharpen the right-facing cutters. This maintains consistent angle without repositioning for each cutter.
Visual check: A correctly filed cutter has a bright, shiny leading edge with no visible flat spot or rounded zone at the tip. A dull cutter has a visible silver-gray flat zone on the leading edge from wear.
Adjusting Depth Gauges
The depth gauge, or raker, sits in front of each cutter and controls how deeply the cutter bites into the wood with each pass. As the cutters are filed shorter over multiple sharpenings, the depth gauges become proportionally too tall and reduce cutting aggression.
Place the depth gauge tool flat over the chain. Any depth gauge that protrudes above the template must be filed down with the flat file until it is flush with the template surface. Apply light strokes with the flat file across the top of the depth gauge only. Round the leading edge of the depth gauge very slightly after filing to prevent it from catching on the wood.
Depth gauges need adjustment approximately every third to fourth sharpening on average, less frequently than cutter sharpening.
When to Replace the Chain
A chain that has been sharpened many times and whose cutters are noticeably shorter than when new, or one that has suffered a ground strike (contact with soil, rock, or other abrasives), may be too worn or damaged to sharpen back to useful performance. Ground strikes blunt the entire chain in seconds and often require replacement rather than hand sharpening to restore acceptable cutting speed.
A good chain should give at least 5 to 10 full sharpenings across its life before the cutter height is reduced to the point where replacement is warranted.
For the correct chain installation direction after removal for sharpening, the chainsaw chain direction guide covers cutter orientation and tension adjustment after reinstallation.