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Few tree care professionals would disagree that one of the most frustrating experiences in their daily work life can be oiling and fueling a chain saw, have it start readily and run well, yet once the chain touches the wood it appears to be removing wood at the pace of a tired elderly carpenter ant with poorly fitting dentures.

Chain Saw Sharpening

By Michael “House” Tain


Few tree care professionals would disagree that one of the most frustrating experiences in their daily work life can be oiling and fueling a chain saw, have it start readily and run well, yet once the chain touches the wood it appears to be removing wood at the pace of a tired elderly carpenter ant with poorly fitting dentures.

Obviously, poorly sharpened chain saws are an efficiency issue on a professional tree crew — creating lost time in wood cut either far too slowly or in interesting shapes — but they are also a safety issue. Beyond the simple fact that irritated chain saw operators are probably not focusing on what they should be — the cutting they are doing with the chain saw itself — poorly sharpened saws take a toll on the operator’s body, creating muscle fatigue and other physical issues that could easily result in the operator not having the strength, reaction time, or remaining energy reserves to react or deal with an unexpected occurrence.

Additionally, a dull chain that takes longer to complete a cut or an improperly sharpened chain that makes it difficult to line up cuts precisely can both lead to an operator being in a dangerous position or situation for too long — resulting in tragic consequences. The most ready solution to this problem is properly sharpened and maintained chain saws; yet chain saw sharpening/maintenance opinions are much like vacuums — everyone seems to have one and there is a fair amount of variety.

Properly sharpening a chain saw requires attention to detail and consistency of both of angles and pressure, along with an understanding of how a cutter tooth on a chain removes wood. A lack of knowledge or ability in any of these areas can make cutting with a newly “sharpened” chain saw a frustrating experience.


Depth gauges

The depth gauge, sometimes referred to as the “raker” or “drag,” is one of the most important areas in sharpening a chain saw effectively. But it is also the one most often neglected or ignored, possibly due to the fact that, to the casual eye, it may seem to have nothing to do with the angles or cutting surfaces of the tooth — yet it plays a role of vital importance. The depth gauge determines how large a “bite” the cutting part of the tooth takes, so it must be filed or tuned in conjunction with the cutting parts of the tooth. If the depth gauge has never been touched while the cutting surfaces of the tooth have been filed again and again to perfection, the saw will cut poorly (if at all), emitting a cloud of fine sawdust as the tops of the depth gauges gnaw away at the wood fiber. The untouched or “untuned” depth gauges are preventing the finely sharpened cutter teeth from ever coming into contact with the wood or getting any “bite” at all. Conversely, if the depth gauges have been taken down too much in relation to the cutter teeth, they will be getting too large a “bite.” This causes at least vigorous chattering and vibration while cutting in hardwoods, and often leads to vicious kickbacks as the too large “bite” stops the chain for an instant, causing it to attempt to turn within the chain, and throwing it back toward the operator. Either variation of depth gauge, untouched or touched too much, is unacceptable for safe, efficient cutting, but both are easily remedied through the use of a depth gauge guide. These simple tools allow the sharpener to easily “tune” each depth gauge to its particular cutter tooth with a flat file, assuring the proper distance exists, and generating the efficient removal of a nicely formed chip of wood.


Cutter teeth

The cutter teeth — the ones that actually remove the wood after being properly set up by their respective depth gauges — are the workhorses of a finely tuned chain, repeatedly chiseling out chip after chip of wood as the cut is made. The point or starting corner of the tooth begins the cut by entering the wood, the top plate and attendant angle begins to chisel a chip of wood down into the gullet as the side plate of the tooth separates it. Interestingly enough, this design for modern chain saw teeth is based on observations made by a logger of a beetle’s jaws and teeth in removing wood, while the fellow was on his lunch break. This logger, Joe Cox, later went on to found Oregon Cutting Systems. Close observers will notice that the width of a well-formed chip is consistent with the distance from the outer edge of a right-hand cutter to the outer edge of a left-hand cutter, as both work together to fully sever the chip. A tooth that has been damaged by contact with a material other than wood, such as dirt or stone, or one that has become severely dull will exhibit a shiny area along the front edge. A starting point for sharpening is realizing that the tooth will need to be filed until that shininess has been removed. Severely damaged teeth may be more quickly sharpened by removing this area with a flat file prior to even beginning with a round file and guide. Many tree care professionals have their own personal opinion on the best angle to file the top plate at, yet chain manufacturers themselves — after spending millions of dollars on research and development — give fairly specific guidelines on angles for each of the individual types of chains they produce. The choice of angle is obviously up to individual users, because they have that file in their sweaty sap-sticky hands, but the typical angles from manufacturers range from 25 to 35 degrees, dependent on type of chain and projected use. Once again, the use of any of a variety of guides will ensure consistency and accuracy in sharpening the cutter teeth. There are file guides that simply hold the file and provide the angle; roller guides that have a built in depth gauge guide, providing two tools in one; and file guides that hold the round file, provide the angle, and hold a flat file that files the depth gauges at the same time. Personal preference will dictate which file guide works best for individual users, but some form of guide will definitely improve the efficiency of the sharpening process and the cutting action of the chain.


General sharpening guidelines

The appropriate-sized file should always be used for individual chains, as files that are too small or too large will not only incorrectly sharpen the chain, but also damage and possibly weaken the structure holding it all together. This information should be available from the manufacturer or on the box the chain comes in, but a general rule is that the correctly sized file should protrude 20 percent or 1/5 above the cutter tooth. Cutter teeth should be filed from the inside of the bar out, and, for efficiency, all teeth sharpened on one side prior to filing the other. The typical filing process would begin with sharpening all the cutter teeth using an appropriate file and gauge; and afterward, unless an “all in one” guide has been used, going through with the appropriate depth gauge guide and a flat file and “tuning” each depth gauge to each cutter tooth. Bench vises or in-the-field stump vises will hold the bar and saw immobile during the sharpening process while still allowing the chain to rotate freely. Sharpeners having difficulty remembering which tooth they started with might use a marker to darken the first tooth sharpened, or some chains may provide two right- or left-hand cutters in a row as an easy starting/ending point. Many cutter teeth currently available have a diagonal line running across the top plate at the rear of the cutter. This is known as the witness mark; and though it is intended to inform the user of when to take the chain out of service, it also tends to match the desired angle to file the tooth at, thus providing a visual guide for sharpeners. The use of bench or electric grinders in the sharpening operation can be quite advantageous, as it will speed the process, but tree care personnel who choose this method must be very aware of the grinder’s proper use and set up. The use of the appropriate stones and angles is paramount, as chains are easily ruined or destroyed if sharpened with a grinder improperly set up. Additionally, grinder operators must pay close attention to the amount of time the grinding wheel or stone is in contact with the tooth, as it is very easy to overheat the metal, causing it to lose its “temper” — and creating a tooth that will be impossible to further sharpen with a round file. Chain saw operators who believe they have sharpened the teeth and depth gauges correctly yet still find the cut curving may wish to check the bar for bends or distortions. These bends typically occur when the bar is pinched or caught in a cut and the operator uses excessive force to remove it. The straightness of the bar may be easily discovered by laying it on a flat surface and ensuring it lays flat; or by looking down the rails from one end to the other, and making sure daylight can be seen.


New technology

One of the most exciting new tools available to tree care industry professionals is the PowerSharp system from Oregon. Designed, developed, and tested by Oregon Cutting Systems, this new tool allows the arborist to sharpen chain saw chain quickly and easily on the ground or even aloft with no need for guides, files or vises. In short, the system uses a special bar and chain on the saw, with an attendant sharpening device that can fit in the pocket of the user’s chaps or chain saw pants, or even hang off a climber’s harness. The chain and stone inside the bar-tip-sharpening device are a matched pair, and are designed to be replaced together. The dull saw is turned off, the device easily mounted or latched onto the tip of the bar, the saw started, and, at full throttle, the plastic foot at the front of the device pushed lightly against a firm surface such as the trunk or branch of a tree. Operators should keep the saw between their knees and waist when sharpening; and never reach above shoulder height (just as when cutting with a chain saw). The sharpener only needs to be pushed against the solid object for three to five seconds to sharpen the chain well, and a small amount of sparks and smoke will be visible. From personal experience, one round of sharpening will be sufficient for most normally dulled chains; but if the operator has been “digging for clams” with their saw, additional sharpening may be required. The saw should be turned off, the sharpening device removed and stowed, a test cut made, and additional sharpening done if needed (but in most cases that won’t be necessary). The chain and stone should be replaced together, as mentioned previously, and the need for replacement will become apparent when saw cutting performance decreases with no improvement from sharpening, or there are very little or no sparks during the sharpening process. This system uses a completely different chain, so operators should not attempt to sharpen a PowerSharp chain with a traditional file, or sharpen a standard chain with a PowerSharp system. (Note: Efco, a chain saw manufacturer, recently announced that three of its saw models will come from the factory equipped with the PowerSharp system.) Although it might take a small amount of getting used to for experienced climbers and cutters, the system has the capability to revolutionize chain saw sharpening in the tree care industry if used correctly and appropriately — saving time, energy and effort. In addition, the ease of use of the PowerSharp system should eliminate much of the fussing and bickering that goes on in tree crews about “who” sharpened this saw, as the system can easily be used by a brand new branch manager with a minimal amount of explanation and training.


By following these few basic guidelines and techniques — and perhaps trying some of the new technology — most chain saw operators should find their frustration levels, saw downtime and blood pressure reduced at least slightly, while their cutting efficiency and safety increases.


Michael “House” Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions www.northamericantrainingsolutions.com and Arbor Canada Training and Education www.arborcanada.com  He is currently located in Lancaster, Ky., and can be reached via e-mail at house@houseoftain.com

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