Turning Archive 2005

Subject:
The turner's saw chain - super long

Mike Schwing from Md.
>Someone from AAW asked me if I could write an article on chainsaw sharpening for a woodturner. I tried. This is what I came up with. Please let me know what you think. It will be housed on the articles section on the AAW website when complete. Disclaimer - I claim no expertise in this field, only a little experience. Rather than violate copyrights and redraw images, and figuring this would be an online article, I made judicious use of links. Saved time and legal fees. Stihl, by the way, freely gave me permission to duplicate them for this article if I wished to do so.
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The Turner’s Saw Chain

This article is intended to be more about the actual saw chain than the chainsaw. The goal of it is to help give turners some easy to understand info about chain care.

Most woodturners own, or desire to own a chainsaw. Many own more than one. Most will admit to a lack of knowledge about how to care for a saw chain, including when and how to sharpen it. A few of my neighbors thought that chainsaws were self sharpening!

This article is divided up into a few topics; Defining characteristics of a chain, and care of your chain (including sharpening)

Construction of a saw chain
Typical chains are made of 3 main components – cutter, which usually includes depth gauge, drive link, and tie/bumper strap.

Good examples of each can be found here.. http://www.oregonchain.com/tech/ms_manual/ms_02.pdf

Defining a chain

The important characteristics which define a chain are pitch, chain length, and gauge. Pitch is defined as the distance between the centers of any 3 rivets divided by 2. Common pitches are ¼”, .325”, 3/8”, .404”, etc.. Gauge is the width of the drive link, it must match the width of the guide bar groove. Some examples of gauges are .043” (1.1mm) , .050” (1.3mm), .058” (1.5mm), etc.. Tie straps can be standard connectors or have special purposes to assist in minimizing kickback, etc..

Oregon Chain has an excellent online article depicting chain components and describing important terms. Find it here . http://www.oregonchain.com/tech/ms_manual/ms_02.pdf

Chains, bars, and oiling systems are all carefully matched on today’s saws. Stihl, for example, has special grooves in the drive links and in the bars that assist in moving lubricating oil around the bar. When selecting a new chain it is critically important that it be designed to match your guide bar, as well as in pitch, gauge, number of links, as well as sprocket.

Types of Chain.

The typical woodturner runs a chain known as a full complement – that is a chain that has opposing cutters placed every other link. This is a safe, reliable, fast cutting configuration, and helps in reducing kickback – a dangerous and frequently fatal condition where the saw suddenly and violently grabs and kicks back toward the operator.
“Skip” chains are also available that skip cutters at different ratios in favor of tie links. This reduces drag, and offers the possibility of faster cutting rates. It also presents greater opportunity for kickback as fewer cutters are in contact with the workpiece at any one time. At least two cutters need to be in a piece of wood to avoid kickback – one reason cutting small branches and twigs with the bar tip is so dangerous.
Rip chains are designed to cut wood with the grain and are ground in chisel configurations that are difficult to handle in a hand held saw. They are almost exclusively used in sawmill situations. I know of no one who would recommend a rip chain to a woodturner for cutting bowl blanks, nor anyone who uses one as such.

The links in the chain that do the actual cutting (cutters) are available in a bewildering array of choices. Most of them are of no real value for what we as turners typically do with a chainsaw. Chisel, semi chisel, square grind, micro, thin kerf, rapid, comfort, yadda yadda yadda..to name just a few. Some are even made with carbide cutters for special uses as in fire/emergency/rescue situations. They need to be ground with a special diamond grinding wheel, and are overkill for our needs. In reality, the chain that comes standard with a new saw will generally be more than sufficient for a turner’s needs, but you should have two. The standard equipment chain will likely be a semi-chisel type. Much discussion can be centered around cutter design and theory but it serves no real value for this article.

Care of your chain

Saw chain needs the same basic care that all of your edged tools require. Cutters get dull or damaged and need reshaping and sharpening. Bar guides wear unevenly and require retruing. Saps and oils and sawdust build up and require cleaning.

The cutters need to be sharp, but not quite so finely sharpened and honed as your favorite handplane’s blade. The proper file is generally sufficient. Chains may be sharpened by hand or by machine. Sawchain sharpening machines are generally out of the reach (and needs) of most woodturners, probably it is better and more rewarding to spend that money on a secondary chain, or a new gouge, or some finishing supplies. Most chainsaw service centers have machines that will automatically sharpen your chain. My experience has been that they do a good job, but not necessarily a better job than can be done by hand with practice. They are probably more accurate than doing it yourself with a handheld jig. The one drawback to them is that they remove more material than a hand sharpening, which will decrease chain life. Stihl recommends having your chain professionally ground after every 5th sharpening, as this will return them to proper dimensions and angles. A chain that has many or several teeth sharpened at different angles from each other will wander as it cuts and be difficult to control.

How do you recognize a dull chain?

A well sharpened and maintained chain will produce chips and shavings - a dull one will produce dust and smoke. A well sharpened chain will pull itself into a cut - a dull one will require manual feeding. A well sharpened chain will cut with its own weight - a dull one will require a great deal of effort applied to it. If you have used your saw for any length of time, it is ready for sharpening.

Chains get dull for the same reasons our other cutting tools do – wear. Some woods will cause them to wear more quickly than others. So will heat – dry wood will wear your chain more quickly, as will frozen wood. Lack of lubrication can exacerbate the problem, so keeping those oil channels clear is important, too. Probably the single quickest way to dull your chain to something that won’t cut butter is to touch it to the ground and cut into the earth. Avoid touching earth at all costs and develop cutting methods that do not require cutting into the ground. The moment you touch earth with your saw running, you will benefit from, and often require, sharpening immediately.

Sharpening

Before sharpening, it is important to inspect the chain for damage. The Oregon chain company has an excellent descriptor of chain damage and remedy. Find it here;
http://www.oregonchain.com/tech/ms_manual/ms_07.pdf
Stihl also has one - http://www.stihllibrary.com/pdf/SharpAdvice061301final.pdf

What tools do I use for sharpening?

Your choices are: (in all cases a properly sized/matched file/grinder is necessary)
1. Hand held file with no guide attachment. (OK in an emergency but not for regular use)
2. Hand held file with a guide attachment. This will allow you to “sight” the proper angle for sharpening and usually has a depth gauge adjuster included.
3. Hand held file in a bar mounted sharpening jig. Provides real, repeatable accuracy and very good results
4. Hand held Dremel type rotary tool with grinding wheel. Very important to use proper sized grinding tip.
5. Dremel type tool in a mounted sharpening jig.
6. Machine ground.

If you decide to employ any one of the first three suggestions, you will need to consult your chain specifications to find the appropriate size file. Most saw manufacturers have these lists online, or your service center can guide you. Some are available at the big box stores as well. The same thing goes for using a rotary tool.

So What Do I Sharpen?

The business end of the saw chain is the triangular point on the individual cutters. It does the majority of the work. As the cutter is fed into the wood, the point establishes (along with the depth gauge), the depth of the cut during each pass as well as beginning to carve out what will become the shaving or chip. If you were going to sharpen only one tiny piece of each cutter, that point would be the most important piece. There are 3 main angles that come into play to construct that point, and those angles all produce their own peculiar characteristics on saw performance. That discussion is outside the bounds and requirements of most woodturners’ needs. The remainder of the top chisel point is used to finish carving out the chip/shaving and help move it away from the workpiece. It is also important to sharpen this chisel and keep it free from damage.

Your sharpening for each cutter will be accomplished with a single type of stroke, and it will generally take 3-5 strokes of a file to sharpen a cutter that is not damaged. Each chain’s cutters have their own tooth angle, 30 and 35 degrees are common. Most file guides have those angles depicted for easy reference during filing operations.

Common/suggested filing steps

• Find the tooth that is “shortest” in top length (the “master cutter”). All other teeth should be ground to this length before sharpening. (I doubt many, indeed perhaps any, turners do this regularly if at all. I don’t either) Many sharpening guides/jigs have a scale for this on them. (This is from the Stihl sharpening guide)
• Start with the index tooth/colored tooth. Or mark the starting tooth with a marker.
• Looking from the front of the bar, head on, the file should be positioned so it makes the proper angle depending on your chain.
• Using the guide, (or if using a file with no guide, many individual cutters have a line etched on them to indicate the proper angle), line up the file in the other plane so that it cuts along the top edge of the cutter.
• File with cutting strokes in one direction only. The results will be cleaner/sharper and the file will last longer. Using a push stroke, move the file over the surface of the cutter. Relieve pressure, withdraw the file, and repeat this step 3 or 4 times. If you are unsure of your progress, you can first mark the cutting edge with a black marker. No evidence of marker should remain when you are filing properly.
• Move onto the next cutter in the same direction (skip a cutter) and repeat these steps.
• When you finish the last cutter one that side, turn the saw around and do the same to the other cutters, rather than switching hands or angles. By doing this you will be more likely to file the same angle, right or wrong on both sides. This is preferable to filing each side with even a slightly different angle. This would cause wander and difficulty controlling the cut.
• When each of the teeth has been sharpened on both sides, the next step is to pay attention to the depth guides/rakers. As the cutters get sharpened, they get shorter from top to bottom. If the depth guides are not filed down at the same rate, the thickness of each tooth’s cut decreases, increasing cutting time and effort required. It is technically possible to remove the depth gauge entirely, but practically this is dangerous and difficult to control. It should, rather, be filed down just enough to restore proper cutting depth. This is done with the aid of a depth guide.
• Slip the depth guide over the master cutter depth guide and file it down with a square file until it is level with the guide. This will flatten the profile of the depth gauge as it shortens it. When you are done filing each depth gauge, use the flat file to slightly round the front of each back to its original shape.

The above is, more or less, standard procedure for sharpening a chain by hand. It can be done in the shop or in the field. With practice, a 20” chain can be field sharpened in just a few minutes. Some people dress their chains in this manner with each filling of the gas tank. I field sharpen when I feel the need. This is usually when I notice I’m putting more effort into cutting, or seeing more dust than shavings, or smell burning. I stop and resharpen immediately upon touching ground, as every time I think I can do without I’ve proven myself wrong.

Several saw chain manufacturers, including Oregon, make bar mounted jigs that very accurately set the angles involved in chain sharpening, and allow for quick, accurate, and repeatable cutter sharpening. I find them extremely useful in the shop, but do not use this for field dressing a chain as it takes more time, and is one more thing to carry around.

A Few Words About the Guide Bar

Guide bars are not self servicing. They wear and become damaged, and if the oil channels are not kept clean proper lubrication of bar and chain become impossible. This leads to premature wear of both chain and bar.

It is important to inspect your guide bar for damage occasionally. Guidebar basics and troubleshooting, compliments of Oregon - http://www.oregonchain.com/tech/ms_manual/ms_08.pdf

Some of these occurrences can be repaired. A nicked bar can be filed, but it VERY important to keep the sides perpendicular to each other. Bars should also be kept clean of debris that can tend to build up in the channels. Soaking in a solvent occasionally will help loosen debris, and a wire brush will remove them from the channels.

Below are some very good sources of chain and bar info as well as reordering/supplies;

Bailey’s – chainsaw and accessories supplier http://baileysonline.com/
Oregon saw chain/bars http://www.oregonchain.com/index.htm
Stihl – http://stihlusa.com
Husqvarna - http://www.usa.husqvarna.com/

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