Sharpen a Chainsaw

Having a sharp blade on a chainsaw not only saves effort and wear on your equipment but makes using it safer. Besides, dull chains won't cut straight. Here are some tips for sharpening your own saw.

Steps

  1. Determine the size (or "gauge") of your saw's chain. You will need to buy either a rotary grindstone or chainsaw file that matches your chain tooth. Since there are several sizes of chainsaw teeth, the grindstone or file you choose must be the correct diameter for your saw. Typical sizes are 3/16, 5/32 and 7/32 of an inch in diameter.
  2. Clean the chain thoroughly. You may use mineral spirits or a commercial degreasing detergent to remove oil, dirt, and debris from your chain. Do not flood or get excessive cleaner on the engine or other components, since some of these products can damage the plastic housing or other parts.
  3. Inspect the chain for damaged or overly worn links and teeth. Individual teeth may become chipped, broken, or bent, making them dangerous to use. As a rule of thumb, the top plate (flat surface at the top of cutting teeth) should be at least {{safesubst:#invoke:convert|convert}} in length. If it is worn shorter than this, there is a risk it will break while in motion. Any damaged, weakened, or overly worn chains should be discarded.
  4. Set your saw on a solid surface or clamp the bar in a vise. The saw must be stable, and the blade must be firmly supported to permit safe and accurate filing. Clamping the bar in a vise, with the jaws holding the bar and allowing the chain to rotate freely, is your best option.
  5. Locate the leading cutter as your starting point. This will be the shortest cutter on the chain. If all of the cutters seem to be the same length, you may start anywhere. The main concern is that you file each cutter so that the flat edge on top of each cutter is very nearly the same length. That way each will slice away the same amount of wood as they pass through the kerf of your cut. It also may help to mark the first tooth you file with a dab of paint or a permanent marker so you'll be sure of where you started.
  6. Set your file in the notch on the front of the cutter. This is the angled "tooth" on the front of the flat surface of the chain link. The curve of the file should exactly fit the curve of the face of the cutting tip, and the top 20% of the file diameter should be above the top of the tooth.
  7. Hold the file at the same angle that the cutter was ground or filed to begin with. The angle might be 25 or 30 degrees (check saw specifications). Special "ripping" chains may have a flatter angle. In any case, it is essential to match the angle the chain was originally machined to. Some saw teeth have "witness markers" as a visual aid.
  8. Slide the file across the face of the cutter, using a moderate twisting motion to discharge metal chips (filings) that are removed. There is some difference of opinion as to the best direction for pushing the file, but usually you will push it from the short side of the angle toward the long point. This should leave a smoother cutting surface (an important consideration).
  9. Work every second tooth identically from your beginning point around the loop. As you progress through the chain, keep advancing it by hand so that the tooth you are filing is on top of the bar.
  10. Reverse sides of the saw and proceed around the unfiled teeth angled in the other direction. Keep an eye on the length of each flat top of the cutter. Some manufacturers suggest measuring with calipers to ensure an equal "bite" as the saw is cutting, but if you have a good eye, you should be close enough to get fairly good results.
  11. Check the clearance of the rakers (depth gauge), the curved hook shaped links between the cutters. They should clear each cutting edge about one tenth of an inch lower than the cutter. This governs the amount of wood that the cutter removes on each pass. A special tool that is laid on top of the blade is available from chainsaw dealers or hardware stores. If the gauge is too high and must be filed, this tool protects the adjacent tooth as you file the gauge down.
  12. File any raker/depth gauge that interferes with the cutter (in other words, that sits too high) using a flat mill bastard file (not likely to be needed except when dealing with a defective chain).
  13. Oil your chain (saturate/soak with oil), check the tension, and you should be ready to cut once again.



Tips

  • Check periodically for wear on the drive links, the blade groove, and sprocket. Chains can break and cause serious injury or death when operated with worn or damaged parts.
  • It is recommended that after a chain has been hand-sharpened five times, it should be ground by a chainsaw shop to correct any variations in tooth pitch that occurred during filing.
  • Buy the correct size file for your saw.
  • Use a chainsaw file guide to maintain the correct angle of your file stroke when filing your blade.

Warnings

  • If a chain is adjusted while hot, it may bind after cooling and require further adjustment.
  • It may not be necessary to use "brand name" chains. Store/distributor brands are made by many of those same companies, using the same design specifications. As you might expect, manufacturers do recommend using their own oil, chains and bars. If you use a chain with the correct pitch, gauge, and profile any time they are specified for a given task, you should have no problem.
  • Wear gloves and safety glasses/goggles during the sharpening process. You are dealing with extremely sharp edges, and without gloves you could easily cut yourself. When filing by hand, there's no need for goggles.
  • Manufacturers recommend checking and readjusting chains often, especially when first using a new chain (the break-in period). Oregon Chain recommends checking frequently during the first half-hour of use.
  • Do not force the chainsaw file. It could shatter if too much force is applied. A file the right size should slide across the teeth easily.
  • Not all chain bars are standard in how they are attached or adjusted, so be sure that those functions will work properly on your saw before buying a particular bar.
  • For best results, adjust chains when they are cool, as all chains tend to loosen (expand) in the heat of operation, even after the break-in period.
  • Never trigger the saw while sharpening the chain. Advance the chain only by hand during the sharpening process. For safety's sake, disconnect the spark plug wire before working on the chain.
  • New or sharpened chains always deserve careful treatment and use. It is recommended to fully saturate (soak) a new or reconditioned chain in the recommended oil.

Things You'll Need

  • Chainsaw file (correct size for your chain).
  • Flat mill bastard file.
  • File guide or gauge.
  • Safety equipment.
  • Wrench for adjusting your saw bar.
  • Cleaner and rags.

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Sources and Citations

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